9- fixed bug in detection of double lex matrices due to wrong memory allocation
10- fixed bug where parameter `limits/objectivestop` was copied to subscips in plugins which have different objectives
11- in count mode respect empty solution when problem is solved in presolving
12- fixed that SCIP may have tried to pass a negative random seed to an LP solver
13- fixed bug where conflict analysis in strong branching tried to analyze an unsuccessful LP solve
14- enable parameter limits/restarts by allowing to reach the restart limit in restartAllowed()
15- handle normalizing linear constraints in presolving with more caution to avoid numerical difficulties for integer variables with large coefficients
16- use quad precision to calculate residual activity bounds to reduce numerical errors for large variable bounds in cons_linear.c
17- in SCIPsolveProbingLP() when objective has been changed do not return cutoff due to exceeding the cutoff bound
18- set probing LP to be a relaxation only when objective has not been changed
19- declare contradicting infinities in getMinActivity() and getMaxActivity() as non-tight
20- reject farkas solution with large values to bound magnification of errors in SCIPgetFarkasProof()
21- if all variables are fixed, apply relative feasibility tolerance to avoid invalid infeasibility in applyFixings() of cons_linear.c
22- delete empty redundant knapsack and linear constraints after cleanup in SCIPmatrixCreate()
23- cleanup first constraints in SCIPcleanupConssVarbound(), SCIPcleanupConssSetppc(), and SCIPcleanupConssLogicor()
24- symmetry handling methods have not been added immediately after computing symmetries, which has been fixed
25- delay checking node limits after presolving to correctly continue up to the exceeding main node
26- simplified the objective sense assumption for the subproblems in the Lagromory separator
27- update effective root depth iteratively to avoid trapping it at a single child node
28- fixed that dualsparsify presolver did not always check do-not-multiaggregate variable flag
29- fixed bug in computing elements of orbits in orbital reduction
30
31Miscellaneous
32-------------
33
34- redefine isrelax to istight in cons_linear.c
35
36Build system
37------------
38
39### Cmake
40
41- A file cmake.log containing the changed options is written to the cmake build directory.
42- removed replacement of the settings of RelWithDebInfo
43- add compile option -ffp-contract=off or /fp:precise to enhance reproducibility across different systems
44
45### Makefile
46
47- add flags -ffp-contract=off and /fp:precise to enhance reproducibility across different systems
48
49Interface changes
50-----------------
51
52### New parameters
53
54- added parameter "propagating/symmetry/symtiming" to determine when symmetries are computed and handled
55
56### Changed parameters
57
58- Disabled "propagating/symmetry/addconsstiming" since it is not used anymore.
59- Disabled "propagating/symmetry/ofsymcomptiming" since it is not used anymore.
60
61@section RN900 SCIP 9.0.0
62*************************
63
64Features
65--------
66
67- added simplification of abs(x)^n to x^n when n is even (simplify rule POW12)
68- in expression simplification, added possibility to expand power of sum with exponents larger than 2 (simplify rule POW7)
69- in expression simplification, added possibility to expand products with sums as factor when there are more than two factors (simplify rule SP12b)
70- in expression simplification, added possibility to allow expanding power of products with fractional exponent (simplify rule POW5a)
71- can now build with Lapack (used for solving nonlinear problems) explicitly; if IPOPT is used, then Lapack is accessed through it;
72 an interface to Lapack is available in lapack_calls.h
73- added support for logical constraints in binary variables and basic logical operators (and, or, not, equal) to AMPL .nl reader
74- indicator constraints now use the same slack variable for the linear constraints if binary variables are used multiple times
75 for indicator constraints
76- new diving heuristic indicatordiving that focuses on indicator variables which control semicontinuous variables
77- updated statistics on NLP relaxation; information on convexity of NLP has been added
78- added new bandit method (EXP.3-IX) that is the new default of the ALNS heuristic
79- added dialog to display recognized permutation symmetries ("display symmetry")
80- The symmetry detection code has been completely restructured. Instead of completely encoding symmetry information in
81 prop_symmetry.c, there is a new callback for constraint handlers, which returns symmetry relevant information by
82 encoding a constraint as a node and edge colored graph. This way, also custom constraint handlers can provide
83 symmetry information.
84- added special presolving step for logicor and set covering/packing for constraints with two variables and one independent variable
85- increased the depth field of the tree structure from 16 to 30 bits and the max depth of the search tree from 65534 to 1073741822
86- added new cut selector plugin called cutsel_ensemble. Performs a superset of hybrid cutsel. Implements new filtering methods and scoring options.
87- added new branching rule based on Gomory mixed-integer cuts
88- added new branching score to the reliability pseudo-cost branching rule
89- added new cut selector plugin called cutsel_dynamic. Performs a superset of hybrid cutsel. Implements new filtering methods and scoring options.
90- added monoidal strengthening to intersection cut generation of nlhdlr_quadratic
91- extended heuristic dps to run after processing the node and to use strict limits for the reoptimization step
92- extended obbt propagator to handle variables of the linear constraints corresponding to indicator constraints
93- added new heuristic heur_scheduler that models the selection of LNS and diving heuristics as a multi-armed bandit problem
94- added nonlinear handler for signomial expressions: adds cuts based on a difference of convex functions representation
95- Delayed separators are now called if no other cuts have been found. Previously, such separators were only called near stalling or when the separation rounds limit was reached.
96- added a new separator sepa_lagromory to generate Lagromory cuts in a relax-and-cut framework, i.e., GMI cuts generated
97 at different bases that are explored in the process of solving the Lagrangian dual problem at a node. This separator
98 is OFF by default.
99- when parsing nonlinear constraints from CIP files, the * after the number in a term is now optional if followed by a variable,
100 i.e., instead of 3*<x>*<y>, now also 3<x>*<y> can be read, but 3<x><y> is not supported;
101 this allows to read some CIP files that were written with SCIP < 8
102- when running bliss, we now limit the number of actually created generators and not the ones considered by bliss
103
104Performance improvements
105------------------------
106
107- Variable conflict-based addition of Schreier-Sims cuts for symmetry handling in prop_symmetry.c does no longer use
108 an expensive explicit conflict graph construction.
109- Only run propagation of indicator constraints if relevant variables have changed.
110- Propagation of indicator constraints propagates maximal activity of linear constraint to upper bound of slack variable.
111- Added initialization of LP relaxation for SOC constraints.
112- Avoided some numerical issues when separating SOC constraints.
113- If differentation of convex expression fails in convex nlhdlr, then a perturbed point is tried.
114- Use sassy/bliss as default symmetry computation package.
115- No longer linearize indicator constraints in undercover heuristic by default.
116- Deactivate pre-root heuristic zeroobj in undercover heuristic.
117- Added new branching score tiebreaker for reliability pseudo-cost branching rule
118- Try nearest bound if zero solution value is out of bounds in heuristic trivial.
119
120Interface changes
121-----------------
122
123### New and changed callbacks
124
125- Added solution linearization callback for nonlinear handlers.
126 The nonlinear handler may use this callback to add tight cuts that use the given solution as reference point to the cutpool.
127 The callback is called if option constraints/nonlinear/linearizeheursol is enabled.
128- The callback for copying problem data SCIP_DECL_PROBCOPY() now has a parameter "original" indicating whether the original
129 or transformed problem should be copied. Similarly, SCIPprobCopy() in prob.h/c has such a parameter.
130- Added CONSGETPERMSYMGRAPH and CONSGETSIGNEDPERMSYMGRAPH callback for constraint handlers, which provides symmetry information about constraints to SCIP.
131
132### Deleted and changed API methods
133
134- SCIPtpiInitLock(), SCIPtpiDestroyLock(), SCIPtpiInitCondition(), SCIPtpiDestroyCondition() now take a double
135 pointer to SCIP_LOCK/SCIP_CONDITION, respectively.
136- Renamed SCIPtpiSumbitJob() to SCIPtpiSubmitJob().
137- SCIPcreateConsIndicatorLinCons(), SCIPcreateConsIndicatorGenericLinCons() do not allow binvar to be NULL anymore
138- Replaced SCIPnlrowSetCurvature() by SCIPsetNlRowCurvature().
139- SCIPsnprintf() now returns the required string length in case reallocation is necessary.
140- SCIPcomputeCoverUndercover() receives three more arguments which nonlinearities to cover
141- removed definition of SQRT
142- SCIPincludeObjConshdlr(), SCIPincludeConshdlr(), SCIPconshdlrCreate() receive two more arguments for the
143 conshdlr callbacks CONSGETPERMSYMGRAPH and CONSGETSIGNEDPERMSYMGRAPH
145- new parameter issigned for SCIPcomputeOrbitsSym()
146- new parameter symtype for SCIPcomputeComponentsSym()
147- new parameter symtype and permvardomaincenter for SCIPlexicographicReductionAddPermutation()
148- replaced parameters matrixdata and exprdata of SYMcomputeSymmetryGenerators() by graph
149
150### New API functions
151
152- new functions for interfacing with Lapack: SCIPlapackIsAvailable(), SCIPlapackIsAvailable(), SCIPlapackComputeEigenvalues(), and SCIPlapackSolveLinearEquations
153 These functions should be used instead of SCIPisIpoptAvailableIpopt(), SCIPcallLapackDsyevIpopt(), and
154 SCIPsolveLinearEquationsIpopt() in the context of computing eigenvalues or solving linear equations.
155 If IPOPT is available, the calls will be passed on to Ipopt's interface to Lapack.
178- SCIPincludeCutselEnsemble(), SCIPselectCutsEnsemble() to include cutsel_ensemble or use the selection algorithm
179- SCIPincludeBranchruleGomory() includes new gomory cut based branching rule
180- SCIPgetVarAvgGMIScore(), SCIPincVarGMISumScore(), SCIPgetVarLastGMIScore(), SCIPsetVarLastGMIScore() set historical values used by SCIP's default branching rule
181- SCIPincludeNlhdlrSignomial() includes the signomial nonlinear handler
182- SCIPgetExprMonomialData() returns a monomial representation of a product expression
183- SCIPestimateRoot() computes estimators for roots with exponent in [0,1]
184- SCIPincludeCutselDynamic(), SCIPselectCutsDynamic() to include cutsel_dynamic or use the selection algorithm
185- SCIPincludeSepaLagromory() to include the new Lagromory separator
186- SCIPconsCompCheck() to compare two constraints based on their check priority
187- SCIPgetConsPermsymGraph() and SCIPgetConsSignedPermsymGraph() to access the (signed) permutation symmetry detection graph of a constraint
188- SCIPsetConshdlrGetPermsymGraph() and SCIPsetConshdlrGetSignedPermsymGraph() to set the (signed) permutation symmetry detection graph of a constraint
189- SCIPconshdlrSupportsPermsymDetection() and SCIPconshdlrSupportsSignedPermsymDetection() to access whether a conshdlr supports detection of (signed) permutation symmetries
190- new API functions for creating and manipulating a symmetry detection graph: SCIPcreateSymgraph(), SCIPfreeSymgraph(), SCIPcopySymgraph(), SCIPextendPermsymDetectionGraphLinear(),
222 String values should not be quoted and spaces in string values are not supported.
223- sassy can be used now as preprocessor for nauty/traces
224- The solution status codes written to AMPL solution files now match those from https://mp.ampl.com/details.html#_CPPv4N2mp3sol6StatusE.
225
226### Changed parameters
227
228- change default value of parameter separating/filtercutpoolrel to FALSE
229- Shrunk range of parameter "propagating/symmetry/sstleaderrule" from [0,3] to [0,2], removed "MAXCONFLICTS"-option.
230- Removed reading/gmsreader/freeints. A default upper bound of +inf is now assumed for integer variables in GAMS (which is the case since GAMS 23.1).
231- Disabled "propagating/symmetry/symfixnonbinaryvars" since it is not used in the new symmetry code.
232- Replaced "propagating/symmetry/onlybinarysymmetry" with "propagating/symmetry/enforcecomputesymmetry" and set to FALSE by default.
233- Disabled "propagating/symmetry/performpresolving" since running orbital reduction during presolving is not effective.
234- Repurposed "propagating/symmetry/usedynamicprop" since it now also applies to lexicographic reduction.
235- Changed default value of parameter "propagating/symmetry/addsymresacks" from FALSE to TRUE.
236
237### New parameters
238
239- separating/maxcutsgenfactor and separating/maxcutsrootgenfactor as factors (w.r.t. separating/maxcuts and
240 separating/maxcutsroot) for limits on the number of cuts generated (which used to be constants '2')
241- expr/pow/expandmaxexponent to specify limit on exponent when to expand power of sum
242- expr/pow/distribfracexponent to enable expanding power of products with fractional exponents
243- expr/product/expandalways to enable expanding any product with sums as factor (that is, also when more than two factors)
244- nlhdlr/convex/maxperturb to specify maximal perturbation of non-differential reference points
245- benders/default/nlpiterlimit to adjust iteration limit for NLP solver for Benders' decomposition NLP subproblems
246- limits/objectivestop to interrupt the solve as soon as a primal solution is found
247 that is at least as good as the given value
248- heuristics/undercover/{coverand,coverind,covernl} to control which nonlinearities to consider (by default only "and" and nonlinear constraints)
249- cutselection/ensemble/∗ all parameters for new ensemble cut selector
250- cutselection/dynamic/∗ all parameters for new dynamic cut selector
251- branching/relpscost/gmiavgeffweight specifies the weight in the relpscost branching score of the normalized efficacy of all generated GMI cuts (for a variable)
252 branching/relpscost/gmilasteffweight specifies the weight in the elpscost branching score of the normalized efficacy of the last generated GMI cut (for a variable)
253- nlhdlr/quadratic/usemonoidal to enable monoidal strengthening when separating quadratics with intersection cuts
254- nlhdlr/quadratic/trackmore to collect more statistics for monoidal strengthening when separating quadratics with intersection cuts
255- nlhdlr/quadratic/useminrep to use the minimal representation to compute cut coefficients when separating quadratics with intersection cuts
256- nlhdlr/quadratic/sparsifycuts to enable sparsification of intersection cuts for quadratics
257- heuristics/dps/reoptlimits to set strict limits for the reoptimization step in dps
258- heuristics/dps/timing to run dps after processing the node
259- heuristics/scheduler/∗ all parameters for new scheduler heuristic
260- nlhdlr/signomial/enabled, nlhdlr/signomial/maxnundervars, nlhdlr/signomial/mincutscale: parameters for the signomial nonlinear handler
261- separating/lagromory/freq to denote the frequency for calling Lagromory separator
262- separating/lagromory/away to denote the minimal integrality violation of a basis variable to try separation
263- separating/lagromory/dynamiccuts to denote whether the generated cuts be removed from LP if they are no longer tight
264- separating/lagromory/maxroundsroot to denote the maximal number of separation rounds in the root node
265- separating/lagromory/maxrounds to denote the maximal number of separation rounds in a non-root node
266- separating/lagromory/nmaxcutsperlproot to denote, in the root node, the maximal number of Lagromory cuts that can be
267 separated per explored basis of the Lagrangian dual
268- separating/lagromory/nmaxcutsperlp to denote, in a non-root node, the maximal number of Lagromory cuts that can be
269 separated per explored basis of the Lagrangian dual
270- separating/lagromory/perroundnmaxlpiters to denote the maximal number of separating LP iterations that are allowed per
271 separation round
272- separating/lagromory/dualdegeneracyratethreshold to denote the minimum dual degeneracy rate for the separator execution
273- separating/lagromory/varconsratiothreshold to denote the minimum variable-constraint ratio on the optimal face for the
274 separator execution
275- many other advanced parameters for the Lagromory separator, which are also mentioned under separating/lagromory/∗
276
277### Data structures
278
279- new data structure SYM_GRAPH to encode symmetry information from a constraint
280- new data structure SYM_EXPRDATA to encode symmetry information from expressions
281- replaced enum SYM_SYMTYPE by a complete new one; removed SYM_RHSSENSE, added SYM_NODETYPE and SYM_CONSOPTYPE
282
283Deleted files
284-------------
285
286- deleted the now unused files: tpi_none.h, tpi_openmp.h, tpi_tnycthrd.h, type_tpi_none.h, type_tpi_openmp.h, type_tpi_tnycthrd.h
287
288Unit tests
289----------
290
291- new unittests for nlhdlr_quadratic that test monoidal strengthening and the use of the minimal representation to compute cut coefficients
292- unittests for nlhdlr_signomial
293
294Testing
295-------
296
297- changed `set lim obj` to `set lim objective` in ctest since `obj` is no longer unambiguous
298
299Build system
300------------
301
302### Cmake
303
304- New flag -DLAPACK=on for linking with Lapack (must be available in the system)
305- added flag option "SYM=sbliss" for using sassy/bliss as a graph automorphism package
306- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP.
