53 Distribution

Table of Contents

New Features & Highlights

GAMS Studio

Select GAMS installation

It is now possible to select the GAMS installation to be used in GAMS Studio. There are two ways to set the path to GAMS:

  1. Using the command line parameter --gams-dir.
  2. In the Settings on the General page.

In both cases the path is stored in the GAMS Studio settings and used for the next start.

Studio System Directory

Quick Find and Replace

GAMS Studio now has a quick find option that is available with Ctrl+F in all text views. It uses F3 / Shift + F3 to find next / previous. It is bound to the current tab and changes its focus when switching to another tab. With Ctrl+R it additionally opens the replace section when the current editor isn't readonly.

The known complex search is still available with Shift+Ctrl+F and allows to search forward (F4) and backward (Shift+F4) in parallel independently from quick find.

Studio Find

Solvers

The newest major release of the SCIP Optimization Suite [96] has arrived in GAMS. From the many changes in SCIP 10, we highlight here three points that may be particularly interesting to GAMS/SCIP users:

  1. When solving NLPs or MINLPs, SCIP may call out to a local NLP solver to accelerate the search for a feasible solution. So far, the only NLP solver available in GAMS/SCIP was the high-performance interior point solver Ipopt. While usually a good choice, there can be instances where an active-set based method that can be warm-started is more efficient. Therefore, GAMS has contributed an interface to its solver CONOPT for SCIP version 10. For users with a GAMS/CONOPT license, GAMS/SCIP will now default to use CONOPT as NLP solver. Of course, the option to use Ipopt as NLP solver is still there and is not going away. To instruct GAMS/SCIP to use Ipopt, set parameter nlpi/ipopt/priority to 3000.
  2. SCIP has included a framework for Benders' Decomposition since version 6 (2018). We had not documented this for GAMS/SCIP, because solution values could be obtained for the variables of the master problem only so far. For version 10, GAMS contributed a new relaxator plugin to SCIP, which applies the decomposition on a copy of the problem and allows to retrieve solution values for all master and subproblem variables. To make use of Benders' Decomposition, decomposition information in form of the .stage attribute of variables (1 for the master variables, higher values for subproblems) needs to be provided and parameter decomposition/applybenders needs to be set to TRUE. Note that SCIP's Benders' Decomposition can only work efficiently when subproblems are continuous and recognized to be convex. The use of non-convex subproblems is still possible when all linking variables are of binary type, but may be inefficient.
  3. SCIP has gained the ability to compute irreducible infeasible subsets (IIS) of constraints of an infeasible problem, that is, a subset of constraints that cannot be satisfied, but that is feasible if any of the constraints in the IIS is dropped. IIS has proven to be a valuable tool when analyzing the infeasibility of a model instance and is available with many solvers. For SCIP, the computation of an IIS can be triggered by setting parameter gams/iis to 1 or 2.

53.0.0 Beta release (February 02, 2026)

Acknowledgments

We would like to thank all of our users who have reported problems and made suggestions for improving this release. In particular, we thank Erling D. Anderson, Paul Buckland, Christophe Gouel, and Bruce McCarl.

GAMS System

GAMS

  • Improved performance of the execution backend connection to GAMSPy by caching option definitions.
  • Improved error reporting for $gdxLoadAll to write more information to the lst file.
  • Fixed calculation of maintenance expiration date.

GAMS Connect

Solvers

  • The solve trace feature of some solver links has been extended to write an additional record with I identifier when an improving feasible solution has been found. These lines are enabled by default, and their appearance can be controlled via a solver link option solvetraceincumbent or miptraceincumbent for AlphaECP, CBC, COPT, CPLEX, GUROBI, HiGHS, SBB, SCIP, and XPRESS. The option specifies the minimal absolute change in the primal bound to trigger writing the I line and is set to 10-6 by default.

CPLEX

EXAMINER

  • Updated the tracefile writing facility to be more robust and flexible.
  • Polished the output in many small ways.
  • The hidden solver Examiner2 will be removed in a future release.

GUROBI

  • New libraries 13.0.1.
  • Fixed option freegamsmodel.
  • Fixed option concurrentmethod.
  • Fixed model status in case of an infeasible model with no solution.

HiGHS

  • Added support for CUDA 13 for running cuPDLP-C on GPUs.

