25.0 Distribution

# 25.0.1 Major release (January 17, 2018)

## 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 Wolfgang Britz, Jeff Dischler, Michael Ferris, Dhruv Gupta, Erwin Kalvelagen, Florian Landis, Andre Lemelin, Erfan Mohagheghi, Anthony Paul, and Nathan Sudermann-Merx.

## Platforms

• Due to the discontinuation of Cplex on Windows 32bit (with Cplex 12.7 in 2016) we are faced with potentially phasing out/dropping solvers depending on Cplex on Windows 32bit with the next major release. The most likely candidate for this is ANTIGONE. These solvers will still be available for 64-bit Windows and other supported platforms. Other solver vendors (e.g. Gurobi and FICO-Xpress) have also announced the discontinuation of their product on the Windows 32bit platform. If you rely heavily on the availability and support of the Windows 32bit platform please contact suppo.nosp@m.rt@g.nosp@m.ams.c.nosp@m.om to discuss your options.
• As announced, dropped support for x86-64 Solaris.
• As announced, increased the minimal required MacOS X version to 10.11.
• As announced, increased the minimal required GLIBC version on Linux to 2.12.

## GAMS System

### GAMS

• Extended the $offEmbeddedCode facility to allow the use of a "projection operator": $offEmbeddedCode {symbol[<[=]embSymbol[.dimX]]}
• Added support for the Object-oriented GAMS Python API in the Embedded Code Facility for Python. The method gams.set() accepts instances of type GamsParameter, GamsSet, etc. as data. Instances of GamsWorkspace and GamsDatabase can be retrieved using the properties gams.ws and gams.db. The property gams.wsWorkingDir can be used to specify the working directory of the created GamsWorkspace.

## Solvers

### BONMIN(H), CBC, Couenne

• Branch-and-bound now checks wallclock-time, if running with multiple threads.

### CONOPT4

• New libraries 4.05.
• Improved the selection of post-triangular variables when there are multiple candidates.

### CPLEX

• Bugfix: If the Cplex conflict refiner (triggered by option iis) could not identify a conflict the behavior was erratic. This has been fixed.
• Bugfix: Value 6 for option MIPStart was documented but got rejected. This has been fixed.

### DICOPT

• Fixed setup of NLP projection problem in feasibility pump.
• Fixed stopping criterion when using stop on crossover: DICOPT was stopping as soon as the relative gap between the objective value of the best known solution and the bound provided by the MIP relaxation was below 0.001, thus might have declared suboptimal solutions as optimal. With this release, DICOPT will use the value of GAMS option optcr as optimality tolerance. Note, that the default for this option is 0.1 (!).

### Ipopt(H)

• New libraries.

### MOSEK

• No update, but be aware that Mosek announced to drop the convex nonlinear optimizer in their next major release (Mosek 9). Thus, in a future GAMS release, GAMS/Mosek will not accept models with model types NLP or DNLP anymore. Note, that linear or quadratic problems (LP, MIP, (MI)QCP) are not affected.

### SCIP

• New libraries 5.0.1 (227c4c7).
• New option presolving/symmetry/displaynorbitvars.

### SoPlex

• New libraries 3.1.1 (ab921a5).

## Tools

### MODEL2TEX

• Added support for singleton sets.
• Fixed a dependency bug on Mac OS X which prevented model2tex from working.
• Fixed a bug regarding SOS variables.
• Fixed a bug regarding domain jumps.
• Added support for Python 3 on Linux and Mac OS X.
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