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The "D" solvers (GAMS/ConoptD, GAMS/ConvertD, GAMS/CplexD and GAMS/LGOD)

The “D” solvers GAMS/ConoptD, GAMS/ConvertD, GAMS/CplexD and GAMS/LGOD started as research and development versions of the production solvers GAMS/Conopt, GAMS/Convert, GAMS/Cplex and GAMS/LGO. So these “D” solvers offer some interesting new features that eventually will migrate into the production version. As of distribution 23.6 all new features of GAMS/ConoptD and GAMS/LGOD have been migrated to the production version and both GAMS/ConoptD and GAMS/LGOD are merely an alias for GAMS/Conopt and GAMS/LGO. We generally recommend to work with the production version of the solver and only cautiously use the “D” version if the new feature is essential to the model. Backward compatibility is of great concern to us, but with the “D” solvers, the backward compatibility requirements are relaxed (e.g. the ConoptD solver will soon disappear from the list of solvers).

The following describes the differences between the research and development “D” solvers and the production version as of distribution 24.0.

Convert and ConvertD

The ConvertD “solver” lacks most Convert options. The only Convert options implemented in ConvertD are:

  • Analyze: Generates three text files for rows columns and matrix
  • AnalyzeS: Generates short form of Analyze
  • Baron: Generates Baron input file
  • CplexMPS: Generate CPLEX MPS format input file
  • Dict: Generate Convert to GAMS Dictionary
  • FixedMPS: Generate fixed format MPS file
  • Gams: Generate GAMS scalar model. This is the default conversion format used.
  • Jacobian: Writes GDX version of current point - Jacobian
  • OSiL: Generates Optimization Services instance Language (OSil) file

The former Convert option Hessian is now only available in ConvertD and the Jacobian option has additional information. Moreover a few options are exclusively available in ConvertD:

  • LocalSolver: Generate LocalSolver input file
  • DictMap: Generate Convert to GAMS Dictionary Map

Moreover, in-core model communication (Solvelink=%Solvelink.LoadLibrary%) is supported by ConvertD only.

GAMS/CplexD versus GAMS/Cplex

Similar to Convert/ConvertD, the CplexD link to Cplex lacks a lot of functionality. For example, sensitivity analysis and support for SOS variables are absent from the CplexD link. But CplexD offers a few facilities of interest to a small community:

  1. Handles quadratically constraint models better than the production link. Some SOCP models are reformulated in the production link so that Cplex rejects these models while CplexD solves them nicely. Moreover, CplexD provides duals for this problem type.
  2. Provides 'hot start' capability in GUSS/Scenario Solver
  3. Allows solving multiple instances of GAMSModelInstance in parallel using the object oriented GAMS API
  4. Is capable of Solvelink=%solvelink.AsyncThreads%
  5. Cplex Remote Object
  6. Cplex distributed MIP
  7. Provides the correct value of the objective variable in the 'userincbicall'
  8. Provides access to Cplex Benders' decomposition
solver/the_d_solvers_gams_conoptd_gams_convertd_and_gams_cplexd.txt · Last modified: 2017/05/05 08:26 by admin