KNITRO

  • New libraries 15.1.0.
    • Performance improvements when using the Augmented Lagrangian (AL) algorithm (nlp_algorithm = 6).
    • New option presolveop_clique_merging: Determine whether or not to enable the Knitro presolve operations that attempt to merge cliques to strengthen the formulation.
    • New option presolveop_probing: Determine whether or not to enable the Knitro presolve operations that analyze deductions made by fixing integer variables.
    • New option mip_heuristic_fixpropagate: Specifies whether or not to enable the MIP fix-and-propagate heuristic.
    • New option writeprob: Writes problem to file (format based on extension).
    • Changed default of option ftol to 1e-12.

LINDO/LINDOGLOBAL

  • New libraries 16.0.110.
    • Faster Linear Solver:
      • Simplex solvers solve large linear models an average of 25-30% faster.
    • Integer Solvers Improvements:
      • New heuristics help find good quality solutions for previously unsolvable instances.
      • An average of 15-20% faster to optimality due to enhancements in re-optimizations and 20% more instances solved to optimality on Lindo's standard benchmark suite.
    • Nonlinear and Global Solver Enhancements:
      • Superior performance on difficult nonlinear problems due to improved recovery strategies.
      • Improved Multi-Start solver based on entropy maximization.
      • Improved linearization process and recognition of common terms.
      • Tighter linear relaxations by incorporation of variable bounds.
      • Global solver solution path repeatability improved.

MOSEK

  • New libraries 11.1.3.
    • Updated automatic choice of number of threads to not use more than 32 threads.
    • Reduced memory consumption of graph partitioning based ordering method of the interior-point optimizer when employing more than 8 threads.
  • When solving a mixed-integer problem with all discrete variables fixed (solvefinal), the right-hand-sides of all linear equations and variable bounds are now adjusted such that the solution of the mixed-integer problem satisfies all linear constraints, independent of feasibility tolerances. This increases the chance that the fixed problem can be solved successfully.

NLPEC

  • Fix a failure in case of refType set to "median" and a doubly-bounded variable whose upper bound is negative.

SCIP Optimization Suite

XPRESS

Tools

GAMS Studio

  • New version 1.24.0:
    • New Feature: Added a quick-find to the bottom of text editors for searching in the current file, called "find".
      • The quick "find" is evoked with Ctrl + F and uses F3 / Shift + F3 to find next / previous.
      • The complex "search" dialog is now evoked with Ctrl + Shift + F and uses F4 / Shift + F4 to search next / previous.
    • Added GAMS system directory configuration to settings dialog to switch between different GAMS installations.
    • Translate UNC path to a local path for the license dialog, e.g., when the Documents folder on Windows has been moved to a server.
    • More search improvements:
      • Improved search and replace dialog selection behavior. Now the result selection is removed when the dialog is closed and no search result list is open.
      • Improved search and replace file pattern, i.e., the default pattern has been changed from * to *.gms. The change is applied to all the cases where a file pattern can be configured.
    • Ensure listing files are closed on the file system when the corresponding tab is closed.
    • Improved behavior of --integrated-help=on/off command line option, to ensure the Help View is not unexpectedly disabled when started.
    • Show the LST line number in debug mode when the execution is paused. The information is visible at the very bottom of the debugger.
    • Changed the start directory of the file open dialog to the base directory of the current project.
    • Fixed the path to the main file when running MIRO. Before, the main file path always corresponded to the working directory.
    • Fixed enabling of MIRO menu. Before, the MIRO menu was not enabled in some cases although a correct path has been configured.
    • Fixed wildcard matching for the Model Library dialog, i.e., when wildcard matching was enabled not all models matching the pattern were listed.

MPS2GMS

  • Removed support for creating =c= equations.

APIs

GDX

  • New libraries 7.11.19.
    • Extended and updated internal runtime library for use in other GAMS products.
    • Cleanup and minor touch-ups in GDX object module.

GMO

  • Previously, setting gmoUseQ true for linear models was not supported: several functions in the GMO API would treat this case as a fatal error or would behave in an undefined way. This has been adjusted: now reasonable outputs are efficiently provided in this case.

GAMS Transfer Python

  • Performance related enhancement when validating symbol order in a Container.
  • Added support for pandas 3.0.0.

Model Libraries

GAMS Test Library