22.8.1 Major release (August 01, 2008)

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, Andrea Consiglio, Anton Eremeev, Mustafa Esen,Josef Kallrath, Erwin Kalvelagen, Todd Munson, Rich Roberts, and Andres Ramos.

• GAMS scratch file extension: Starting with distribution 22.9 the default file extension of intermediate files located in the 225? directories will change from .scr to .dat. For distribution 22.8 it is still .scr. The scratch extension now is a parameter that can be changed with the GAMS option ScrExt, e.g gams trnsport scrext=tmp. Within GAMS code you get the scratch extension using %gams.scrext%.
• Increased the maximum input line length to 40,000 characters and the maximum number of columns in a table to 10,000.
• Checking for an interrupt is now also done inside a GAMS looping constructs.
• The $LOAD directive can read the universe from a gdx file by specifying $LOAD id=*.
• Certain gdx file read operations are now faster and use less memory.
• GAMS parameters gdxcompress and gdxconvert
  • Allow new gdx files to be written in an older format of the gdx file.
  • Usage through an environment variables (valid for all gdx related operations): gdxconvert = <value> and gdxcompress = <value> or via GAMS command line parameters: gdxconvert = <value> and gdxcompress = <value>.
  • Possible values for gdxcompress
    • 0 (or empty): no compression
    • 1: compression turned on
  • Possible values for gdxconvert:
    • V7: version 7
    • V6: version 6
    • V5: version 5
  • E. g. to get a compressed v6 gdx file enter: gams <model_name> gdxconvert=v6 gdxcompress=1 gdx=<gdx_file>.
  • Note:
    • With GAMS 22.8 the default format for gdx files is V7 uncompressed.
    • Only V6 and V7 support compression.
    • V7 formatted files were introduced with version 22.6 of GAMS; V6 formatted files were introduced with version 22.3 of GAMS. GAMS platforms that were introduced after 22.3/22.6 (e.g. Mac Intel or SunSparc64) do not support V5/V6.
    • The command line options have a higher precedence as the environment variables with the same name.

• New
  • gdx2xls: Converts an entire gdx data container to a Microsoft Excel spread sheet.
  • invert: Calculates the inverse of a matrix provided as a gdx file (for more information see gdxutils documentation).
  • msappavail: Checks which Microsoft Office programs are installed.
  • xlstalk: Allows some interaction with Excel to open/close/save Excel files.
• Extended/Updated
  • gdxcopy: New option to replace existing gdx files.
  • gdxdiff New id option to compare specified ids only.
  • gdxmerge New optional output parameter to specify the name of the output file.
  • gdxviewer: Fixed problem with cube view.

Fixed problem when moving a column to the plane in the gdx data viewer.

New models, including tests for

• invert utility
• ls solver
• poly function
• gdxconvert and gdxcompress parameters

GAMS introduces the new model library 'GAMS Data Utilities' containing models that demonstrate the various utilities to interface GAMS with other applications.

The models of the forthcoming book PRACTICAL FINANCIAL OPTIMIZATION - A Library of GAMS Models by Andrea Coniglio, Soren Nielsen, and Stavros A. Zenios have been included in the GAMS distribution. It is a companion volume to the book Practical Financial Optimization by Stavros A. Zenios.

New libraries 8.1.5 for Windows, Linux, and AIX

GAMS 22.8 introduces a third experimental solver BDMLPD besides CONOPTD and CPLEXD. They are very similar compared to their professional brothers BDMLP, CONOPT and CPLEX. They lack some functionality (e.g. CPLEXD does not solve QCP models) but offer in-core communication between GAMS and the solver. No large model scratch files need to be written to disk which can save time if you solve many models in your GAMS program. This in-core execution is activated by setting <modelname>.solvelink=5; before the solve statement.

• CoinBonmin
  • New libraries 0.99
  • Support of user-defined cut generators and heuristics via BCH (Branch and Cut Heuristic)
• CoinCbc new libraries 2.1
• CoinScip supports user-defined cut generators, heuristics, and incumbent report callbacks via BCH

New option hessian to dump the Hessian matrix into a GDX file. Similar to the option jacobian.

New libraries 11.1.1

New libraries 5.0.1.292. Sun Sparc Solaris 5.0.1.274.

Linear Least Squares Solver

New libraries 5 Rev 90

New libraries for Windows