GUROBI Changelog

20240808

  • Added option alg:nlpheur to control an heuristic for non-convex quadratic models.

20240728

  • Updated to Gurobi libraries 11.0.3, which include many bug fixes.

20240724

  • Option acc:_all

    • Useful to disable all reformulations (acc:_all=2), or force linearization (acc:_all=0).

  • Option cvt:prod

    • Controls reformulation of binary products into logical constraints.

  • Faster input of quadratic expressions.

20240617

  • Multi-objective emulator

    • obj:multi=2 forces emulation, even if MO natively supported.

    • Fixed a bug in the objective degradation suffixes .objasbtol, .objreltol.

20240604

  • Presolve division by constant, resulting in fewer constraints.

  • Fix no-solution case in multi-objective emulator.

20240529

  • Multi-objective emulator

    • All flat MP solvers support multi-objective mode (obj:multi=1), either natively, or via emulation.

    • Suffixes .objpriority, .objweight, .objabstol, .objreltol.

    • [BREAKING] Default intuitive handling of .objweight, see option obj:multi:weight, even when natively supported.

20240518

  • Updated to Gurobi libraries 11.0.2, which include many bug fixes.

20240429

  • [BREAKING] Merged report_times and timing; they are now aliases, set the value to 1 to have basic info, to 2 to have more detailed info.

20240327

  • Added support for Web License Server parameters, via options wls_licenseid, wls_accessid, wls_secret, wls_token, wls_tokenduration and wls_tokenrefresh.

20240320

  • SOS constraints.

    • Fixed handling of SOS2 constraints created by AMPL as reformulations of PL expressions (option pl_linearize 1, default; set to 0 to use the solver’s native PL functions or MP linearization.)

    • Disallow repeated weights for SOS constraints (suffixes .sosno/.ref.)

  • Native handling of POW(x, INT).

    • Power expressions with positive integer exponent are passed natively vs previously quadratic or linear reformulation. For best performance, global solving capability might be needed (global=1).

  • Option report_times

  • Unused acc: options.

    • The constraint acceptance options acc:... for non-handled constraints are ignored (previously triggered error.)

20240311

  • Added option tech:reportwork to display or return in the problem suffix work the work units spent while solving the problem.

20240310

  • Updated to Gurobi libraries 11.0.1, which include many bug fixes.

20240115

  • Solve result codes

    • List codes by running (solver) -!

    • [BREAKING] Standardized codes. Major changes:

      • 100-199 (solved?) means solution candidate provided, but can be suboptimal/infeasible

      • 300-349 means unbounded problem but feasible solution returned

      • 400-449 means limit/interrupt but feasible

    • [BREAKING] sol:chk:fail returns code 150 (solved?)

  • Improved translation of SOCP constraints.

    • Options cvt:socp, cvt:socp2qc.

  • Compact solution check warnings

  • Fixed presolve of the power function #226.

20231208

  • Option global and suffix .global synonyms for funcnonlinear

  • Changed values for global / funcnonlinear options and suffixes: default 0 (Gurobi automatic), -1 (static PL approximation), 1 (global solving).

20231206

  • Updated to Gurobi 11

    • Non-linear models can now be solved using spatial branch-and-bound and outer approximation instead of piecewise linearizattion. To use this set the option pre:funcnonlinear to 1 and the suffix funcnonlinear to -1

    • Added keywords cut:mixingcuts, alg:concurrentmethod and alg:solutiontarget

20231117

  • Added option lim:work (worklimit).

  • MP update: fixed graceful exit on Ctrl-C from AMPL in Linux and fixed issue with reading text-format NL files

20231103

  • Improved translation of logical constraints: inlining of nested disjunctions and conjunctions; fewer auxiliary binary variables.

20231017

  • Fixed a bug in NL reader on Windows.

20230920

  • Updated to Gurobi libraries 10.0.3, which include many bugfixes.

20230919

  • mp_options. Receive mp_options from AMPL (for all MP solvers). They are parsed before (solvername)_options.

  • Solution checking: relative tolerance sol:chk:feastolrel; options sol:chk:round, sol:chk:prec.

20230831

  • Solution checking, options sol:chk:* (experimental).

  • Preprocess And/Or constraints.

20230817

  • Alternative solutions: solve status equal to that of the final solution.

  • Fixed a bug causing repeated names for auxiliary variables and constraints.

  • Option values can be assigned without ‘=’.

  • Fixed a bug where equivalent conditional comparisons were not unified.

20230728

  • Option ‘tech:writesolution’ #218

  • Option ‘writeprob’ (‘tech:writemodel’) ASL-compatible

20230726

  • Fixed inequalities of integer expressions with non-integer constants, see test_int_non_int.mod.

  • Option ‘writesol=filename’ to export solutions/results.