307- added flag option "SYM=snauty" for using sassy/nauty as a graph automorphism package
308
309### Makefile
310
311- added flag option "nauty" for SYM variable to specify which graph automorphism package should be used
312- added flag option "sbliss" (sassy/bliss) for SYM variable to specify which graph automorphism package should be used
313- added flag option "snauty" (sassy/nauty) for SYM variable to specify which graph automorphism package should be used
314- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP
315- New flag LAPACK for linking with Lapack (must be available in the system)
316- A file scip/config.h is created in the build directory ($(OBJDIR)/include) now.
317 Defining NO_CONFIG_HEADER is no longer necessary and has no effect anymore.
318
319Fixed bugs
320----------
321
322- Number of runs in which separation is enabled will now be correct as per "separating/maxruns" parameter. Earlier,
323 separation was enabled for "maxruns + 1" number of runs, i.e., separation was enabled even when "maxruns = 0" was set.
324- add safeguard for number of selected cuts
325- use double double precision for delta in activity updates of cons_linear.c
326- sort constraints in checkSolOrig() to keep the logic of constraint handlers intact
327- fixed make install when SHARED=no and make uninstall
328- check absolute coefficients relative to extremal average to avoid invalid unifications in normalizeCons()
329- enforce and check symmetry-based constraints to take their locks (in dual reductions) into account
330- flush changes at the end of SCIPlpiSetBase() in lpi_grb.c to apply the newly set basis correctly
331
332Miscellaneous
333-------------
334
335- The TPI has been changed to become mostly independent from the actual parallel interface during compile time.
336 For this, the locks and conditions are now pointers to abstract structs.
337- fixed that scip/def.h, the header for C preprocessor definition (#define's), included headers for some SCIP type and function definitions
349- fixed that scaling of rows in Gurobi interface (SCIPlpiScaleRow()) changed infinite sides to large finite ones (1e20) when scale factor is negative
350- check whether objective limit is truly reached in SCIPlpiIsStable()
351- if an objective limit is set and Mosek claims that it is exceeded, check that this is indeed the case in SCIPlpiIsStable()
352- the .mps file reader was extended to additionally accept .mps files with the objective sense section on one line
353- ensure that delayed cutpool separation does not happen if enough cuts have been found already
354- fixed that a Gurobi or Mosek interface (LPI) could not be freed from a thread different than the one it was created in, which lead to problems when, e.g., using the concurrent optimizer
355- in cons_varbound if both variables are fixed, instead of propagating the constraint check the feasibility of the constraint since propagating can lead to unnecessary numerical troubles
356- fixed memory leak in branching rule "distribution"
357- fixed that undercover did not enforce that sufficiently many variables in an and-constraints were fixed to have it linearized in the generated sub-scip
358- fixed two bugs in cons_varbound: avoid adding variable bounds if vbdcoef is infinite and unlock/lock variables if lhs/rhs/vbdcoef are changed
359- globalize constraint changes before bound changes during the effective root shift in treeSwitchPath() to correctly update variable locks by avoiding global bounds with outstanding bound change events when deleting constraints
360- fixed error when attempting to copy SCIP with activated pricers
361- remove integrality check for implicit integral variables in cons_integral.c, updated the definition for variable type implicit integer to be more explicit that these variables can take fractional values, and updated FAQ entry
362- updated and, or, and pseudoboolean constraint handlers to better handle fractional implicit integer variables in enforcement
363- avoid invalid strong Chvatal-Gomory cuts by ceiling with tolerance in the calculation of parameter k and flooring slack coefficients with standard epsilon tolerance as well as quad precision
364- add missing row links to columns in SCIPflushRowExtensions() required to maintain correct row norms
365- restrict separator intobj to solutions for which there can be no better feasible integral objective values to avoid cutting them off
366- delay removal of clique lists from SCIPvarRemoveCliquesImplicsVbs() into cliqueCleanup() to avoid segmentation faults by incomplete cleanups after variable conversions
367- reject sub-solutions with invalid objectives in SCIPtranslateSubSols() due to contradicting infinite contributions
368- correct column index in getMinMaxActivityResiduals() to make presolver dualinfer work
369- copy quiet flag from main scip's message handler to the one of solverscip in concurrent optimization
370- avoid bound tightening cycles towards huge redundancy bounds in fullDualPresolve() to avert fatal numerical trouble in representing vertices of linear relaxations with unbounded domains
371- fix problem where debug solution did not work if branching constraints are present
372- update index of dominating variable on coefficient deletion in dualPresolving() of constraint handler logicor
373- pass on flags from a redundant to the implying varbound constraint in preprocessConstraintPairs() to avoid suboptimal fixings by model relaxations
374- apply reductions of dualinfer only if a dual solution exists (primal is bounded)
375- before presolving is finished check solutions before retransforming them including tiny values to keep check flags consistent
376- disable heuristics before and during presolving in benders decomposition to avoid messing up the objective structure in the solution store by dropping auxiliary variables in the required retransformations
377- correct local flag of singleton conflict constraints in tightenSingleVar() against invalid bound globalization
378- respect unboundedness in the computation of activity bounds in conflict.c to avoid invalid huge bounds due to small coefficients on unbounded variables
379- ensure positive sides of a linear constraint when recognizing a set partition in rangedRowSimplify() to account for redundancy issues
380- relax numerical conditions for variable aggregations to avert invalid variable fixings
381- fixed harmless read of uninitialized data when creating parameters
382- fix call of SCIPnlpiOraclePrintProblem in nlpi_worhp
383
384Performance improvements
385------------------------
386
387- Use sassy/bliss as default symmetry computation package.
388
389Interface changes
390-----------------
391
392### Interfaces to external software
393
394- added interface to nauty/traces for symmetry computation
395- added interface to sassy, a preprocessor for symmetry computation
396- The directory src/sassy contains the source code of sassy.
397
398Build system
399------------
400
401### Cmake
402
403- added flag option "SYM=sbliss" for using sassy/bliss as a graph automorphism package
404
405### Makefile
406
407- added flag option "nauty" for SYM variable to specify which graph automorphism package should be used
408- added flag option "sbliss" for SYM variable to specify which graph automorphism package should be used
409- use SYM=sbliss by default, since sassy and bliss are now shipped with SCIP
410
411Miscellaneous
412-------------
413
414- the parameter change callback is no longer called at the moment a parameter is created
415
416@page RN80 Release notes for SCIP 8.0
417
418@section RN804 SCIP 8.0.4
419*************************
420
421Features
422--------
423
424- use quad precision in cutsSubstituteMIR() for substituting slack variables into CMIR cuts
425- use quad precision for activity computations in cons_linear.c
426
427### Deleted and changed API methods
428
429- SCIPshrinkDisjunctiveVarSet() no longer attempts to cutoff the current node if it finds the
430 given disjunction to be infeasible; it is now in the responsibility of the caller to act accordingly
431
432### New API functions
433
434- added SCIPskipSpace
435- added XML parser routines from src/xml/xml.h
436
437### Interfaces to external software
438
439- updated XPRESS interface to work with XPRESS 41 as well
440- new interface to LP solver HiGHS (lpi_highs.cpp)
441
442### Changed parameters
443
444- changed integer parameter "propagating/symmetry/recomputrestart" from range {0, 1, 2} to being fixed at value 0
445
446Unit tests
447----------
448
449- added new checks for objective, bounds and sides inside the scaling tests in lpi/change.c
450
451Fixed bugs
452----------
453
454- relax condition of assert in lpSolve to hold only if lp/checkstability is true
455- OPB reader: dynamically increase the size of the line buffer for reading in getMaxAndConsDim()
456- Enabled the solution limit checks in SCIPsolveIsStopped in solve.c when in SCIP_STAGE_PRESOLVING
457- fix quad precision comparison for the calculation of knapsackcover constraints.
458- force copying of symmetry constraints for concurrent solve
459- increase the precision of double multiplications in quad precision environments
460- corrected handling of different variable types in symmetry
461- orbitope detection: refine computation of overlap structure and fixed bug in finding orbitope generators
462- ensure that winner is always determined in concurrent mode
463- when a row with invalid index range is added to the global cutpool, update the indices instead of failing with an assert
464- update of watched literals in cons_xor.c and ensure that fixed variables are counted in propacateCons()
465- avoid some numerical issue in check for redundant variables in linear constraints (introduced with version 8.0.2)
466- more rows are treated as being integral in cutsSubstituteMIR() for CMIR cuts
467- fixed several relaxations of the rhs of cuts to 0 in cuts.c
468- avoid aggregation into a single linear constraint if they should not be upgraded (needed for indicator constraints)
469- apply effective root changes before fork is repropagated during treeSwitchPath() in tree.c
470- avoid invalid objective value for solutions generated from an unbounded LP relaxation in case of a nonlinear objective function
471- disable recomputing symmetries after a restart (constraint removal is not permitted)
472- avoid cutting off optimal solutions for small feasibility tolerances in conflict analysis
473- initialize variable in presol_dualsparsify.c
474- fix in presolving of variable bound constraints to use absolute instead of relative difference
475- free variable histories in reoptimization mode
476- handle whitespaces in interactive shell history consistently
477- check and enforce equalities on which the objective is projected in cons_linear.c
478- ensure row feasibilities of solution shiftings in heur_oneopt.c and heur_twoopt.c
565- new parameters to turn on more statistics: misc/showdivingstats (diving heuristics), heuristics/alns/shownbstats (ALNS), estimation/showstats (tree size estimation)
566
567### Data structures
568
569- added nrootcalls and ncutsadded to SCIP_Cutpool
570- added fromcutpool flag to SCIP_Row and fixed 33 bit allocation
721 Removed support for parameterized expressions.
722- Added support for expression types sin, cos, and entropy. Added an expression type that stores a SCIP variable.
723- Added handling of sin and cos expressions in OSiL reader.
724- Added handling of sin, cos, and tan expressions in ZIMPL reader.
725- Added expression handler plugin type, removed user expression type.
726- Replaced expressions, expression trees, and expression graphs by a new implementation of expressions.
727- Added differentiation methods (Gradients and Hessian directions) to expressions.
728- Added integrality information to expressions.
729- Added comparison and hashing of expressions.
730- Improved simplification of expressions and identification of common subexpressions, in particular terms that appear
731 equally in several quadratic functions are now identified.
732- Expression simplification now expands powers also when the resulting exponents will be larger than 2.
733- Added table to print statistics on expression handlers.
734- Removed interval-arithmetic evaluation from expression interpreter (interfaces to automatic differentiation codes).
735- Hessians for user-provided expression handlers are not available in the NLP solver interfaces for now.
736- Sparse Hessians are now returned by expression interpreter. Removed dense Hessians.
737
738Constraint handlers for NLP:
739- cons_nonlinear has been completely rewritten and now handles constraints of the form lhs <= expr <= rhs, where
740 expr is an expression using the new expression type. A linear part of a nonlinear constraint is no longer distinguished.
741- Methods that work on a particular nonlinear structure are now implemented via nonlinear handlers (nlhdlr).
742 These handlers are plugins of cons_nonlinear and interact with cons_nonlinear by detecting structures in expressions and
743 providing propagation and separation mechanisms.
744- Added nlhdlr "default" as a mandatory nlhdlr: this is a nlhdlr that gets active on expressions that no other nlhdlr handles.
745 It then uses the callbacks implemented in expression handlers to provide domain propagation and linear under/overestimates.
746- Added nlhdlr for quadratic expressions: domain propagation that was previously part of cons_quadratic; separation via intersection cuts (currently disabled).
747- Added nlhdlr for bilinear expressions: collects bilinear products and provides under/overestimation of a product over a 2D-projection of the LP.
748- Added nlhdlr for convex and concave expressions: detection of convex/concave subexpressions and linear under/overestimation.
749- Added nlhdlr for quotients: detects quotients, provides specialized linear under/overestimation and domain propagation for univariate quotients.
750- Added nlhdlr for perspective reformulations: detects expressions in semi-continuous variables and tightens linear
751 under/overestimates of these expressions by applying a perspective transformation.
752- Added nlhdlr for second-order cones: detects second-order cone constraints (as ||x|| <= t or a quadratic that can written like that) and
753 separates on a disaggregated reformulation (similar to cons_soc previously).
754- Removed constraint handlers abspower, bivariate, quadratic, and soc.
755- Removed simplification of duplicate abspower constraints for now.
756 Removed simplification of abspower constraints with loose variables.
757 Removed resolving of domain propagation (ConsResProp callback) and conflict analysis for abspower constraints.
758 Removed propagation of varbounds for variables of abspower constraints.
759 Removed reformulation of abs(x)^p * x into signpower expression for now.
760- Removed reformulation of SOC constraints when adding to the NLP.
761 Removed possibility to add linearizations a la Glineur or BenTal&Nemirovski for SOC constraints.
762- Removed possibility to disaggregate quadratic constraints.
763 Removed lifted tangent inequalities for bilinear terms in quadratic constraints.
764 Removed option to project LP solution onto feasible region of a quadratic constraint via interior point or gauge function.
765 Removed handling of unbounded LPs when enforcing quadratic constraints.
766- Removed construction of cuts from interval gradients for nonlinear constraints.
767 Removed possibility to pretend that all nonlinear constraints are convex.
768 Removed possibility to create local or non-initial nonlinear constraints for now.
769- Removed explicit reformulation of nonlinear constraints in presolve.
770 An extended formulation is now generated implicitly and used to construct the LP relaxation,
771 but the original formulation is used to check feasibility, propagate variable domains, etc.
772 Variables that are added for the extended formulation are now marked as relaxation-only.
773- Improved locking of nonlinear variables in nonlinear constraints by taking monotonicity into account.
774- Improved mechanisms to detect and handle structures in nonlinear constraints, which allows for several algorithms
775 to work simultaneously on equal or overlapping expressions.
776- Improved linearization of (sums of) products of binary variables, e.g., clique information is now taken into account.
777 Removed option to linearize products between a binary and a non-binary variable.
778- Nonlinear constraints with the same function (but possibly different left- or right-hand-side) are now merged.
779- When a variable appears in only one concave less-or-equal constraint, it will be fixed to one of its bounds in more cases now.
780- New branching rule for variables in nonlinear constraints (implemented in cons_nonlinear) that scores candidates
781 based on constraint violation, variable type, and pseudo-costs simultaneously.
782- Added tables to print statistics of nonlinear constraint handler and nonlinear handlers.
783
784Performance improvements
785------------------------
786
787- Use the objective cutoff row as base row for separation in sepa_aggregation.c.
788- Separate lifted cover cuts based on newer lifting function of Letchford and Souli (2019) in sepa_aggregation.c.
789- In-tree restarts due to tree size estimation have been made compatible with orbital fixing.
790- Improved upgrade of orbisacks to packing/partitioning orbitopes.
791- Improved running time of symresack cover separation.
792- Improved propagation algorithm for orbisack and symresack.
793- Improved handling for expressions of type signpower in CppAD interface by making use of CppADs conditional expressions.
794- Faster reevaluation of Hessian for quadratic expressions in CppAD interface.
795- Enabled optimization of taped expressions in the CppAD interface.
796- Sparse Hessian evaluation for expressions with sparse Hessian in the CppAD interface.
797- Disabled branching on variables that are added for the extended formulation of a nonlinear constraint.
798- Prefer branching on variables in nonconvex terms of nonlinear constraints also if a cut could be generated but would yield a small reduction in the convexification gap only.
799- When violations of nonlinear constraints are tiny, the feasibility tolerance for the LP relaxation may now be reduced temporarily to allow for cuts to have an effect.
800- Improved under/overestimation of multidimensional vertex-polyhedral (e.g., multilinear or concave) functions by use of scaling and keeping the cut-generating LP around.
801- Products in nonlinear constraints are no longer disaggregated for the extended formulation.
802- No longer relax bounds of integral variables when computing bounds on activity in nonlinear constraints.
803- Revised and improved Ipopt interface.
804- Revised and improved subNLP primal heuristic, in particular choice of iteration limit and starting condition and reuse of subSCIP.
805- Merge strongcg into the gomory separator to avoid computing the same base equality twice. The files
806 sepa_strongcg.{h|c} have been removed.
807- The RENS neighborhood in ALNS now fixes fractional variables if necessary for reaching its target fixing rate.
