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) 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.