GUROBI Changelog


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


  • 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.


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

  • Preprocess And/Or constraints.


  • 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.


  • Option ‘tech:writesolution’ #218

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


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

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


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


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


  • Fix quadratic objective with repeated subexpressions.


  • Changes in MP.


  • Wrong solver options are gracefully reported via solve_message.


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


  • Fixed partial MIP start.


  • Fixed the outlev option.


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


  • Changes in the MP library.


  • 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’.


  • Changes in MP


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

  • Bug fixes in MP


  • 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.


  • 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’)


  • 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


  • 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


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


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


  • 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.


  • Relinked with Gurobi 9.5.2, which contains bug fixes


  • 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.


  • Linear complementarity in MP: 1st go

  • Other changes in MP


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


  • 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).


  • 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.


  • First eXperimental release, linked with Gurobi 9.5.