808- Use cpsolver emphasis in sepa_rapidlearning.
809- If decomposition/maxgraphedge = 0, the computation of the block graph is completely turned off.
810- Fixed a performance bug in cons_integral.c where rounding information was passed incorrectly to the generic diving algorithm.
811
812Examples and applications
813-------------------------
814
815- Add c++ Sudoku example
816- Removed circle.c and renamed string.c to spring.c in CallableLibrary example.
817- SCIP-Jack (Steiner tree application):
818 Most files have been modified and many new ones have been added (code base more than doubled).
819 Two new problem classes are supported: maximum-weight connected subgraph problem with budget constraints, partial-terminal node-weighted Steiner tree problem.
820 Major performance improvements accross all problem classes that are supported.
821
822Interface changes
823-----------------
824
825### New and changed callbacks
826
827- extend SEPAEXEC{LP,SOL} callbacks by parameter "depth", which should be used within separation instead of SCIPgetCurrentDepth()
828- extend SCIPseparateSolCutpool() by parameter "pretendroot", which is passed to SCIPcutpoolSeparate() instead of SCIPtreeGetCurrentDepth(scip->tree) == 0
846- added SCIP_NLPIPROBLEM* problem to SCIP_DECL_NLPIGETSOLVERPOINTER
847
848### Deleted and changed API methods
849
850- When calling SCIPdelVar() in the SCIP_STAGE_PROBLEM stage, it is now documented as the user's responsibility to ensure
851 the variable is not present in any constraints. Otherwise, SCIPsolve() now returns SCIP_INVALIDDATA.
852- removed SCIPselectCuts(), replaced by SCIPselectCutsHybrid() of the hybrid cut selector plugin
853- If SCIPvarMarkRelaxationOnly() is called for a variable, then this now need to happen before the
854 variable is added to the transformed problem (SCIPaddVar()).
855 SCIPvarMarkRelaxationOnly() will automatically call SCIPvarMarkDeletable().
856- SCIPcomputeOrbitsFilterSym() and SCIPcomputeComponentsSym(): Type of argument componentblocked
857 changed from SCIP_Shortbool* to unsigned*.
858- removed SCIPsetParam()
859- SCIPcreateConsOrbitope() and SCIPcreateConsBasicOrbitope() have two new arguments "usedynamicprop"
860 and "mayinteract" to encode whether a dynamic reordering of the orbitope rows shall be used in
861 full orbitope propagation and whether the orbitope might interact with other symmetry handling
862 methods, respectively.
863- internal function SCIPgetPropertiesPerm() has been replaced by SCIPisInvolutionPerm()
864- internal function SCIPgenerateOrbitopeVarsMatrix() has new arguments "storelexorder", "lexorder",
865 "nvarsorder", "maxnvarsorder" to compute and store the lexicographic order defined by an orbitope
866- renamed SCIPcomputeArraysIntersection() and SCIPcomputeArraysSetminus() to
867 SCIPcomputeArraysIntersectionInt() and SCIPcomputeArraysSetminusInt(), respectively, and changed
868 their return type from SCIP_RETCODE (which _always_ was SCIP_OKAY) to void
869- removed SCIPincludeDialogDefault(), use SCIPincludeDialogDefaultBasic() instead and check whether you also need SCIPincludeDialogDefaultSet() and SCIPincludeDialogDefaultFix()
870- removed exprint argument from SCIPaddNlRowGradientBenderscutOpt()
871- added copyexprhdlrs argument to SCIPcopyPlugins() (19th position)
872- added copycutselectors argument to SCIPcopyPlugins() (10th position)
873- removed refpoint argument from SCIPaddSquareSecant()
874- added argument exprdata to SYMcomputeSymmetryGenerators()
889- renamed SCIPsetNlRowExprtree() to SCIPsetNlRowExpr() and changed type of expr(tree) argument to SCIP_EXPR*
890- SCIPenableNLP() is no longer allowed in stages INITSOLVE and SOLVING
891- removed SCIPaddLinearConsToNlpHeurSubNlp()
892- SCIPhasNLPSolution() now returns true also if a infeasible solution to the NLP exists; SCIPcreateNLPSol() can now also be used when only an infeasible solution to the NLP exists
893- renamed SCIPsolveNLP() to SCIPsolveNLPParam() and added parameter SCIP_NLPPARAM param
894- removed SCIPsolveDiveNLP(), use SCIPsolveNLPParam() instead
942- removed SCIPnlpiOracleGetVarDegree() and SCIPnlpiOracleGetVarDegrees(), use SCIPnlpiOracleIsVarNonlinear() and SCIPnlpiOracleGetVarCounts(), respectively, instead
943- removed SCIPnlpiOracleGetConstraintDegree(), use SCIPnlpiOracleIsConstraintNonlinear() instead
944- removed argument messagehdlr from SCIPnlpiOraclePrintProblem() and SCIPnlpiOraclePrintProblemGams()
945- removed SCIPcreateNlpiProb(), use SCIPcreateNlpiProblemFromNlRows() instead
946- renamed SCIPupdateNlpiProb() to SCIPupdateNlpiProblem() and moved into scip_nlpi.{h,c}
947- renamed SCIPaddNlpiProbRows() to SCIPaddNlpiProblemRows() and moved into scip_nlpi.{h,c}
949- removed SCIPgetIpoptApplicationPointerIpopt(), use SCIPgetNlpiSolverPointer() instead
950- removed SCIPnlpStatisticsCreate(), SCIPnlpStatisticsFree(), SCIPnlpStatisticsGetNIterations(), SCIPnlpStatisticsGetTotalTime(), SCIPnlpStatisticsSetNIterations(), SCIPnlpStatisticsSetTotalTime(), the struct is public now
951- renamed LapackDsyev() to SCIPcallLapackDsyevIpopt()
952- renamed SCIPsolveLinearProb() to SCIPsolveLinearEquationsIpopt()
953
954Expression interpreter:
955- removed functions that operated with SCIPInterval
956- changed first argument of SCIPexprintCreate() to SCIP*
957- added SCIP* as first argument to SCIPexprintFree()
958- added SCIP* as first argument to SCIPexprintCompile(), changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA**
959- added arguments SCIP*, SCIP_EXPRINT*, and SCIP_EXPR* as first arguments to SCIPexprintFreeData()
960- renamed SCIPexprintGetExprtreeCapability() to SCIPexprintGetExprCapability();
961 added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
962- removed SCIPexprintNewParametrization()
963- SCIPexprintEval(): added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
964- removed SCIPexprintEvalInt()
965- SCIPexprintGrad(): added SCIP* as first argument, changed third argument to SCIP_EXPR*, added fourth argument SCIP_EXPRINTDATA*
966- removed SCIPexprintGradInt()
967- removed SCIPexprintHessianSparsityDense() and SCIPexprintHessianDense, use SCIPexprintHessianSparsity() and SCIPexprintHessian() instead
968
969Expressions:
970- removed SCIPexpropGetName(), use SCIPexprhdlrGetName() instead
971- removed SCIPexpropGetNChildren()
972- removed SCIPexprGetOperator(), use SCIPexprGetHdlr() instead
973- removed SCIPexprGetOpIndex(), SCIPexprGetOpReal(), SCIPexprGetOpData(), use SCIPexprGetData() instead
974- removed SCIPexprGetRealPowerExponent(), SCIPexprGetIntPowerExponent(), SCIPexprGetSignPowerExponent(), use SCIPgetExponentExprPow() instead
975- removed SCIPexprGetLinearCoefs(), SCIPexprGetLinearConstant(), use SCIPgetCoefsExprSum() and SCIPgetConstantExprSum() instead
1095- renamed SCIPgetNAllBilinearTermsQuadratic() to SCIPgetNBilinTermsNonlinear() and changed argument from SCIP* to SCIP_CONSHDLR*
1096- renamed SCIPgetAllBilinearTermsQuadratic() to SCIPgetBilinTermsNonlinear() and replaced arguments by SCIP_CONSHDLR* and changed return type to SCIP_CONSNONLINEAR_BILINTERM*
1097- removed SCIPaddBilinearIneqQuadratic(), use SCIPinsertBilinearTermImplicitNonlinear() instead
1098- renamed SCIPcreateConsQuadratic() to SCIPcreateConsQuadraticNonlinear() and removed argument stickingatnode
1099- removed SCIPincludeConshdlrSOC()
1100- replaced SCIPcreateConsBasicSOC() by SCIPcreateConsBasicSOCNonlinear()
1101- deprecated SCIPcreateConsSOC(), use SCIPcreateConsBasicSOCNonlinear() instead
1102- deprecated SCIPgetNlRowSOC(), use SCIPgetNlRowNonlinear() instead
1322- Removed parameters for strongcg separator: separating/strongcg/..., i.e.,
1323 maxrounds, maxroundsroot, maxsepacutsroot, maxsepacuts, dynamiccuts. One can control the
1324 strongcg behavior throught the parameters of sepa_gomory.
1325- renamed separating/{minortho,minorthoroot,objparalfac,intsupportfac} to cutselection/hybrid/{minortho,minorthoroot,objparalweight,intsupportweight}
1326
1327### New parameters
1328
1329- It is now possible to add orbitope constraints to handle symmetries even if not all variables
1330 in a component of the symmetry group are binary. This feature can be enabled using the
1389- new parameters "branching/inference/conflictprio" and "branching/inference/cutoffprio" that allow
1390 using the different score criteria in inference branching hierarchically
1391- new parameters "heuristics/alns/nodesquotmin", "heuristics/alns/maxcallssamesol" and "heuristics/alns/initduringroot"
1392 to control neighborhoods in ALNS
1393- new parameter "benders/default/benderscut/optimality/mir" to control whether mixed-integer rounding procedure is applied to Benders optimality cuts
1394- new parameter "misc/avoidmemout" to try to avoid running into memory limit
1510- added test projection:transitivity in prob/obbt.c
1511- added reader/nl.c
1512- added test intervalarith:sincos in scip/intervalarith.c
1513- added sepa/minor.c
1514- added sepa/rlt/cuts.c
1515- added sepa/rlt/product_detection.c
1516- added sepa/rlt/separation.c
1517- added tests test_compute_symmetry:expr{1,2,3,4} in symmetry/compute.c
1518
1519Build system
1520------------
1521
1522- the separate NLPI library has been integrated into the main SCIP library;
1523 uses of NLPILIBFILE or NLPILIBSRC in Makefiles that use make/make.project
1524 should be removed
1525
1526### Cmake
1527
1528- replace flag PARASCIP by THREADSAFE
1529- option AMPL is now ON by default
1530- add -D_XOPEN_SOURCE=600 cflag for compilation on systems other than windows
1531- add compile options directly instead of modifying CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
1532
1533### Makefile
1534
1535- prefix PKG_CONFIG_PATH with Ipopt's pkgconfig dir instead of postfixing
1536- replace flag PARASCIP by THREADSAFE
1537- flag AMPL is now true by default
1538- libscip has been renamed to libscipbase and libscipsolver has been renamed to libscip
1539 in order to have the same library names for makefiles and cmake. For downward
1540 compatibility libscipsolver still exists (as a link).
1541
1542Fixed bugs
1543----------
1544
1545- fixed handling of multi-aggregation in cons_symresack and cons_orbisack
1546- SCIPgetLowerbound() now consistently returns infinity when status is infeasible
1547- improved the likelihood that a solution that satisfies the nonlinear constraints in the transformed (presolved) problem is also feasible for the original problem
1548- worked around a problem with derivatives of pow at 0 with non-integer exponents in CppAD
1549- fixed that setting of feasiblity and optimiality tolerance for NLP relaxation was overwritten with defaults when solving NLP
1550- fixed variance computation in t-value computation in hypothesis testing of reliability branching
1551- fixed potential overflow in cuts.c:evaluateLiftingFunctionKnapsack()
1552- do not transfer dual reductions to main SCIP in sepa_rapidlearning if strong dual reductions are forbidden
1553- fixed a bug in cons_setppc.c:removeDoubleAndSingletonsAndPerformDualpresolve() which led to wrong variable aggregations
1554- added missing redundancy check to coefficient tightening routine in cons_varbound that led to wrong variable locks
1555- added a check of numerics to avoid wrong reductions in cons_linear.c:simplifyInequalities()
1556- fixed a bug in cons_logicor.c regarding fixed variables that were not removed
1557- presol_milp.c handles variable fixings, suggested by PaPILO, more carefully to cover all cases that can appear
1558- fixed several reproducability bugs that led to different solving paths across multiple runs with one SCIP environment
1559- fixed check of limits/absgap, which was incorrectly applied to the scaled objective of the transformed problem
1560
1561Miscellaneous
1562-------------
1563
1564- in LP, use absolute instead of relative tolerances to check whether solutions from LP solver are primal feasible
1565- when a restart occurs, SCIP now asserts (during EXITSOLVE) that all relaxation-only variables are unlocked and
1566 only captured by the transformed problem.
1567- Avoid redundant calls to LP solver when LP is already flushed and solved
1568- In SCIPdebugMsg(), SCIPsetDebugMsg(), SCIPstatDebugMsg() strip directory from filename.
1569- Recompute activity of rows when checking LP solutions instead of trusting the value given by the LP solver
1570- The define NPARASCIP has been replaced by SCIP_THREADSAFE
1571- Parameters are not reset to their default values before activating an emphasis setting; this now allows to combine
1572 different emphasis settings.
1573- If a lazy bound is set to a value that is tighter than the current global bound, then the global bound is now tightened accordingly.
1574
1575@page RN70 Release notes for SCIP 7.0
1576
1577@section RN703 SCIP 7.0.3
1578*************************
1579
1580Interface changes
1581-----------------
1582
1583### New API functions
1584
1585- added function SCIPwithDebugSol() to determine whether SCIP was compiled with WITH_DEBUG_SOLUTION
1586
1587- New function SCIPcreateConsBounddisjunctionRedundant() and SCIPcreateConsBasicBounddisjunctionRedundant() that allow
1588 the input to contain redundant literals.
1589
1590### Changed API functions
1591
1592- added __attribute__((format(printf,,,))) to variadic SCIP message printing functions;
1593 this enables warnings about mismatches between format string and variadic function arguments if using GCC.
1594
1595### Interfaces to external software
1596
1597- removed MATLAB interface from interfaces/matlab
1598
1599Build system
1600------------
1601
1602- Compilation will now also work in a raw tarball of the scip git repository
1603
1604### Cmake
1605
1606- Make find_package more verbose and require packages to be found. Now enabled packages that are not found result in an error.
1607
1608Fixed bugs
1609----------
1610
1611- Fixed numerical bug by creating and checking the empty solution when problem vanishes in presolving.
1612- Fixed several bugs in reoptimization.
1613- Fixed bug in cons_bounddisjunction in which a constraint leads to a cutoff.
1614- Fixed bug in reoptimization by avoiding redundant literals for bound disjunctions.
1615- Replace wrong usage of CMAKE_BINARY_DIR by PROJECT_BINARY_DIR in CMake system
1616- Fixed lpi_glop to use absl flag instead of GFlags
1617- Fixed invalid initialization of limits/softtime parameter in cons_components
1618- Fixed MIN macro not defined in some cases.
1619- Safeguard some API methods for querying solving statistics against segmentation faults after SCIPpresolve()
1620- Fixed unfreed solution in concurrent solving
1621- Make sure that logicor constraints are enforced/separated if genlogicor is true in cons_indicator.
1622 Thus, do not change constraints/logicor/sepafreq anymore, but output warning.
1623- Fixed assert that assumed infeasibility cannot occur in presol_boundshift.
1624- Fixed sign bug during creation of conflict constraints with almost zero left-hand side.
1625- Disabled call of conflict handler for conflict sets that contain relaxation-only variables.
1626- Fixed bug in cons_symresack by initializing all constraint data in constrans
1627- Avoid allowing the upgrade of linear constraints corresponding to indicators in propagation of nodes.
1628- Fixed bug in computing lex. min/max faces in dynamic orbitope propagation.
1629- Limit vbounds propagator to one sweep through all bounds per call in order to avoid an infinite loop.
1630- Fixed mismatches between formatter strings and arguments in calls to SCIP message printing functions.
1631
1632Miscellaneous
1633-------------
1634
1635- To avoid performance variablity during reoptimization, the active constraints are now stored in the same order as in the
1636 original problem.
1637- Added workaround for bug in MSVS 2019 when compiling CppAD source.
1638- The original order of variables is now only restored after presolve if `randomization/permutevars` is set to FALSE.