20230724

  • Option [solver_]auxfiles rc; transfers names of variables and constraints into the model; (solver)_options ‘cvt:names=0-3’ controls names.

20230625

  • Updated to Gurobi libraries 10.0.2, which include many bugfixes.

20230621

  • Fix quadratic objective with repeated subexpressions.

20230616

  • Changes in MP.

20230531

  • Wrong solver options are gracefully reported via solve_message.

20230522

  • Added option ‘lim:sol’ to set a limit on the number of solutions found

20230426

  • Fixed partial MIP start.

20230330

  • Fixed the outlev option.

20230321

  • Recognition of second-order conic constraints from algebraic representations and conversion into quadratic constraints; Gurobi appears to recognize second-order cones from quadratics.

20230207

  • Changes in the MP library.

20230206

  • Relinked with Gurobi version 10.0.1, which includes many bugfixes

  • Changed behaviour of ‘tech:logfile’, which no longer implies ‘tech:outlev=1’. Specifying a logfile will enable gurobi’s full log to file only; to obtain both console and log output, set also ‘tech:outlev=1’.

20221228

  • Changes in MP

20221222

  • Fixed #195: shorter error message for missing NonConvex=2 option

  • Bug fixes in MP

20221211

  • Changes in MP: added the ==> else operator Implemented implication with ‘else’: constr1 ==> constr2 [else constr3]

  • Changes in MP: PLApproxRelTol, PLApproxDomain Parameters to control piecewise-linear approximation. cvt:plapprox:reltol default value changed from 1e-5 to 0.01.

20221113

  • Gurobi 10.0 support Options ‘lim:mem’, ‘lim:softmem’, ‘mip:obbt’ and ‘alg:networkalg’ Added option tech:writepresolvedprob to export the presolved model

  • Released the new MP-based Gurobi driver The new driver becomes the default (and is named just ‘gurobi’)

20221012

  • Piecewise-linear approximation of quadratics For Gurobi, non-default. To use, set the options cvt:quadobj=0 cvt:quadcon=0. Recognizing x^2 for stronger univariate approximation

20220928

  • Changes in MP: piecewise-linear approximations of nonlinear functions, default value of big-M

  • For range constraints x-gurobi reports nonbasic status low/upp, for one-sided constraints low/upp/equ, consistent with ASL drivers

  • Sensitivity analysis: use constraint suffixes .sens(lb/ub)(lo/hi), the old-style suffixes .sensrhs(lo/hi) meaningful only for one-sided constraints.

  • Suffixes .iis(lb/ub)force on constraints and variables

20220802

  • Added support for ‘params’ option from command line and environment variable

20220725

  • Changes in MP fixed suffixes export on Windows and multiple solutions handling

20220720

  • Options ‘funcpieces’, ‘funcpiecelength’, ‘funcpieceratio’, ‘funcpieceerror’ The above options (and corresponding suffixes) are passed to Gurobi. The suffixes can specialize the values for individual constraints.

    Subexpressions: note that if a subexpression is contained in several constraints, for contradicting suffix values the maximum is taken.

20220706

  • Relinked with Gurobi 9.5.2, which contains bug fixes

20220511

  • Complementarity constraints: also quadratics Complementarity constraints now handle quadratics.

  • Branch develop is used for new code The active development branch is now develop.

  • Convert quadratic range constraints to QuadCon(LE/EQ/GE) Gurobi does not support quadratic range constraints. Conversion of linear range constraints into one-side rhs constraints has been generalized for any algebraic ones.

20220408

  • Linear complementarity in MP: 1st go

  • Other changes in MP

20220303

  • Fix strict comparison tolerance Option cvt:mip:eps, default 1e-3.

20220217

  • Assume new constraints are active (#152): Gurobi requires a complete basis for hotstart and we have to guess the statuses of new variables and constraints.

  • Allowing SOS constraints with repeated weights (#163): Although Gurobi states SOS weights should be unique, it accepts them repeated. This happens when AMPL linearizes a PL function with redundant (repeated) slopes. It seems better to use PL functions natively (option pl_linearize 0;).

  • Native handling of abs, min/max, and/or, and indicators by default: For the general constraints abs, min/max, and/or, Gurobi 9.5 seems to use tight MIP reformulations, matching the performance of MIPConverter redfinitions. In contrast, indicator constraints behave differently to MIP reformulations (accessible by acc:ind_..=1): better primal and worse dual bounds. Setting acc:* = 2 as default (native handling).

20220202

  • Basis status low/upp/sup for new variables: when new variables are added, AMPL assigns .sstatus none while Gurobi 9.5 needs a complete basis so we automatically set Gurobi var status to low/upp/sup depending on where 0.0 is relative to the bounds.

20220128

  • First eXperimental release, linked with Gurobi 9.5.

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