COPT Changelog#

20260610#

  • Fixed a bug causing NLP initial guess to be submitted only when a dual initial guess was available.

  • Fixed input of LP basis (which helps accelerate resolve).

  • Option tech:writesolution to export .bas, .iis, .sol files.

20260609#

  • Fixed a bug in the interface for the local solver where parts of expressions and objective function could be lost.

  • Use initial guess in NLP.

  • Added various solution statuses, in particular locally optimal and locally infeasible for NLP.

  • Added option alg:qmatrixtol.

  • Updated to COPT 8.0.5, with performance improvements and bug fixes.

20260414#

  • Option alg:nonconvex, mip:startmode.

  • Fixed objective value output.

  • Fixed objective suffixes (.objpriority etc, see option obj:multi).

  • Changes in MP, in particular:

    • Option cvt:pre:boundsbest defaults to making auxiliary subexpression result variables free, unless the result is constant. This allows stronger nonlinear presolve.

20260322#

  • Updated to COPT 8.0.3, with performance improvements and bug fixes

  • Added option lp:concurrentmode

  • Added support for conic constraints

  • Added support for many non-linear expressions

  • Added native multi-objective optimization

20260108#

  • Updated to COPT 8.0.2, that introduces a global nonconvex (MI)QCQP solver and performance improvements.

  • Added options tech:loglevel, mip:prerootheurlevel, mip:repair

20251210#

  • Option obj:multi:options: fix integer-valued objective-specific options.

20251121#

  • New option obj:multi:options to control whether multi-objective option suffixes are used.

20251021#

  • Changes in MP: option cvt:expr:nlassign.

  • Upgrade to COPT 7.2.11.

  • Enable NLP (set options acc:_expr=2 alg:relax=1).

20251015#

  • Changes in MP

20250814#

  • Changes in MP

    • Improved preprocessing of logical and combinatorial expressions (options cvt:pre:unnest, cvt:pre:sort).

    • Option cvt:pre:boundlogarg (default 0) to bound arguments of logarithm nonnegative. Previously always done, sometimes deteriorating performance of nonlinear solvers.

20250801#

  • Changes in MP

    • Tolerances set by options pre:feastol, pre:feastolrel both need to be violated to produce a warning on contradicting variable/constraint bounds. Previously the preprocessor failed on any violation, without letting the solver try.

    • Options cvt:compl, cvt:compl:eps control complementarity reformulations.

20250617#

  • Changes in MP

    • Multi-objective emulator: added support for objective-specific options via objective suffixes beginning with option_

    • Option cvt:unnest: bits 2 and 4 switch on inlining of linear and quadratic subexpressions produced during reformulations (by default on).

    • Options cvt:pre:ctx2ineq, cvt:pre:ctx2count to control context propagation into conditional comparisons #267.

  • Enable native indicator constraints by default (options acc:ind..)

20250429#

  • Fix a bug in parsing of quadratic expressions, which could wrongly parse products of unequal linear expressions, such as (x-3)*(x-z-5).

20250424#

  • Changes in MP

    • Option cvt:qp2pass (default even faster parsing of quadratics)

20250408#

  • Fixed a bug in parsing of quadratic expressions

20250407#

  • Updated to COPT version 7.2.6

  • GPU is now supported for PDLP on Windows and Linux; CUDA library version >= 11.7 is required. See options lp:method and lp:pdlpgpumode.

20250329#

  • Changes in MP:

    • Option cvt:multoutcard to limit the size of out-multiplied QP expressions. Can improve speed on large models.

    • Improved parsing of quadratic expressions.

20250308#

  • Option mip:gapabs

20241228#

  • Updated to COPT 7.2.4, which includes performance improvements to the MIP, SOCP and QCQP solvers

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

20240531#

  • Updated to Copt 7.1.3, which provides many bugfixes.

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.

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.

20240410#

  • Updated to Copt 7.1.1, with support for first-order method (PDLP). On Windows this can be used with GPU supporting CUDA. It can be controlled setting lp:method to the new value 6 (PDLP) and with options lp:pdlpgpumode, lp:pdlpgpudevice and lp:pdlptol

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 MP linearization.)

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

  • Option report_times

  • Unused acc: options.

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

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.

20231117#

  • Updated to Copt 7.0.3, which includes many performance improvements

  • New keyword lim:soltime to specify a time limit after a solution has been found

  • 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.

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.

20230726#

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

20230724#

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

20230621#

  • Fix quadratic objective with repeated subexpressions.

20230616#

  • Changes in MP.

20230428#

  • Updated to Copt 6.5.2, which includes performance improvements and fixes for issues with MIP problems

20230424#

  • Changes in the MP library: added variable names support and removed spurious starting solution

20230330#

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

20230207#

  • Changes in the MP library

  • Updated to Copt 6.0.4, which includes bugfixes

  • Added support for unbounded/Farkas rays calculation

20221228#

  • Changes in MP

20221222#

  • 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.

20230207#

  • Updated to Copt 6.0.1, which includes: many performance improvements native support for quadratic constraints

20221012#

  • Piecewise-linear approximation of quadratics For non-convex quadratics, set the following options: cvt:quadobj=0 and/or cvt:quadcon=0.

20220928#

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

20220715#

  • Updated to Copt 5.0.1, which includes many performance improvements

  • Added feasibility relaxation (see alg:feasrelax)

  • New parameters: alg:iismethod

20220615#

  • New parameter: crossover

  • Minor changes to parmeter names

20220526#

  • SOS constraints are now detected also if the .ref suffix is integer

  • Minor changes to parmeter names

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) COPT does not support quadratic range constraints. Conversion of linear range constraints into one-side rhs constraints has been generalized for any algebraic ones.

20220411#

  • First mp-based release, linked with COPT libraries 4.0.5