1639
1640@section RN702 SCIP 7.0.2
1641*************************
1642
1643Features
1644--------
1645
1646- Extended check for valid variable and constraint names in PIP writer.
1647- Indicator constraints now write the name of the linear constraint in CIP format. This avoids a complicated
1648 name matching during parsing. The old format is still supported.
1649- The objective scale and offset are now taken into account when reading/writing problems in lp/mps/fzn/pip format.
1650 This often changes the behavior when writing transformed problems.
1651
1652Performance improvements
1653------------------------
1654
1655Examples and applications
1656-------------------------
1657
1658- Add c++ Sudoku example
1659
1660Interface changes
1661-----------------
1662
1663### Deleted and changed API methods
1664
1665- deprecated SCIPsetParam(); use SCIPsetIntParam(), SCIPsetRealParam(), etc, instead
1666
1667### New API functions
1668
1669- new function SCIPcolGetVarProbindex() for accessing the probindex of a variable corresponding to a column
1670- added new sorting functions SCIPsortPtrRealRealBoolBool()
1671
1672Fixed bugs
1673----------
1674
1675- Fixed a sign bug occuring for some cases in the computation of the directed cutoff distance
1676- Fixed overflow in inference information of cumulative constraint handler
1677- Fixed problem with propfreq == 0 in cons_linear.c
1678- Fixed aggregation heuristic in sepa_aggregation.c to not use local rows when that is requested nor modifiable rows
1679- Fixed problem with incompatibility of symmetry handling in Benders decomposition
1680- Fixed parsing of small number in CIP format of nonlinear constraint
1681- Fixed problem in upgrading full orbitopes to partitioning orbitopes
1682- Fixed treatment of negated variables in parsing orbitope constraints
1683- Fixed potential indexing error in prop_vbounds.c
1684- Fixed bug in writing fzn format
1685- Revert to old parameter value when parameter change is rejected in PARAMCHGD callback
1686- Fixed order of linker flags when building AMPL interface with cmake system.
1687- Fixed bug with ofsymcomptiming == 0: now symmetry is actually computed
1688- Improved separation for SOC constraint with multiaggregated variable on right-hand-side.
1689- Fixed bug in presol_boundshift: do not shift non-active variables
1690- Fixed bug in domain propagation for SOC constraints with negative coefficient for variable on right-hand-side.
1691- Fixed bug with multi-aggregated integer variables in cons_xor.
1692- Fixed bug with changed number of variables in storing relaxation solution in probing/diving.
1693- Fixed issues with scip statistics
1694- Fixed issue with multi-aggregated variables
1695- Fixed issue in with buffer memory in cons_cumulative
1696
1697@section RN701 SCIP 7.0.1
1698*************************
1699
1700Build system
1701------------
1702
1703### Cmake
1704
1705- Fixed cmake module for Ipopt to support Ipopt 3.13
1706- Added cmake variable BLISS_LIBRARY_DIR to pass a bliss library
1707- Added warning to require minimal GCC version 4.8
1708- Renamed FindCriterion cmake findmodule to FindCRITERION
1709
1710### Makefile
1711
1712- Updated make/make.project for macOS
1713- Add SANITZERFLAGS (only OPT=dbg) to LDFLAGS also if SHARED=true (and rename SANITZERFLAGS to SANITIZERFLAGS)
1714- Fixed GCC version check in make/make.linux.gnu.dbg
1715
1716Fixed bugs
1717----------
1718
1719- Fixed handling of constant term in quadratic objective of pip-reader
1720- Fixed incorrect value string for parameter estimation/completiontype
1721- Fixed initialization of first LP which led to wrong output about LPs not resolved correctly
1722- Fixed bug in SCIPcutpoolClear() function not clearing internal datastructures properly
1723- Fixed inability to set a value in a solution if it was within epsilon to the current value
1724- Fixed problems for linking optimized code with debug library of SCIP (and vice versa) by moving debug-only members
1725 to end of SCIP structs
1726
1727Miscellaneous
1728-------------
1729
1730- Variables that are marked as relaxation-only are no longer checked against debug solutions if
1731 they are captured by the transformed problem only.
1732
1733@section RN700 SCIP 7.0.0
1734*************************
1735
1736Features
1737--------
1738
1739- Using the parameter "propagating/symmetry/recomputerestart" one can now decide to recompute symmetries after a
1740 restart or not. Previously one could just turn off symmetry computation after a restart. If orbital fixing
1741 has found a reduction before the restart occured, symmetries have to be updated to ensure correctness.
1742 To this end, the user can decide via "propagating/symmetry/disableofrestart" whether orbital fixing is disabled or
1743 whether symmetries are recomputed.
1744
1745- extended relaxators statistics in solve statistics about information on number of cutoffs, improved bounds, etc.
1746
1747- extends SMPS file reader for the stochastic information, the sto files, to read a lower bound for the discrete
1748 scenarios. The lower bound is used when creating the auxiliary variables for Benders' decomposition.
1749
1750- extended Benders framework to solve NLPs and generate optimality and feasibility cuts from their solution
1751 when the subproblem is convex nonlinear.
1752
1753- extended Benders framework to create copies of Benders decompositions that can be used in a multithreading environment
1754
1755- additional functionality has been added to enable the transfer of Benders' decomposition cuts between different SCIP
1756 instances, e.g., when used in UG
1757
1758- LP rows (SCIP_ROW) can now store pointer to a constraint from which the row originates
1759
1760- Trust region, a new LNS heuristic, has been added to SCIP as both a standalone primal heuristic heur_trustregion.c
1761 and as a neighborhood inside of Adaptive Large Neighborhood Search (heur_alns.c). This heuristic is designed to improve the
1762 heuristic performance of the Benders' decomposition algorithm. It builds upon the successful trust region approaches
1763 applied to Benders' decomposition.
1764
1765- Modularity of symmetry handling has been increased. It is now possible to use orbitopes (i.e., polyhedral symmetry
1766 handling techniques) and orbital fixing on the same instance.
1767
1768- cut strengthening enabled within the Benders' decomposition framework. This uses a mix of the Improved Magnanti-Wong
1769 method and Kelly's method. The cut strengthening is enabled by setting the paramemter
1770 "benders/<bendersname>/cutstrengthenenabled" to TRUE. The parameters "cutstrengthenmult", "noimprovelimit" and
1771 "corepointperturb" control the behavior of the cut strengthening method. Additionally, the parameter
1772 "cutstrengthenintpoint" allows the user to specify the solution that is used to initialize the core point. The options
1773 are the first LP solution, the first integer feasible solution, a relative interior point, a solution vector of all
1774 ones and a solution vector of all zeros. Also, the core point can be reinitialized after each update to the incumbent
1775 solution.
1776
1777- added option to adjust weights of different scores in relpscost (hybrid) branching rule based on degeneracy information
1778 and skip strong branching for very high degeneracy rates
1779
1780- added new SCIP_DECOMP* object to store user decompositions. The user can specify one or several decompositions by assigning variable
1781 and/or constraint labels either through the API or by reading a file in DEC format (which is one of the formats that GCG writes).
1782 This format specifies constraint labels, variable labels are inferred from that. The decomposition is transformed after presolving.
1783- statistics regarding the number of blocks, the largest and smallest blocks, the border, and the constraint graph are printed for the original decomposition,
1784 and for each decomposition after presolving.
1785- the decomposition can be used as initial decomposition for the Benders functionality of SCIP.
1786- new subsection "How to provide a problem decomposition" in the SCIP documentation
1787
1788- GINS heuristic can make use of a user-provided decomposition labels in two ways:
1789 1. by selecting a block of variables that maximizes the potential, and randomly selecting a start variable for the neighborhood and/or
1790 2. by selecting an interval of consecutive blocks as neighborhood, until fixing rate is reached. In this case, no variable is randomly selected.
1791
1792- extend potential parameter of GINS to allow computation based on local LP solution, as well
1793
1794- new primal heuristic Adaptive Diving, which registers all publicly available dive sets from other diving heuristics.
1795 At each call, it selects one of the available dive sets based on the user's score type choice (heuristics/adaptivediving/scoretype).
1796 During the solution process, the heuristics learns online which divesets reach the best score, and executes them more frequently.
1797 The statistic output for Diving heuristics has been extended to incorporate the statistics of each dive set within Adaptive diving.
1798
1799- Added new penalty alternating direction method (PADM) primal heuristic that splits the problem into several sub-SCIPs
1800 according to a user-provided decomposition. The sub-SCIPs are solved on an alternating basis until a feasible solution of
1801 the original problem is found.
1802
1803- Symmetry handling constraints (cons_orbisack, cons_orbitope, cons_symresack) now have an additional parameter to encode
1804 whether they are model constraints, i.e., define the problem, or whether they are only present to handle symmetries.
1805
1806- The symmetry code has been completely restructured. The presolvers presol_symbreak and presol_symmetry as well as the propagator
1807 prop_orbitalfixing have been merged into the single propagator prop_symmetry to avoid storing the same information
1808 multiple times. This propagator is now responsible for adding symmetry handling constraints as well as activating orbital
1809 fixing. Moreover, the new file symmetry.c contains general functions for symmetry computations like orbit computations.
1810
1811- Variables can now be marked as "relaxation-only". This flag should be used to introduce new variables that are required
1812 to define a relaxation, but that are not part of any checked constraints. Essentially, these variables should only be used
1813 in the current SCIP solve and disregarded after a restart or in SCIP copies. Hence, these variables are not copied by SCIPcopy and
1814 SCIPgetVarCopy, they are currently not used in conflict constraints, and cuts involving them are not upgraded to linear constraints.
1815 Relaxation-only variables cannot appear in the objective function.
1816
1817- The OSiL reader now supports nonlinear expressions of type "signpower".
1818
1819- Expressions of form abs(x)^p * x in a nonlinear constraint are now sometimes recognized and handled by abspower constraints.
1820
1821- If polyhedral symmetry handling methods are used (cons_orbisack, cons_orbitope, cons_symresack), it is now possible to
1822 recompute symmetries if a restart occured.
1823
1824- upgrade some more quadratic constraints to second-order cone constraints, that is,
1825 handle linear binary variables as if squared in simple upgrade and
1826 do not require bounds for variables that have a zero entry in the computed eigenvectors in the non-simple upgrade
1827
1828- new variable event when changing the variable type
1829
1830- It is no longer necessary to provide a SCIP pointer for the subproblem in SCIPaddBendersSubproblem if custom solving
1831 methods are defined. A NULL pointer can be supplied to SCIPaddBendersSubproblem. In this case, no internal Benders'
1832 cut generation methods can be used.
1833
1834- Using the parameter "constraints/symresack/checkmonotonicity" one can now decide to upgrade to packing/partitioning
1835 symresacks even if the underlying permutation is not monotone.
1836
1837- New branching rule `vanillafullstrong`, mostly for scientific purpose, with the following features:
1838 1) no cutoff or domain reduction: only branching;
1839 2) idempotent (optional): leave SCIP, as much as possible, in the same state before / after the strong branching calls
1840 - basically, do not update any statistic;
1841 3) donotbranch (optional): do no perform branching. So that the brancher can be called as an oracle only
1842 (on which variable would you branch ? But do not branch please);
1843 4) scoreall (optional): keep scoring variables, even if infeasibility is detected;
1844 5) collectscores (optional): store the candidate scores from the last call, which can then be retrieved by calling SCIPgetVanillafullstrongData();
1845 6) integralcands (optional): consider integral candidates for branching,
1846 i.e., get candidates from SCIPgetPseudoBranchCands() instead of SCIPgetLPBranchCands().
1847
1848- If a reference value (misc/referencevalue) is given, the primal-reference and reference-dual integrals are calculated automatically and printed within the SCIP statistics.
1849
1850- Locally valid cuts / rows are now considered for dual proof analysis when `conflict/uselocalrows` is set to TRUE.
1851
1852- Linking variables in the linking constraint handler (cons_linking.{ch}) can now be integer or continuous. The coefficients of the binary variables are therefore now stored as SCIP_Real.
1853
1854- To save memory, it is now possible to remove all variables from the internal symmetry data structures that are
1855 not affected by any symmetry.
1856
1857- Allow to filter first variables from orbits and transfer pseudo cost information to variables in orbit
1858
1859- Add integration of external MILP presolve library as a SCIP presolver plugin that runs on MILP problems
1860
1861- Parallelisation can be used when applying Benders' decomposition. There are two different forms of parallelisation
1862 available. The first is applying Benders' decomposition within a parallel branch-and-bound. This is achieved through
1863 the integration with the UG framework. The second is the use of shared memory parallelisation for solving the Benders'
1864 decomposition subproblems. A priority queue has been added to help with load balancing.
1865
1866- The Benders' decomposition framework can handle MINLPs. If a convex relaxation of the MINLP exists, then this is
1867 solved to generate optimality and feasibility cuts. The extensions to the framework are:
1868 - New generic solving methods to solve convex NLP subproblems.
1869 - Modification to benderscut_opt and benderscut_feas to enable the generation of cuts from convex NLPs.
1870 - Addition of benderscut_feasalt to generate feasibility cuts from an alternative subproblem that minimises the
1871 violation of infeasible problems.
1872 - Better handling of subproblem solution results
1873
1874- Adds a feasibility phase to the Benders' decomposition subproblem solving methods. The feasibility phase adds slack
1875 variables to each of the constraints to ensure feasibility of the subproblem. A large coefficient is given to these
1876 slack variables in the objective function to penalise constraint violations. The coefficients are progressively
1877 increased until all slack variables take the value 0.0.
1878
1879- Improved convexity check for Benders' decomposition subproblems. The constraints of the subproblem are now checked for
1880 convexity in the initialisation of the Benders' decomposition algorithm. This enables the solving of convex NLPs as
1881 Benders' decomposition subproblems.
1882
1883- Benders' decomposition can be applied using decomposition supplied in the DEC format. To apply Benders' decomposition
1884 the parameters decomposition/benderslabels and decomposition/applybenders must be set to TRUE.
1885
1886- new event handler event_estim.c/h that approximates search tree completion and estimates tree size
1887 to trigger restarts; many approximations of search tree completion and estimation, including WBE, SSG, and tree profile method
1888- new display column that reports approx. search tree completion during the search, and an overview in the statistics table
1889- added resources (script, tutorial, test data) to adapt tree size estimation to user instances.
1890
1891- Orbital Fixing uses a list of variables that have been fixed globally since the computation of symmetries to filter
1892 symmetries. Previously, some plugins were disabled, which is not necessary anymore.
1893
1894- A new presolver "dualsparsify" was added. It tries to combine columns (i.e. variables) to cancel nonzero coefficients in the constraint matrix.
1895
1896- The presolver "tworowbnd" was implemented with better performance.
1897
1898- To be able to calculate better bounds for the dual variables, the presolver "dualinfer" was extended by the ability to perform convex combinations of continuous columns.
1899
1900- allow disabling of pricers during solving process
1901
1902- added emphasis setting for numerically challenging instances
1903
1904Performance improvements
1905------------------------
1906
1907- Extended cut presolving by removing variables that been fixed at their bounds
1908
1909- Improved branching point selection when branching on externals branching candidates. Instead of using exactly the
1910 LP solution, a point closer to the middle of the variables domain is chosen.
1911
1912- Matrix presolvers that do not work on incomplete matrices now skip matrix creation if unsupported constraint types are detected.
1913
1914- consLockBenders callback implemented to add down locks on the Benders' decomposition auxiliary variables and
1915 up and down locks per subproblem for all master problem variables. This allows the use of presolving and propagation
1916 with Benders' decomposition.
1917
1918- improved performance of orbital fixing in several ways:
1919 store permutations in transposed form to improve cache efficency;
1920 reverse order to speed up filtering of permutations;
1921 handle variables globally fixed to 1 in list;
1922 use event handler to catch global fixings;
1923 speed up orbit computations;
1924 change handling of restarts;
1925 use only permutations that can contribute to a variable's orbit;
1926
1927- allow rapid learning at local nodes
1928
1929- allow to recompute cut without using fractional values for sepa_cgmip
1930
1931- restrict the number of the clique table nonzeros relative to the number of problem nonzeros, which could be a performance bottleneck.
1932
1933- variable fixings of LP face heuristic are now computed earlier; subproblem creation is skipped if not enough variables are fixed.
1934
1935- Improved domcol presolver to not require a complete representation of all constraints in the matrix
1936
1937- performance improvement of adaptive large neighborhood search heuristic on merely continuous problems. The heuristic
1938 stops if presolving in the sub-SCIP fixes less than 50 % of the current target fixing rate over all variables
1939 (including continuous).
