20.3 Major release (December 24, 2001)

Table of Contents

GAMS System

GAMS

  • Restrictions of number of symbols, set elements and execution code size have been completely removed.
  • Performance enhancements for very large models with millions of rows and columns.
  • Minor language enhancements: $on/offecho copies a block of lines to a file. The text is subject to string macro processing as well as inline and eol comment removal. For example: 
           $onecho > myfile
       ...
       $offecho
  • To append to a file use ">>".

IDE

  • Contributed solver installation files (e.g. QPWRAP, DEA, ... see [User Contributed Software and Tools] (https://forum.gams.com/tag/contributed-documentation)) can now be installed using the IDE. Place the installation file (file extension *.zip or *.pck) in the GAMS system directory and click on the "Update" button in File->Options->Execute

Solvers

Uniform Solver Naming Conventions

  • Since solvers are distributed with past, production, and beta versions (e.g. OSL, CONOPT, ...) a consistent naming convention has been adoped.
  • The following simple rules apply:
    1. The base name of the solver does not change (e.g. CPLEX, OSL, CONOPT, ...) and refers to the current production version.
    2. Past and beta versions have names derived from the base name. For example, in this release we distribute CONOPT1 (past), CONOPT2 (production), and CONOPT3 (future). The base name CONOPT refers to CONOPT2.
  • If you select the base name of a solver from now on you will get the most recent production version of the solver. For the following solvers the naming convention has changed:
    New Name (20.3-) Old Name (-20.2)
    CONOPT or CONOPT2 CONOPT2
    CONOPT3 CONOPT3
    CONOPT1 CONOPT
    OSL or OSL2 OSL2
    OSL3 OSL3
    OSL1 OSL
    MINOS or MINOS55 MINOS
    MINOS5 MINOS5
    PATH or PATHC PATHC
    PATHOLD PATH
    MILES or MILESE MILESE
    MILESOLD MILES

CONOPT

  • The future version CONOPT3 is also available on Linux.

CONVERT

  • For BARON and AMPL output GAMS/CONVERT eleminates the objective variable and uses a "true" objective function.

SBB

  • NLP solvers sometimes have difficulties solving particular nodes and using up all the resources in this node. SBB provides options (see subres, subiter) to overcome these instances, but options have to be set in advance. Now, SBB keeps track of how much time is spend in the nodes, builds an average over time, and automatically controls the time spend in each node. The option avgresmult allows the user to customize this new feature.

XPRESS

The XPRESS licensing for Windows, Linux, and Solaris is now much simplified; there is no XPRESS-specific licensing procedure for the user to follow. The GAMS/XPRESS solver takes care of licensing the XPRESS DLL, and does this automatically. Of course, as with other solvers, the GAMS/XPRESS must be licensed with your GAMS system.