1940
1941- reduce memory usage in symmetry detection by a staggered allocation with decreasing overhead for larger instances
1942
1943- improved full orbitope propagation using a static implementation or a dynamic reordering of orbitope rows by a global rank function
1944
1945- improved detection of packing/partitioning orbitopes
1946
1947- enable an in-tree restart if after a reasonable initialization, the estimated size of the remaining tree is large.
1948
1949
1950Examples and applications
1951-------------------------
1952
1953- added methods to set and get hmin and hmax for optcumulative constraints
1954
1955Interface changes
1956-----------------
1957
1958### New and changed callbacks
1959
1960- new optional callback `SCIP_DECL_DIVESETAVAILABLE` to check preconditions for this dive set, e.g., if an incumbent solution is available,
1961 which is passed as new argument to SCIPcreateDiveset(). SCIPcreateDiveset() has another new parameter "ispublic".
1962
1963- new callback `SCIP_DECL_CONSHDLRCOPY` and `SCIP_DECL_CONSCOPY` in cons_orbisack and cons_symresack
1964
1965- new `idempotent` argument to SCIPgetVarStrongbranchInt() and SCIPgetVarStrongbranchFrac(),
1966 so that statistics are not updated during the call. Likewise, new `updatecol` and `updatestat` arguments to SCIPcolGetStrongbranch().
1967
1968- callback `SCIP_DECL_CONSHDLRENFOLP` can now also return SCIP_SOLVELP as *result, which indicates to the SCIP core that the LP relaxation
1969 should be solved again because the primal feasibility tolerance of the LP has been tightened (using SCIPsetLPFeastol())
1970
1971- extension of SCIP_PQUEUE by a new callback SCIP_DECL_PQUEUEELEMCHGPOS to catch swaps as well as functionality to delete arbitrary elements from the priority queue.
1972
1973### Deleted and changed API methods
1974
1975- LPI:
1976 + now for all lp interfaces consistent requirements on SCIP_LPPAR:
1977 LPITLIM and BARRIERCONVTOL positive or zero; FEASTOL, DUALFEASTOL, LPTILIM strictly positive
1978 + now projecting SCIP_LPPAR values on feasible values for each lp interface
1979 + add interface to Glop
1980 + fixed mapping between scaling parameter values in Gurobi LPI lpi_grb
1981- Symmetry:
1982 + removed method SCIPseparateCoversOrbisack() in cons_orbisack.h since the orbitope constraint
1983 handler has its own implementation of this routine with advanced features now
1984 + renamed SCIPgetGeneratorsSymmetry() to SCIPgetSymmetry() and removed two arguments
1985 + extended method SCIPgetSymmetry(): It is possible to access both the original and
1986 transposed permutations matrix as well as the (independent symmetry) components of a permutation group now.
1987 + arguments of functions SCIPcreateConsOrbisack(), SCIPcreateConsBasicOrbisack(), SCIPcreateConsOrbitope(),
1988 SCIPcreateConsBasicOrbitope(), SCIPcreateConsSymresack(), SCIPcreateConsBasicSymresack(), and SCIPcreateSymbreakCons() extended
1989 by "ismodelcons" to encode whether the constraints are model constraints or not
1990 + the function SCIPgetSymmetry() no longer accepts the parameter recompute, but has parameter permvarmap as new input
1994 + add function SCIPcomputeOrbitsComponentsSym() to compute orbits without filtering permutations and indices of orbits for each variable
1995- SCIPallowObjProp() and SCIPallowDualReds() are deprecated and replaced by SCIPallowWeakDualReds() and SCIPallowStrongDualReds(), respectively
1996- Benders' decomposition
1997 + changed SCIPstoreBenderscutCut() in scip_benders.c to SCIPstoreBendersCut(). Where this function used to take a
1998 SCIP_BENDERSCUT pointer, it now accepts a SCIP_BENDERS pointer.
1999 + the functions SCIPsolveBendersSubproblem() no longer accepts the parameter type. The type is not a necessary
2000 argument for the subproblem solving method.
2001 + arguments of functions SCIPbendersSolveSubproblemLP(), SCIPbendersSolveSubproblemCIP(), and SCIPbendersOnlyCheckConvexRelax() changed
2002 - removed SCIPbenderscutGetNAddedCuts() and SCIPbenderscutGetAddedCutData()
2003
2004
2005### New API functions
2006
2007- new argument "onlyifcomplete" in SCIPmatrixCreate() to skip matrix creation right after detecting unsupported constraint types
2008 and new arguments to count statistics when doing a clean-up of inactive variables in the constraints before building the matrix
2009
2010- new argument "threadsafe" in SCIPcopy(), SCIPcopyConsCompression(), SCIPcopyOrig(), SCIPcopyOrigConsCompression and
2011 SCIPcopyBenders(). This argument must only be set to TRUE if the source and target SCIP instances are to be solved in
2012 parallel. Setting this argument to TRUE has a performance cost.
2013
2014- new argument "append" in SCIPsetModifiedDefaultSettingsIpopt()
2015- functions SCIPclearRelaxSolVals(), SCIPsetRelaxSolVal(), SCIPsetRelaxSolVals(), SCIPsetRelaxSolValsSol(), and SCIPmarkRelaxSolValid()
2016 receive an additional argument "relax" to store the relaxation handler as creator of the relaxation solution.
2017
2018- LP:
2019 - SCIProwGetOriginCons() now returns a SCIP_CONS* instead of a SCIP_CONSHDLR*, use SCIProwGetOriginConshdlr() for the previous behavior
2020 - SCIPcreateRowCons() and SCIPcreateEmptyRowCons() now expect a SCIP_CONS* instead of a SCIP_CONSHDLR*,
2021 use SCIPcreateRowConshdlr() and SCIPcreateEmptyRowConshdlr(), respectively, for the previous behavior
2022 - deprecated SCIPlpfeastol() and SCIPchgLpfeastol(), use SCIPgetLPFeastol() and SCIPsetLPFeastol()
2023
2024- new parameter "divecontext" for every method that queries statistics for a diveset. The context can be used to distinguish between the dive set
2025 as single (standalone) heuristic or within Adaptive Diving.
2026- new parameters "divecontext" and "iterlim" to SCIPperformGenericDivingAlgorithm() to control in which context (single,adaptive) statistics are updated.
2027
2028- SCIPcopyVars, SCIPcopy, SCIPcopyConsCompression, and SCIPgetVarCopy do not copy variables that are marked as relaxation-only,
2029 thus it cannot be assumed anymore that each active variable from the master SCIP also has a counterpart in the copy.
2030 SCIPcopy, SCIPcopyConsCompression, and SCIPcopyConss can now return *valid=TRUE if some non-checked and non-enforced constraints were not copied, e.g.,
2031 because they involved relaxation-only variables. Thus, a copy is already regarded as valid if all checked or enforced constraints were copied successfully.
2032
2033- linking constraint handler:
2034 - changed type of vals argument from int* to SCIP_Real* in SCIPcreateConsLinking() and SCIPcreateConsBasicLinking()
2035 - SCIPgetIntvarLinking() has been renamed to SCIPgetLinkvarLinking().
2036 - changed return value of SCIPgetValsLinking() from int* to SCIP_Real*.
2037 - new method SCIPgetBinvarsDataLinking().
2038
2039- SCIPbendersCheckSubproblemOptimality() now returns a boolean indicating whether the subproblem is optimal or not.
2040 Previously this result was returned through a parameter. The change was required to facilitate the integration with
2041 the UG framework.
2042
2043- deleted SCIPcombineTwoInt(), SCIPcombineThreeInt(), SCIPcombineFourInt(); use the appropriate SCIPhashTwo(), ..., SCIPhashSeven() method instead
2044
2045- SCIPsetupBendersSubproblem takes a parameter of the enforcement type.
2046
2047- SCIPcreateNlpiProb takes a hashmap to store the map between the nlrows and the index in the nlrow array.
2048
2049### New API functions
2050
2051- SCIPallowWeakDualReds() and SCIPallowStrongDualReds() replace the deprecated SCIPallowObjProp() and SCIPallowDualReds(), respectively
2052- methods have been added to facilitate the transfer of Benders' decomposition cuts between solvers in UG. These include
2053 SCIPapplyBendersStoredCuts(), SCIPbendersGetNStoredCuts(), SCIPbendersGetStoredCutData() and
2054 SCIPbendersGetStoredCutOrigData().
2055- added SCIPisConvexAbspower()
2056- new functions SCIPsolGetType(), SCIPsolGetRelax(), SCIPsolSetRelax(), SCIPsolSetLPRelaxation(), SCIPsolSetStrongbranch(),
2057 SCIPsolSetPseudo to set or query the new type attribute of a primal solution. The type attribute gives information
2058 about the origin of the solution, ie, whether it was created by a relaxation handler,
2059 by the LP relaxation, by strong branching, by the current pseudo solution, or by a primal heuristic.
2060 The meaning of the argument 'heur' in all creation methods for primal solutions such as SCIPcreateSol() stays unchanged.
2062- new API functions SCIPsetCommonSubscipParams(), SCIPtranslateSubSol(), and SCIPtranslateSubSols() shared by several Large Neighborhood Search heuristics.
2063- new API function SCIPgetLPDualDegeneracy() to get two measures for the dual degeneracy of the current LP
2064- new API functions SCIPdivesetIsAvailable() to check preconditions of a dive set and SCIPdivesetIsPublic() to check if the dive set can be used
2065 by other primal heuristics.
2066- new API functions SCIPcomputeOrbitsSym(), SCIPcomputeOrbitsFilterSym(), SCIPgetPropertiesPerm(), SCIPdetermineBinvarAffectedSym(),
2067 SCIPdetermineNVarsAffectedSym(), SCIPcomputeComponentsSym(), and SCIPextendSubOrbitope(), SCIPgenerateOrbitopeVarsMatrix() for symmetry computations
2068- new API functions SCIPvarIsRelaxationOnly() and SCIPvarMarkRelaxationOnly() to query and set, resp., whether a variable is marked as relaxation-only
2069- new API functions SCIPconshdlrGetNUpdateConss() and SCIPconshdlrGetUpdateConss(), for expert users only
2070- new API function SCIPgetNConflictDualproofsApplied()
2071- new API functions SCIPeventGetOldtype() and SCIPeventGetNewtype() for the new event when changing the variable type
2072- new API function SCIPisConvexConsQuadratic() to check whether a quadratic constraint is convex when a given set of variables would be fixed
2073- new API functions SCIPgetLPFeastol(), SCIPsetLPFeastol(), and SCIPresetLPFeastol() to get, set, and reset (to the default), respectively, the primal
2074 feasibility tolerance for the LP relaxation
2075- new API functions SCIPcleanupConss{Linear,Varbound,Setppc,Logicor,Knapsack}() to clean up inactive variables from those types of linear constraints
2076- new API function SCIPsetBendersSubproblemComp() used to add a custom comparison method for ordering the Benders'
2077 decomposition subproblem solves. The comparison method is used to help with load balancing.
2078- new API function SCIPgetRowObjParallelism to get the objective parallelism of a row
2079- new API function SCIPcolGetAge to get the age of a column
2080- added SCIPhashThree(), SCIPhashFive(), SCIPhashSix(), and SCIPhashSeven() that complement SCIPhashTwo(), SCIPhashFour() to combine 32bit integers to
2081 a 32bit hash value
2082- new API function SCIPgenerateAndApplyBendersOptCut is used to generate a Benders' optimality cut using the dual
2083 solutions. This function can be supplied vectors for the primal and dual solution for generating an optimality cut.
2084 This avoids the need for a SCIP instance to solve the Benders' decomposition subproblem and generating cuts.
2085- new API function SCIPconsAddCoef used for adding a coefficient to a linear-type constraint.
2086- new API functions SCIPconsNonlinearGetRhs, SCIPconsNonlinearGetLhs and SCIPconsNonlinearAddLinearCoef for getting the
2087 RHS and LHS from a nonlinear-type constraint and adding a linear coefficient to the constraint.
2088- new API function SCIPbendersSolSlackVarsActive for checking whether any slack variables from the feasibility phase are
2089 active in the subproblem solution.
2090- new API functions SCIPbendersSetSubproblemType and SCIPbendersGetSubproblemType sets and gets the subproblem type.
2091 This is either:
2092 - Convex constraints with continuous variables
2093 - Convex constraints with discrete variables
2094 - Non-convex constraints with continuous variables
2095 - Non-convex constraints with discrete variables
2096- new API functions SCIPbendersSetSubproblemIsNonlinear() and SCIPbendersSubproblemIsNonlinear() for setting and
2097 identifying whether the Benders' decomposition subproblems contain nonlinear constraints. Similarly, the functions
2098 SCIPbendersSetMasterIsNonlinear() and SCIPbendersMasterIsNonlinear() sets and identifies whether the Benders'
2099 decomposition master problem contains nonlinear constraints.
2100- new API function SCIPapplyBendersDecomposition for applying Benders' decomposition given a decomposition in the DEC
2101 format
2102- new API function SCIPwasNodeLastBranchParent to query if a node has been the parent of the most recent branching in the tree
2103- new API functions SCIPtreemodelInit(), SCIPtreemodelFree(), SCIPtreemodelIsEnabled(), SCIPtreemodelSelectCandidate() related to the new
2104 treemodel way of comparing branching candidates. These functions are only currently used for reliability pscost branching, but they can be used
2105 in other parts of the code.
2106- New function SCIPcalcChildEstimateIncrease() to compute the increase in the child estimation
2107- new API functions SCIPisOrbitalfixingEnabled() and SCIPgetSymmetryNGenerators() to check whether orbital fixing is
2108 enabled and to get the number of generators of the current symmetry group, respectively
2109- new API function SCIPdelNlRow() to remove a row from the NLP
2110
2111### Event system
2112
2113- new event type SCIP_EVENTTYPE_NODEDELETE to react on nodes that are about to be deleted from the tree
2114
2115### Changed parameters
2116
2117- renamed parameter "propagating/orbitalfixing/enableafterrestart" to ".../symmetry/recomputerestart"
2118- Parameter "misc/allowdualreds" is now called "misc/allowstrongdualreds"
2119- Parameter "misc/allowobjprop" is now called "misc/allowweakdualreds"
2120- changed default values of propagation (new value: 1, old value: 5) and separation frequency (new value: -1, old value: 5) in cons_orbitope.c
2121- all primal heuristics that use sub-SCIPs are disabled within the heuristics fast emphasis setting
2122- deleted parameter heuristics/localbranching/useuct, use heuristics/useuctsubscip instead
2123- changed default value of "presolving/symbreak/detectorbitopes" (new value: TRUE, old value: FALSE)
2124- extended range of "misc/usesymmetry" (new range: [0,3], old range: [0,2])
2139- changed default value of "heuristics/coefdiving/freq" (old: 10, new: -1)
2140- changed default value of "heuristics/conflictdiving/freq" (old: -1, new: 10)
2141- changed default value of "heuristics/conflictdiving/lockweight" (old: 1.0, new: 0.75)
2142- replaced parameter "numerics/lpfeastol" by "numerics/lpfeastolfactor" to specify which factor should be applied to the SCIP feasibility
2143 tolerance to initialize the primal feasibility tolerance of the LP solver
2144- enabling aggressive presolving now activates all available presolving plugins,
2145 and decreases the presolving/restartfac parameter correctly with respect to default.
2146- changed default value of heuristics/rins/nodesquot to 0.3 (was 0.1), to compensate
2147 the removal of a hard coded factor of 3.0 in the code without affecting the default behavior
2148 of the RINS heuristic.
2149- changed default value of "constraints/quadratic/empathy4and" (old: 0, new: 2)
2150- changed default value of "propagating/redcost/useimplics" (old: TRUE, new: FALSE)
2151
2152### New parameters
2153
2154- the possibility to define the Benders' decomposition auxiliary variables as implicit integer is provided. This
2155 behavior is controlled with an additional parameter in the Benders' decomposition framework.
2156- added parameter benders/<bendersname>/cutcheck to enable the generation of Benders' decomposition cuts during solution
2157 checking.
2158- constraints/orbitope/usedynamicprop: the possibility to propagate orbitope constraints by reordering the rows based on the
2159 branching strategy is provided (only possible for non-model constraints)
2160
2161- new parameters heuristics/shiftandpropagate/minfixingratelp and heuristics/locks/minfixingratelp to stop the
2162 heuristics after propagating integer fixings if no sufficient fixing of the all variables (including continuous)
2163 could be achieved. These parameters help to avoid solving LP's that are comparable in hardness to the main root LP.
2164
2165- Added parameters branching/midpull and branching/midpullreldomtrig to control by how much to move
2166 the branching point for an external branching candidate closer to the middle of the candidates domain. The
2167 default of 0.75 and 0.5, respectively, uses a point that is 75*alpha% closer to the middle of the domain, where
2168 alpha is the relative width of the candidates domain (width of local domain divided by width of global domain),
2169 if the latter is below 0.5, and alpha=1.0 otherwise. That is, with the default settings, a branching point is
2170 chosen closer to the middle of the candidates domain if the variables local domain is still similar to its
2171 global domain, but is chosen closer to the LP solution if the local domain is much smaller than the global
2172 domain.
2173
2174- Added parameter lp/minmarkowitz to set the Markowitz stability threshold (range 0.0001 to 0.9999).
2175 High values sacrifice performance for stability.
2176
2177- Added parameters benders/<bendersname>/lnsmaxcalls and benders/<bendersname>/lnsmaxcallsroot to the Benders'
2178 decomposition core. These parameters limit the number of Benders' decomposition subproblem checks, for the full
2179 branch-and-bound tree and root node respective, when solving the auxiliary problem of LNS hueristics. These
2180 parameters only have effect if the lnscheck parameter is set to TRUE.
2181
2182- Added parameter cons/linear/maxmultaggrquot to limit the maximum coefficient dynamism of an equation on which
2183 multiaggregation is performed. This replaces a compiler define of the same name.
2184 Default value is 1000, smaller values make multiaggregations numerically more stable.
2185- new global parameter heuristics/useuctsubscip that affects all LNS heuristics using common sub-SCIP parameters
2186
2187- new parameter branching/relpscost/degeneracyaware to switch degeneracy-aware hybrid branching
2188
2189- new parameter separation/rapidlearning/checkexec to check whether rapid learning is allowed to run locally
2190- new parameters separation/rapidlearning/check{degeneracy,dualbound,leaves,nsols,obj} to enable checking the respective feature for local rapid learning
2191- new parameter separation/rapidlearning/maxcalls to limit the number of rapid learning executions
2192- new parameter separation/rapidlearning/nwaitingnodes to set the number of waiting nodes before the dual bound is checked
2193- new parameter separation/rapidlearning/mindegeneracy to set the minimal threshold of degenerate basic-variables
2194- new parameters separation/rapidlearning/minvarconsratio to set the minimal ratio of unfixed variables in relation to basis size
2195
2196- new parameters to control the Benders' decomposition two-phase method.
2197 - constraints/benderslp/depthfreq: after the maxdepth is reached, then the two-phase method will only be called at
2198 nodes at a depth divisible by depthfreq.
2199 - constraints/benderslp/stalllimit: after the maxdepth is reached, if there has been no improvement in the dual bound
2200 for stalllimit number of nodes, then the two-phase method is executed for the next fractional LP solution that is
2201 encountered.
2202 - constraints/benderslp/iterlimit: after the root node, only iterlimit fractional LP solutions are used at each node
2203 to generate Benders' decomposition cuts.
2204
2205- new parameters for symmetry handling
2206 - new parameter "propagating/symmetry/maxgenerators"
2207 - new parameter "propagating/symmetry/checksymmetries"
2208 - new parameter "propagating/symmetry/displaynorbitvars"
2209 - new parameter "propagating/symmetry/conssaddlp"
2210 - new parameter "propagating/symmetry/addsymresacks"
2211 - new parameter "propagating/symmetry/detectorbitopes"
2212 - new parameter "propagating/symmetry/addconsstiming"
2213 - new parameter "propagating/symmetry/ofsymcomptiming"
2214 - new parameter "propagating/symmetry/performpresolving"
2215 - new parameter "propagating/symmetry/recomputerestart"
2216 - new parameter "constraints/symresack/checkmonotonicity"
2217 - new parameter "propagating/symmetry/compresssymmetries"
2218 - new parameter "propagating/symmetry/compressthreshold"
2219 - new parameter "propagating/symmetry/disableofrestart"
2220 - new parameter "propagating/symmetry/symfixnonbinaryvars"
2221
2222- new parameter for enabling shared memory parallelisation for solving Benders' decomposition subproblems. The parameter
2223 benders/<bendersname>/numthreads sets the number of threads used for parallel subproblem solving.
2224
2225- new parameters to control enhancements for solving MINLPs by Benders' decomposition
2226 - benders/<bendersname>/execfeasphase: enables the feasibility phase for solving the Benders' decomposition
2227 subproblems
2228 - benders/<bendersname>/slackvarcoef: the initial coefficient of the slack variable for the feasibility phase
2229 - benders/<bendersname>/checkconsconvexity: should the constraints be checked for convexity. This can be set to FALSE
2230 if you are certain that the NLP subproblem is convex.
2231
2232- new parameter presolving/clqtablefac (default value 2.0) as limit on number of entries in clique table relative to number of problem nonzeros
2233
2234- new parameter conflict/uselocalrows (default: TRUE) to incorporate locally valid cuts / rows for dual proof analysis
2235
2236- new return code SCIP_NOTIMPLEMENTED for functions, e.g., in the LPI that have not been implemented (yet)
2237
2238- new parameter separating/cgmip/genprimalsols that allows to generate initial primal solutions from Gomory cuts
2239
2240- new parameter branching/relpscost/filtercandssym to allow filtering from orbits
2241
2242- new parameter branching/relpscost/transsympscost to transfer pseudo cost information to orbit
2243
2244- new parameters for tree size estimation and restarts:
2245 - estimation/restarts/restartpolicy (default value n)
2246 - estimation/method (default value c)
2247 - estimation/restarts/restartlimit (default value 1)
2248 - estimation/restarts/minnodes (default value 1000)
2249 - estimation/restarts/countonlyleaves (default value FALSE)
2250 - estimation/restarts/restartfactor (default value 2)
2251 - estimation/coefmonoprog (default value 0.3667)
2252 - estimation/coefmonossg (default value 0.6333)
2253 - estimation/restarts/hitcounterlim (default value 50)
2254 - estimation/reportfreq (default value -1)
2255 - estimation/regforestfilename (default value "-")
2256 - estimation/completiontype (default value a)
2257 - estimation/treeprofile/enabled (default value FALSE)
2258 - estimation/treeprofile/minnodesperdepth (default value 20)
2259 - estimation/useleafts (default value TRUE)
2260 - estimation/ssg/nmaxsubtrees (default value -1)
2261 - estimation/ssg/nminnodeslastsplit (default value 0)
2262
2263- new parameter constraints/linear/extractcliques to turn clique extraction off
2264
2265- new emphasis setting emphasis/numerics to increase numerical stability of (mostly) presolving operations such as (multi-)aggregations at the cost of performance.
2266
2267- new parameters for treemodel:
2268 - new parameter branching/treemodel/enable to enable the treemodel in reliability pscost branching and possible
2269 future parts of the code where it could be used.
2270 - new parameter branching/treemodel/highrule to specify which branching rule to use when treemodel thinks the node
2271 is high in the tree.
2272 - new parameter branching/treemodel/lowrule to specify which branching rule to use when treemodel thinks the node
2273 is low in the tree.
2274 - new parameter branching/treemodel/height to specify at which (estimated) height a node is high or low in the tree.
2275 - new parameter branching/treemodel/filterhigh to specify whether to filter dominated candidates in nodes which are
2276 high in the tree.
2277 - new parameter branching/treemodel/filterlow to specify whether to filter dominated candidates in nodes which are
2278 low in the tree.
2279 - new parameter branching/treemodel/maxfpiter to specify the maximum number of fixed-point iterations to use when
2280 computing the ratio of a variable using the fixed-point method.
2281 - new parameter branching/treemodel/maxsvtsheight to specify the maximum height to compute the SVTS score exactly
2282 before approximating it using the ratio.
2283 - new parameter branching/treemodel/fallbackinf defines the fallback strategy to use when the tree size estimates
2284 obtained by SVTS are infinite.
2285 - new parameter branching/treemodel/fallbacknoprim defines the fallback strategy to use when no primal bound is known
2286 and thus SVTS would not be able to compute a tree size (it would be infinite).
2287 - new parameter branching/treemodel/smallpscost defines the value under which pscosts are considered too small to be
2288 the deciding factor for branching, in which case it may be better not to use the treemodel.
2289
2290- new parameters for symmetry handling constraint handlers to enforce that also non-model constraint are copied:
2291 - new parameter "constraints/orbisack/forceconscopy"
2292 - new parameter "constraints/orbitope/forceconscopy"
2293 - new parameter "constraints/symresack/forceconscopy"
2294
2295
2296### Data structures
2297
2298- small changes in constants of hash functions
2299- added fast 2-universal hash functions for two to seven 32bit elements with 32bit output
2300- extended SCIPpqueueCreate() by additional callback argument SCIP_DECL_PQUEUEELEMCHGPOS to catch position changes
2301- new methods SCIPpqueueDelPos() to delete elements at a specific position in the priority queue and SCIPpqueueFind() to
2302 find a specific position. It is recommended to track position changes using the new callback SCIP_DECL_PQUEUEELEMCHGPOS.
2303 In contrast, using SCIPpqueueFind() can be slow because it needs to compare the element it searches for
2304 with each slot in the queue.
2305
2306### Build system
2307
2308- The default value for DFLAGS in the non-cmake buildsystem has changed from -MM to -MMD. This will break the
2309 generation of depend.* files if that was done by a compiler call that relied on -MM. The new preferred way
2310 to handle compilation dependencies is to additionally use $(DFLAGS) when compiling the object files (.o) and
2311 to include the generated .d files in the Makefile, see also "Build system / Makefile" below.
2312
2313Unit tests
2314----------
2315 - new unit test for treemodel.
2316
2317Testing
2318-------
2319
2320 - fixed an issue that may have lead to wrong status reports in the evaluation scripts
2321
2322Build system
2323------------
2324
2325### Cmake
2326
2327- avoid problem with doubly defined object together with CPLEX
2328
2329### Makefile
2330
2331- Removed static object compilation dependency files (depend.*). If using a GCC compatible compiler, then dependency
2332 files are now dynamically created and updated during build. The new dependency files (*.d) reside next to each object
2333 file (.o) in the corresponding obj subdirectory.
2334- added support for building against Ipopt >= 3.13
2335- unify compiler switches for Intel compiler and avoid problem with doubly defined object together with CPLEX
2336
2337Fixed bugs
2338----------
2339
2340- fix and improve memory handling in symmetry computation
2341- fix shown number of applied conflicts in solving statistics
2342- fix wrongly skipping strong branching call and using old information if LP was solved with 0 iterations
2343- fix minor bug in cut score calculation
2344- fixed several bugs related to rounding locks of variables not being updated correctly
2345- small fix in cons_varbound.c to skip changing bounds of multi-aggregated variables in separation callback
2346- fixed issue in SCIPtightenVar* and SCIPinferVar* that occurs for small bound changes
2347- fixed rejecting minimal boundchange that changed sign of variable, even though SCIPisLb/UbBetter approved it
2348- fixed issue in generateCutNonConvex() which is triggered when adding quadratic constraints during the solving process
2349- fixed bug in freeing the reoptimization data if no problem exists
2350- fixed bug in SCIPreoptReleaseData() when freeing all stored constraints
2351- fixed bug when freeing the transformed problem via interactive shell if reoptimization is enabled
2352- fixed two issues related to (near-)redundant logicor constraints in presolving
2353- fixed counting of aggregations in XOR constraint handler
2354- fixed handling of unbounded solutions
2355- fixed update of LP size information when an LP error occured during probing
2356- handle special case of variable bound constraints during aggregating variables
2357- tighten sides of linear constraints before trying to upgrade them to more specialized constraints (knapsack, logic-or etc.) when calling SCIPupgradeConsLinear()
2358- fixed an issue in repair heuristic in the case of loose (noncolumn) variables
2359- allow user to correctly set heuristics/alns/(un)fixtol
2360- fixed an issue in heur_completesol which is triggered during bound widening of unbounded continuous variables
2361- fixed bug in cons_indicator if addopposite is true
2362- fixed bug in sepa_disjunctive: treat case that conflictgraph is empty
2363- added safety check in conversion to rational number to avoid overflow
2364- fixed bug in interval evaluation with power-operator in certain situations
2365- fixed behavior of SCIPmatrixCreate() regarding memory management and column generation
2366- SCIPmatrixCreate() returns complete=FALSE when locks do not add up
2367- fixed bug in sepa_oddcylce when variables are fixed
2368- fixed numerical issues related to tighter constraint sides in varbound constraint handler
2369- fixed update of watchedvars in logicor constraint handler in case of a restart during the tree
2370- fixed treatment of multi-aggregated variables in logicor constraint handler
2371- handle special case of redundant implications
2372- fixed numerical issue related to almost-0-values in pseudosolution conflict analysis
2373- fixed numerical issue related to very large greatest common dividers in linear constraint handler
2374- avoid using implications on multiaggregated variables when propagating implications
2375- fixed creation of (Lagrangian) variable bounds in the OBBT propagator
2376- fixed sorting of primal solutions
2377- fixed cleaning of clean buffer in conflict analysis
2378- avoid probing on variables with huge bounds in shift and propagate heuristic
2379- fix issue in printing solutions for variables that have been added by the dual sparsify presolver
2380- fix issue related to fixing redundant logic-or constraints after presolving
2381- fixed bug when parsing logic-or and and-constraints
2382- fixed wrong assert in updateLazyBounds()
2383- fixed bug in pricestore, which resulted in too many problem variables being added
2384- fixed bug in cons_knapsack where weight of clique was not reset after an infeasibility was detected
2385- fixed bug in presol_inttobinary which did not take into account that the aggregation could be rejected due to numerics
2386- fixed bug in debug solution mechanism in connection to variables created by presol_inttobinary
2387- fixed wrong indexing while undoing the implications from a redundant variable in SCIPshrinkDisjunctiveVarSet
2388- redundancy checks in SCIPnodeAddBoundinfer now take a possible change to an active variable into account
2389- fixed adding already added quadratic rows to NLP relaxation during solve
2390- fixed issue related to variable locks in the varbound constraint handler
2391- fixed bug in the quadratic constraint handler when changing infinite constraint sides
2392- fixed sorting of variables in linear constraint handler
2393- added additional checks to ensure numerical stability of dual proofs
2394- fixed a case when activities of a linear constraint got unreliable but where still used for reductions
2395- ensure that lhs <= rhs for linear constraints (without tolerances)
2396- make handling of read errors in SCIPfread() consistent between version with and without ZLIB
2397- correctly drop variable events in cons_indicator in restart
2398- fixed bug in cons_orbitope with upgrading of orbitope constraints
2399- additional checks in some presolvers for time limit being exceeded
2400- fixed bug in presolving of cons_varbound with multi-aggregated variables
2401- improve numerics in conflict analysis by using double-double arithmetic
2402- fixed bound acceptance condition to avoid inconsistencies
2403- fixed numerics in pseudoobj propagator by using double-double arithmetic
2404
2405Miscellaneous
2406-------------
2407
2408- modified display column for memory usage ("mem"), which reports the memory usage most of the time, but shows the creator name
2409 (heuristic, relaxation handler, LP relaxation, strong branching, pseudo solution) of every new incumbent solution. Together with this change,
2410 heuristic display characters have been unified to represent the type of the heuristic
2411 (diving, Large neighborhood search, propagation, etc.), see also type_heur.h.
2412- added assert that ensures that the locks of a variable have been decreased to 0 when it is freed
2413- added more output for completing a partial solution
2414- checks in debug mode that clean buffer memory is really clean when being freed are now disabled by default
2415- don't compute symmetries if reoptimization is enabled
2416- prefer integral values when fixing an almost-fixed continuous variable in the trivial presolver
2417- changed the name of the variable that is added by the OSiL reader to represent the quadratic or nonlinear parts of the objective function
2418- SCIP_EXPORT is now defined as __attribute__((__visibility__("default"))) if GCC and no SCIP config header is used
2419
2420@page RN60 Release notes for SCIP 6.0
2421
2422@section RN602 SCIP 6.0.2
2423*************************
2424
2425Features
2426--------
2427
2428- The abspower constraint handler now passes more accurate convexity
2429 information to the NLP relaxation.
2430
2431Examples and applications
2432-------------------------
2433
2434- added parsing functionality for optcumulative constraints in CIP format
2435
2436Interface changes
2437-----------------
2438
2439### Interfaces to external software
2440
2441- Updated the Mosek LP solver interface to support Mosek 9.0.
2442
2443Build system
2444------------
2445
2446### Cmake
2447
2448- new target to 'doc' to build documentation
2449- ctests now fail if parameter file not found
2450- add flag STATIC_GMP and improve GMP find module
2451- remove non-API methods from library (API methods use new macro SCIP_EXPORT)
2452- increase minimal required CMake version to 3.3
2453- correct paths and dependency information when installing SCIP
2454
2455Fixed bugs
2456----------
2457- fixed SCIP-Jack presolving bug that could lead to wrong results for Steiner arborescence problems
2458- fixed wrong unboundedness result in case not all constraints were already in the LP and enforcement was
2459 skipped because an optimal solution was found
2460- fixed wrong enforcement of constraints in the disjunction constraint handler
2461- fixed wrong behavior of concurrent solve ignoring initial solutions
2462- fixed bug in concurrent solve when problem was already solved in presolving
2463- aggregate non-artificial integer variable for XOR constraints with two binary variables and delete constraint
2464- copy the objective offset when copying the original problem
2465- fixed bug in SCIPlpiGetBInvARow in lpi_cpx using wrong size of resulting vector
2466- fixed quadratic runtime behavior in sepa_aggregation
2467- fixed statistics of separators
2468- improve numerical stability in varbound constraint handler by using double-double arithmetic
2469- fixed bug in propagation of dual proofs
2470- fixed bugs that arise for multiaggregated indicator variables by disallowing multiaggregation for them
2471- improve numerical stability in SCIPcomputeBilinEnvelope* by using double-double arithmetic
2472- fixed bug related to releasing pending bound changes in tree.c
2473- set STD FENV_ACCESS pragma to on in code that changes floating-point rounding mode
2474- disable GCC optimizations in main interval arithmetic code to prevent wrong optimizations
2475- fixed wrong assert in cons_xor concerning the variable type
2476- fixed different behavior of SCIPisLbBetter and SCIPisUbBetter between having NDEBUG defined or not
2477- correctly handle bound disjunctions in symmetry detection
2478- fixed issue in reliability branching related to the LP error flag not being reset
2479- fixed treatment of near-infinite bounds in shiftandpropagate's problem transformation
2480- fixed handling of infinite values in SCIPcomputeHyperplaneThreePoints()
2481- fixed comparisons of infinite values in heur_intshifting.c and heur_shifting.c
2482- fixed bug related to updating unprocessed cuts in the cutpool
2483- fixed bug related to enabling quadratic constraints during `CONSINITLP`
2484- add missing SCIP_EXPORT for functions used by GCG
2485- fixed memory leak and wrong initialization for trival cases in cons_symresack.c
2486- fixed bug with upgrading to packing/partitioning orbitopes
2487- fixed bug with the status while upgrading in presol_symbreak.c
2488- fixed wrong stage while clearing the conflict store
2489- fixed behavior of SCIPfixVar() by setting infeasible pointer to TRUE if fixval lies outside variable domain
2490- allow tightenVar() in SCIP_STAGE_PROBLEM stage
2491- fixed bug in cumulative constraint handler when separating the LP solution
2492- fixed issues with integer overflow in cumulative constraint handler
2493- fixed bug where the convexity of Benders' decomposition subproblems was checked even when users defined subproblem
2494 solving methods. Now, as per the documentation, the user must explicitly state whether the subproblem is convex
2495- fixed wrong indexing in heur_dualval
2496- fixed issue with basis status in SoPlex LPi
2497
2498Miscellaneous
2499-------------
2500
2501- statistics now output primal/dual bounds if objective limit is reached
2502- memory check in debug mode is now disabled by default
2503- message is now provided to the user to inform that automatic Benders' auxiliary variable lower bound computations are
2504 not activated when user defined subproblem solving methods are present
2505- corrected documentation of the primalgap in SCIP; describe when it will be infinite
2506
2507@section RN601 SCIP 6.0.1
2508*************************
2509
2510Features
2511--------
2512
2513- when using a debug solution every (multi-)aggregation will be checked w.r.t. this solution
2514
2515Performance improvements
2516------------------------
2517
2518- try greedy solution first before solving knapsack exactly using dynamic programming in SCIPsolveKnapsackExactly,
2519 compute greedy solution by weighted median selection.
2520- don't consider implied redcost by default in the reduced cost propagator
2521
2522Interface changes
2523-----------------
2524
2525### Deleted and changed API methods and macros
2526
2527- The preprocessor macro NO_CONFIG_HEADER now needs to be defined when
2528 including SCIP header files from a SCIP build or installation that
2529 has been build via the Makefile-only build system.
2530
2531- The following preprocessor macros have been renamed:
2532 WITH_ZLIB to SCIP_WITH_ZLIB, WITH_GMP to SCIP_WITH_GMP, WITH_READLINE
2533 to SCIP_WITH_READLINE, NO_SIGACTION to SCIP_NO_SIGACTION, NO_STRTOK_R
2534 to SCIP_NO_STRTOK_R, ROUNDING_FE to SCIP_ROUNDING_FE, ROUNDING_FP to
2535 SCIP_ROUNDING_FP, ROUNDING_MS to SCIP_ROUNDING_MS. Note, however, that
2536 the names of macros NO_RAND_R and NO_STRERROR_R have not been changed
2537 so far.
2538
2539### New API functions
2540
2541- SCIPhashmapInsertInt(), SCIPhashmapSetImageInt(), and SCIPhashmapGetImageInt() to use integer values as images in hashmaps
2542
2543### Command line interface
2544
2545- warn about coefficients in MPS files with absolute value larger than SCIP's value for infinity
2546
2547### Changed parameters
2548
2549- default clock type for timing is now wallclock
2550
2551Unit tests
2552----------
2553
2554- added unit tests for exact knapsack solving and (weighted) median selection algorithms
2555
2556Build system
2557------------
2558
2559### Cmake
2560
2561- add missing GMP dependency when compiling with SYM=bliss
2562- add DL library when linking to CPLEX to avoid linker errors
2563- new config.h header defining the current build configuration, e.g. SCIP_WITH_GMP
2564
2565Fixed bugs
2566----------
2567
2568- fixed handling of weights in cons_sos1 and cons_sos2 (NULL pointer to weights)
2569- fixed handling of unbounded LPs in SCIP and in several LPIs; added heuristic method to guess solution
2570- the STO reader is capable of handling scenarios defined using lower case "rhs"
2571- fixed OPB reader for instances without explicit plus signs
2572- correct dual solution values for bound constraints
2573- fixed recognition of variable with only one lock in cons_bivariate, cons_quadratic, and cons_nonlinear
2574- fixed update of constraint violations in solution repair in cons_bivariate, cons_quadratic, and cons_nonlinear
2575- print error message and terminate if matrix entries of a column are not consecutive in mps format
2576- fixed incorrect handling of fixed variables when transfer of cuts from LNS heuristic for Benders' decomposition
2577- fix returning local infeasible status by Ipopt interface if Ipopt finds problem locally infeasible
2578- skip attempt to apply fixings in linear constraint handler during solving stage as LP rows cannot change anymore
2579- fixed bug when reading >= indicator constraints in MPS format
2580- fix issue with nodes without domain changes if we ran into solution limit in prop_orbitalfixing
2581- fixed unresolved reference to CppAD's microsoft_timer() function on builds with MS/Intel compilers on Windows
2582- ignore implications added through SCIPaddVarImplication() that are redundant to global bounds also in the
2583 special case of an implication between two binary variables; also, use implications instead of cliques in the case
2584 of a binary implied variable with nonbinary active representative
2585- fixed bug with aggregated variables that are aggregated in propagation of cons_sos1
2586- fixed some special cases in SCIPselect/SCIPselectWeighted methods
2587- relaxed too strict assertion in Zirounding heuristic
2588- fixed the upgrade routine to XOR constraints: aggregate integer variable if its coefficient has the wrong sign
2589- fixed handling of nonartificial parity variables when deleting redundant XOR constraints
2590- earlier deletion of trivial XOR constraints (at most 1 operator left)
2591- fixed wrong hashmap accesses and added sanity check for the correct hashmap type
2592- avoid copying of unbounded solutions from sub-SCIPs as those cannot be checked completely
2593- corrected the output of the first LP value in case of branch-and-price
2594- fixed possible integer overflow, which led to wrong conclusion of infeasibility, in energetic reasoning of cons_cumulative.c
2595
2596Miscellaneous
2597-------------
2598
2599- do not scale linear constraints to integral coefficients
2600
2601@section RN600 SCIP 6.0.0
2602*************************
2603
2604Features
2605--------
2606
2607- new diving heuristic farkasdiving that dives into the direction of the pseudosolution and tries to construct Farkas-proofs
2608- new diving heuristic conflictdiving that considers locks from conflict constraints
2609- restructuring of timing of symmetry computation that allows to add symmetry handling components within presolving
2610- `lp/checkstability` is properly implemented for SoPlex LPI (spx2)
2611- new branching rule lookahead that evaluates potential child and grandchild nodes to determine a branching decision
2612- limits on the number of presolving rounds a presolver (maxrounds) or propagator/constraint handler (maxprerounds)
2613 participates in are now compared to the number of calls of the particular presolving method, not the number of
2614 presolving rounds in general, anymore
2615- new miscellaneous methods for constraints that have a one-row linear representation in pub_misc_linear.h
2616- a Benders' decomposition framework has been added. This framework provides the functionality for a user to solve a
2617 decomposed problem using Benders' decomposition. The framework includes classical optimality and feasibility cuts,
2618 integer optimality cuts and no-good cuts.
2619- add statistic that presents the number of resolves for instable LPs
2620- new readers for stochastic programming problems in SMPS format (reader_sto.h, reader_smps.h)
2621
2622Performance improvements
2623------------------------
2624
2625- cuts generated from certain quadratic constraints with convex feasible region are now global
2626- performance improvements for Adaptive Large Neighborhood Search heur_alns.c
2627 + all neighborhoods now start conservatively from maximum fixing rate
2628 + new default parameter settings for bandit selection parameters
2629 + no adjustment of minimum improvement by default
2630- improved bound tightening for some quadratic equations
2631- constraint handler checking order for original solutions has been modified to check those with negative check priority
2632 that don't need constraints after all other constraint handlers and constraints have been checked
2633- deactivate gauge cuts
2634
2635Examples and applications
2636-------------------------
2637
2638- new example `brachistochrone` in CallableLibrary examples collection; this example implements a discretized model to
2639 obtain the trajectory associated with the shortest time to go from point A to B for a particle under gravity only
2640- new example `circlepacking` in CallableLibrary examples collection; this example models two problems about packing
2641 circles of given radii into a rectangle
2642- new price-and-branch application for the ringpacking problem
2643- new stochastic capacitated facility location example demonstrating the use of the Benders' decomposition framework
2644
2645Interface changes
2646-----------------
2647
2648### New and changed callbacks
2649
2650- added parameter locktype to `SCIP_DECL_CONSLOCK` callback to indicate the type of variable locks
2651
2652### Deleted and changed API methods
2653
2654- Symmetry:
2655 + removed function SCIPgetTimingSymmetry() in presol_symmetry.h since this presolver does not compute symmetries independent
2656 of other components anymore
2657 + additional argument `recompute` to SCIPgetGeneratorsSymmetry() to allow recomputation of symmetries
2658
2659- Random generators:
2660 + the seed of SCIPinitializeRandomSeed() is now an unsigned int
2661 + the seed of SCIPsetInitializeRandomSeed() is now an unsigned int and it returns an unsigned int
2662 + new parameter for SCIPcreateRandom() to specify whether the global random seed shift should be used in the creation of
2663 the random number generator
2664
2665- Miscellaneous:
2666 + additional arguments `preferrecent`, `decayfactor` and `avglim` to SCIPcreateBanditEpsgreedy() to choose between
2667 weights that are simple averages or higher weights for more recent observations (the previous default).
2668 The last two parameters are used for a finer control of the exponential decay.
2669 + functions SCIPintervalSolveUnivariateQuadExpression(), SCIPintervalSolveUnivariateQuadExpressionPositive(), and
2670 SCIPintervalSolveUnivariateQuadExpressionPositiveAllScalar() now take an additional argument to specify already
2671 existing bounds on x, providing an entire interval ([-infinity,infinity]) gives previous behavior
5767 - added writing for pip files (linear, quadratic, polynomial nonlinear, polynomial abspower, polynomial bivariate, and
5768 and constraints)
5769 - CIP format variable characters defined, e.g. `SCIP_VARTYPE_INTEGER_CHAR`
5770 - Improved support for wbo format for weighted PBO problems, IBM's xml-solution
5771 format and pip and zimpl format for polynomial mixed-integer programs
5772 - New reader for (standard) bounds on variables
5773 - Extended reader for CIP models to handle various new constraints, including all types of linear constraints
5774 - flatzinc reader is now capable to read cumulative constraints
5775 - changed opb(/wbo) reader which now creates pseudoboolean constraints instead of linear- and and-constraints, only a
5776 non-linear objective will create and-constraints inside the reader and while reading a wbo file the topcost constraint
5777 is created as well
5778 - added clock for determine the time for reading
5779 - added reader for variable bounds (reader_bnd.{c,h})
5780 - Removed method SCIPreadSol(); call solution reading via SCIPreadProb() which calls the solution reader for .sol files.
5781
5782- Nonlinear:
5783 - Major extensions for nonlinear CIP, new option for n-ary branching on nonlinear variables (within pseudocost branching rule)
5784 - added BETA version of constraint handler for nonlinear constraints (cons_nonlinear.{c,h}) to handle nonlinear
5785 equations given by algebraic expressions using operands like addition, multiplication, power, exp, log, bivariate
5786 nonlinear constraints; currently no trigonometric functions
5787 - added BETA version of constraint handler for bivariate nonlinear constraints (cons_bivariate.{c,h}) to compute tight
5788 estimators for 1-convex and convex-concave bivariate nonlinear functions (given as expression tree)
5789 - the gams writer can now write nonlinear, abspower and bivariate constraints
5790 - Extended writer for GAMS and pip format to write more types of nonlinear constraints
5791 - the pip and zimpl reader now create nonlinear constraints for polynomials of degree > 2
5792
5793- Presolving:
5794 - new dual presolving methods in cons_setppc and cons_logicor
5795 - new presolving step `removeConstraintsDueToNegCliques` in locigor constraint handler which updates logicor constraints
5796 to setppc constraints if a negated clique inside this constraint exist, by default is off
5797 - new presolving step in cons_knapsack (detectRedundantVars, deleteRedundantVars) which determines redundant variables
5798 in knapsack constraint with or without using clique information
5799 - cons_logicor is now able to replace all aggregated variables in presolving by there active or negation of an active
5800 variable counterpart
5801 - prop_pseudoobj is now working in presolving as well
5802 - implement presolving in exitpre() in cons_orbitope and cons_indicator
5803
5804- Propagators:
5805 - added counter for number calls and timing for resolve propagation calls for constraint handler and propagators
5806 - Propagators are now also called in node presolving
5807 - the probing presolver presol_probing.{c.h} is now a propagator prop_probing.{c,h}, all corresponding parameters moved as well
5808 - the redcost separator sepa_redcost.{c.h} is now a propagator prop_redcost.{c,h}, all corresponding parameters moved as well
5809 - outsourced propAndSolve() method in solve.c which calls domain propagation and solving of the lp and relaxation
5810
5811- Statistic:
5812 - solutions which are given by the user from the outside are now marked by `#` in the output
5813 - the `Solving Time` is now spitted into presolving, solving and reading time
5814 - Presolvers section has new column `AddCons` which states the number of added constraint
5815 - Constraints section has new column named \#ResProp which show the number of resolve propagation calls of certain
5816 constraint handler
5817 - Constraint Timing section has a new column \#ResProp which states the time spend in resolve propagation method of the
5818 constraint handler
5819 - improved output of propagators in display statistics
5820 - new section `Propagator Timing` which shows the time spend in different callbacks of the propagator
5821 - rearranged first two columns of Propagators section; \#Propagate and \#ResProp stating the number of call for
5822 propagation and resolve propagation; the Time column is moved into the new section Propagator Timings
5823 - Constraints section has new column named `MaxNumber` which the maximum number of active constraint of a certain
5824 constraint handler
5825 - added two columns `Time-0-It` and `Calls-0-It` in the LP section which states the number of LP call and time spend for
5826 solving LPs with zero iterations (only refactorization)
5827 - The display of statistics for presolvers, propagators, constraints and LP solving has changed.
5828
5829Performance improvements
5830------------------------
5831
5832- Reorganized filtering process of separation storage (allows adding cuts for different solutions)
5833- Improved presolving for various constraint handlers
5834- Improved propagation methods for variable bound constraints
5835- Improved performance for quadratic constraints
5836- performance improvements in prop_vbounds
5837- child selection rules now get also applied when the relaxation value is equal to the bound changed in branching
5838- added dual reduction to cons_cumulative.c
5839- for continuous variables, the pseudo costs update and the pscost branching rule now use the same strategies for
5840 updating the pseudo costs and estimating the improvement in the LP bound
5841- only perform probing if the variables are locked
5842- performance and memory consumption improvements in xmlparse.c
5843- Improved knapsack cover cuts
5844- avoid very long separation times of LEWIs in cons_knapsack for very large minimal covers
5845- used SCIPallocMemoryArray() instead of SCIPallocBlockMemoryArray() which leads to fewer memory consumption in
5846 getLiftingSequence() in cons_knapsack, also improved cache use bei using an extra array instead blockmemory chunks
5847- switched FASTMIP from 1 to 2 for CPLEX and changed default pricing rule back to steepest edge pricing instead of
5848 quickstart steepest edge pricing
5849- made sorting method more robust
5850- LNS heuristics now use SCIPcopy() by default
5851- considering inactive variables in undercover heuristic; limiting effort for solving covering problem
5852- if during probing mode the LP relaxation is solved from scratch, e.g., when calling the shiftandpropagate heuristic
5853 before root node solving, then we clear the resulting LP state, since it might be a bad starting basis for the next
5854 solve of the LP relaxation (controlled by new parameter `lp/clearinitialprobinglp`)
5855- included LP simplifier into SoPlex LP interface, applied when solving from scratch (lpi_spx.cpp)
5856- new presolving steps in varbound constraint handler, tightening bounds, coefficients, sides and pairwise presolving
5857
5858Interface changes
5859-----------------
5860
5861- Miscellaneous:
5862 - The emphasis setting types now distinguish between plugin-type specific parameter settings (default, aggressive, fast, off),
5863 which are changed by SCIPsetHeuristics/Presolving/Separating(), and global emphasis settings (default, cpsolver, easycip,
5864 feasibility, hardlp, optimality, counter), which can be set using SCIPsetEmphasis().
5865
5866### New and changed callbacks
5867
5868- added propagator timings `SCIP_PROPTIMING_BEFORELP`, `SCIP_PROPTIMING_DURINGLPLOOP` and `SCIP_PROPTIMING_AFTERLPLOOP` for
5869 all propagation callbacks (see propagators and constraint handlers) which lead to calling the propagation methods of a
5870 propagator before the lp is solved, during the lp loop and after the lp solving loop
5871
5872- Conflict Analysis:
5873 - Added parameter `separate` to conflict handler callback method SCIP_DECL_CONFLICTEXEC() that defines whether the conflict
5874 constraint should be separated or not.
5875
5876- Constraint Handler:
5877 - The new constraint handler callback SCIP_DECL_CONSDELVARS() is called after variables were marked for deletion.
5878 This method is optional and only of interest if you are using SCIP as a branch-and-price framework. That means,
5879 you are generating new variables during the search. If you are not doing that just define the function pointer
5880 to be `NULL`.
5881 If this method gets implemented you should iterate over all constraints of the constraint handler and delete all
5882 variables that were marked for deletion by SCIPdelVar().
5883
5884- NLP Solver Interface:
5885 - The callbacks SCIP_DECL_NLPIGETSOLUTION() and SCIP_DECL_NLPISETINITIALGUESS() got new parameters to get/set values of
5886 dual variables.
5887 - The callback SCIP_DECL_NLPICOPY() now passes the block memory of the target SCIP as an additional parameter.
5888
5889- Presolving:
5890 - New parameters `isunbounded` and `isinfeasible` for presolving initialization (SCIP_DECL_CONSINITPRE(),
5891 SCIP_DECL_PRESOLINITPRE(), SCIP_DECL_PROPINITPRE()) and presolving deinitialization (SCIP_DECL_CONSEXITPRE(),
5892 SCIP_DECL_PRESOLEXITPRE(), SCIP_DECL_PROPEXITPRE()) callbacks of presolvers,
5893 constraint handlers and propagators, telling the callback whether the problem was already declared to be
5894 unbounded or infeasible. This allows to avoid expensive steps in these methods in case the problem is already
5895 solved, anyway.
5896
5897 Note, that the C++ methods
5898 - scip::ObjConshdlr::scip_presol() corresponding to SCIP_DECL_CONSPRESOL()
5899 - scip::ObjConshdlr::scip_initpre() corresponding to SCIP_DECL_CONSINITPRE()
5900 - scip::ObjPresol::scip_initpre() corresponding to SCIP_DECL_PRESOLINITPRE()
5901 - scip::ObjProp::scip_initpre() corresponding to SCIP_DECL_PROPINITPRE()
5902 - scip::ObjConshdlr::scip_exitpre() corresponding to SCIP_DECL_CONSEXITPRE()
5903 - scip::ObjPresol::scip_exitpre() corresponding to SCIP_DECL_PRESOLEXITPRE()
5904 - scip::ObjProp::scip_exitpre() corresponding to and SCIP_DECL_PROPEXITPRE()
5905 are virtual functions. That means, if you are not adding the new parameters, your code will still compile, but these methods are not executed.
5906 - Propagators are now also called in during presolving, this is supported by the new callback methods SCIP_DECL_PROPINITPRE(),
5907 SCIP_DECL_PROPEXITPRE(), and SCIP_DECL_PROPPRESOL().
5908 - The new parameters `nnewaddconss` and `naddconss` were added to the constraint handler callback method SCIP_DECL_CONSPRESOL()
5909 and the presolver callback method SCIP_DECL_PRESOLEXEC(). These parameters were also added to corresponding C++ wrapper
5910 class methods (scip_presol() in objconshdlr.h and scip_exec() in objpresol.h)
5911
5912- Problem Data:
5913 - The callback SCIP_DECL_PROBCOPY() got a new parameter `global` to indicate whether the global problem or a local version is copied.
5914
5915### Deleted and changed API methods
5916
5917- implemented SCIPlpiGetPrimalRay() in SoPlex interface that has become available with SoPlex version 1.5.0.2
5918- allowed calling SCIPgetRowSolActivity() in `SCIP_STAGE_SOLVED`, since LP is still available
5919- various extensions and modifications for expressions and expression trees (too much to state here)
5920- The result value `SCIP_NEWROUND` has been added, it allows a separator/constraint handler to start a new separation round
5921 (without previous calls to other separators/conshdlrs).
5922- SCIPcalcNodeselPriority() got a new parameter `branchdir`, which defines the type of branching that was performed: upwards, downwards, or fixed.
5923
5924- Constraint Handlers:
5925 - Method SCIPincludeQuadconsUpgrade() of quadratic constraint handler got new parameter `active` to indicate whether the upgrading method is active by default.
5926 - Method SCIPseparateRelaxedKnapsack() in knapsack constraint handler got new parameter `cutoff`, which is a pointer to store whether a cutoff was found.
5927
5928- Nonlinear expressions, relaxation, and solver interface:
5929 - SCIPcreateNLPSol() now creates a `SCIP_SOL` that is linked to the solution of the current NLP relaxation
5930 - Various types and functions dealing with polynomial expressions have been renamed to use the proper terms `monomial` and
5931 `polynomial` in nonlinear expressions (nlpi/∗expr*); results in many renamings of types, structs and methods.
5932 - The methods SCIPnlpGetObjective(), SCIPnlpGetSolVals(), and SCIPnlpGetVarSolVal() have been removed, use SCIPgetNLPObjval(),
5933 SCIPvarGetNLPSol() and SCIPcreateNLPSol() to retrieve NLP solution values instead.
5934 SCIPcreateNLPSol() now returns an error if NLP or NLP solution is not available
5935 - Removed methods SCIPmarkRequireNLP() and SCIPisNLPRequired(), because the NLP is now always constructed if nonlinearities
5936 are present.
5937 - SCIPgetNLP() has been removed and NLP-methods from pub_nlp.h have been moved to scip.h, which resulted in some renamings, too.
5938 - renamed SCIPexprtreeEvalSol() to SCIPevalExprtreeSol() and now located in scip.h.
5939 - renamed SCIPexprtreeEvalIntLocalBounds() to SCIPevalExprtreeLocalBounds() and now located in scip.h.
5940 - renamed SCIPexprtreeEvalIntGlobalBounds() to SCIPevalExprtreeGlobalBounds() and now located in scip.h.
5941 - The functions SCIPnlpiGetSolution() and SCIPnlpiSetInitialGuess() got additional arguments to get/set dual values.
5942 - The method SCIPgetNLPI() got a new parameter `nlpiproblem`, which is a pointer to store the NLP solver interface problem.
5943
5944- Timing:
5945 - SCIPincludeProp() got additional parameters to set the timing mask of the propagator and the new callbacks and parameters
5946 related to calling the propagator in presolving.
5947 - SCIPincludeConshdlr() got additional parameters to set the variable deletion callback function and the timing mask for
5948 propagation.
5949 - removed parameters timelimit and memorylimit from SCIPapplyRens()
5950 - The parameters `timelimit` and `memorylimit` were removed from SCIPapplyRens().
5951
5952- Problem Data:
5953 - The method SCIPcopyProb() got a new parameter `global` to indicate whether the global problem or a local version is copied.
5954
5955- Writing and Parsing Constraints:
5956 - The methods SCIPwriteVarName(), SCIPwriteVarsList(), and SCIPwriteVarsLinearsum() got a new boolean parameter `type`
5957 that indicates whether the variable type should be written or not.
5958 - The methods SCIPparseVarName() and SCIPparseVarsList() got a new output parameter `endptr` that is filled with the position
5959 where the parsing stopped.
5960 - The method SCIPwriteVarsList() got additionally a new parameter `delimiter` that defines the character which is used for delimitation.
5961
5962- Variables:
5963 - SCIPmarkDoNotMultaggrVar()/SCIPvarMarkDoNotMultaggr() now allow to mark negated and aggregated variables
5964 - SCIPgetVarCopy() got a new parameter `success` that will be FALSE if method is called after problem creation stage and no hash map is
5965 given or no image for the given variable is contained in the given hash map.
5966 - SCIPchgVarType() got an extra boolean parameter to store if infeasibility is recognized while upgrading a variable from continuous
5967 type to an integer type.
5968 - SCIPdelVar() got a new parameter `deleted`, which stores whether the variable was successfully marked to be deleted.
5969
5970### New API functions
5971
5972- information about the quality of the solution of an LP (currently the condition number of the basis matrix) can now be:
5973 + requested from the LPI (currently only available for CPLEX): methods SCIPlpiGetRealSolQuality() and
5974 + SCIPprintLPSolutionQuality() command display lpsolquality in interactive shell display column lpcond to show
5975 + estimate on condition number, if available
5976- SCIPround() and SCIPfeasRound() to round to nearest integer
5977- SCIPsortRealRealIntInt() and corresponding sorting/inserting/deleting methods in pub_misc.h and necessary defines in misc.c
5978- SCIPsortRealIntLong(), SCIPsortPtrPtrRealInt() and corresponding sorting/inserting/deleting methods in
5979 pub_misc.h and necessary defines in misc.c
5980- SCIPcomputeLPRelIntPoint() to compute relative interior point of the current LP
5981- SCIPstartSolvingTime() and SCIPstopSolvingTime() which can be used to start or stop the solving time clock
5982- SCIPstrToRealValue() and SCIPstrCopySection() in pub_misc.h; these methods can be used to convert a string
5983 into a `SCIP_Real` value and to copy a substring.
5984- SCIPgetBinvarRepresentatives() which gets binary variables that are equal to some given binary variables,
5985 and which are either active, fixed, or multi-aggregated, or the negated variables of active, fixed, or multi-aggregated variables
5986- SCIPhasPrimalRay() and SCIPgetPrimalRayVal() that return whether a primal ray is stored and which value a
5987 given variable has in the primal ray, respectively
5988- SCIPsetConsModifiable()
5989- SCIPsetParam() which is a generic parameter setter method, independent of the parameter type
5990- SCIPpropInitpre(), SCIPpropExitpre(), SCIPpropPresol() which initializes, exists and executes the presolving phase
5991- SCIProwGetAge() to access the age of a row (pub_lp.h/lp.c)
5992- SCIPsolGetOrigObj() in pub_sol.h which returns for a solution in the original problem space the objective value
5993- SCIPretransformSol() in scip.h that allows to retransform a solution to the original space
5994- SCIPlpiClearState() to LP interfaces for clearing basis information in the LP solver
5995- SCIPgetSubscipDepth() to access the depth of the current SCIP as a copied subproblem
5996- SCIPdebugAddSolVal() and SCIPdebugGetSolVal() to add/get values to/from a debug solution
5997- SCIPsepastoreRemoveInefficaciousCuts() to remove non-efficious cuts from the separation storage
5998
5999- Nodes:
6000 - SCIPnodeGetParent() to get parent node of a node
6001 - SCIPnodesSharePath() in pub_tree.h that determines whether two nodes are on the same leaf-root path
6002 - SCIPnodesGetCommonAncestor() in pub_tree.h that finds the common ancestor node for two given nodes
6003
6004- Read and Write:
6005 - SCIPgetReadingTime() which returns the time for reading in seconds
6006 - SCIPparseVarsLinearsum(), SCIPparseVarsPolynomial() and SCIPwriteVarsPolynomial() and for writing and
6007 parsing polynomials in constraint handler writing/parsing methods
6008
6009- Memory:
6010 - SCIPcreateMesshdlrPThreads() and SCIPfreeMesshdlrPThreads() for allocating and deleting necessary memory
6011 for message handlers for parallel pthread version
6012 - SCIPallocClearMemoryArray() and BMSallocClearMemoryArray() for allocating cleared memory arrays in scip.h and memory.h
6013
6014- Intervals:
6015 - SCIPintervalPowerScalarInverse() to solve an equation y = x^p for given bounds on y and scalar exponent p
6016 - SCIPintervalQuadBivar() to compute tight bounds on a bivariate quadratic form
6017 - SCIPintervalSolveBivariateQuadExpressionAllScalar() to compute tight bounds on the solutions of a bivariate quadratic equation
6018
6019- Variables:
6020 - SCIPcomputeVarCurrent{L,U}b{Local,Global}() to compute local or global lower or upper bounds of a
6021 multiaggregated variable from the bounds of the aggregation variables
6022 - SCIPbranchVarValNary() for n-ary variable branching
6023 - SCIPgetNegatedVars() which returns all negated variables for a given array of variables, if the negated
6024 variables are not existing yet, they will be created
6025 - SCIPgetNTotalVars() that returns the total number of created vars, icluding variables that were deleted in the meantime
6026 - SCIPvarGetHashkey(), SCIPvarIsHashkeyEq(), SCIPvarGetHashkeyVal() in pub_var.h which can be used for `SCIP_HASHTABLE` of variables
6027 - SCIPvarGetNBdchgInfosLb() and SCIPvarGetNBdchgInfosUb() in pub_var.h returning the number of lower or upper bound changes on the active path
6028 - SCIPvarGetBdchgInfoLb() and SCIPvarGetBdchgInfoUb() returning the bound change information at the given position
6029 - SCIPvarMarkDeletable() to mark a variable to be deletable completely from the problem (for
6030 branch-and-price); can only be called before the variable is added to the problem
6031 - SCIPvarMarkNotDeletable() that marks a variable to be non-deleteable (used within SCIP for forbidding
6032 deletion of variables contained in solution, LP bases, (multi)aggregation, ...)
6033 - SCIPvarIsDeletable() that returns whether a variable is marked to be deletable (each variable is per default non-deletable)
6034
6035- NLP:
6036 - SCIPgetNLPVarsNonlinearity() to get for each variable in the NLP the number of NLP rows in which this variable appears in a nonlinear way
6037 - SCIPnlrowGetDualsol(), SCIPgetNLPVarsLbDualsol(), SCIPgetNLPVarsUbDualsol() to retrieve dual values from an NLP solution
6038 - SCIPgetNLPFracVars() to get the fractional variables in an NLP solution
6039
6040- Propagator:
6041 - SCIPpropSetPresolPriority() which changes the presolving priority of a given propagator