23.3.1 Major release (November 01, 2009)

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, Wietse Dol, Daniel T. Fokum, Nuri Gokhan, Iiro Harjunkoski, Josef Kallrath, Lloyd R. Kelly, Kristina Konold, and Uwe Schneider.

GAMS System

GAMS

Assigning members to a set using the asterisk is now possible in decreasing order as well. For example, the following are valid set statements in GAMS.
```
  Set years /bc2000*bc1,0*2009/;
  Set years /"-20"*"-1"/;
```
The GAMS parameters ProcDir and MaxProcDir can be used to control the generation of process directories. ProcDir=abc will use abc instead of the 225. The user is responsible to create and remove the directories. gams.procdir% will now be defined and give you the actual process directory in use. MaxProcDir=100 will extend the usual 225a to 225z, 225aa, 225ab, etc. The defaults will be 26 for MaxProcDir and 225? for ProcDir to make everything work as before.
The GAMS parameter RunDir was removed.
The Dollar Control Options $hiddencall does the same as $call but makes sure that the statement is neither shown on the log nor the listing file. This is also true in case $ondollar or dp=2 is used. $hiddencall is especially useful in case of an encrypted model that e.g. reads/writes from an password-protected Excel file using gdxxrw password option.

GDXXRW

Support of the Excel 2007 file extension xlsm
The option password allows to pass down a password to a protect Excel file

Solvers

Baron

New libraries: version 9.0
Conopt can be used to solve nonlinear subproblems, but on 32bit platforms only (NLPSol=6)
More control over common linear subexpressions

Coin-OR

CoinScip version 1.2
- The multi-commodity-flow network cut separator is now used by default
- Improvements in heuristics, presolving, and branching
CoinGlpk version 4.39
CoinCouenne version 0.2
- A separator for disjunctive cuts has been added
CoinCplex, CoinGurobi, CoinMosek, CoinXpress
- These new bare bone solver links come free of charge with the GAMS Base system. General GAMS options (reslim, optcr, nodlim, iterlim) are supported. In addition an option file in the format required by the solver can be provided.
CoinOS 2.0
- The new experimental link to the Optimization Services project allows you to convert instances of GAMS models into the OS instance language (OSiL) format and to let an Optimization Services Server solve your instances remotely.

GUROBI

New libraries: version 2.0
Simplex performance: The simplex optimizers are much faster in the release. The improvements are most pronounced in the dual simplex method.
MIP performance: The MIP solver is significantly faster as well. Part of this is a consequence of the increased speed of the dual simplex optimizer, and part is due to algorithmic improvements in the MIP itself.
MIP IIS : You can now compute an Irreducible Inconsistent Subsystem ( IIS ) for an infeasible MIP model. The previous release could only compute IISs for continuous models.
MIP node files: You can now store search tree nodes on disk. This allows you to solve much larger and more difficult MIP models. Use the new NodefileStart parameter to indicate how much memory you would like to devote to nodes before they are written to disk. The performance impact of putting nodes out to disk is typically quite small.

MINOS

MINOS5 (old version of MINOS) was dropped. MINOS5 now is an alias to MINOS (Version 5.51) in order to protect users that hard-coded the use of MINOS5.

MOSEK

New libraries: version 6.0
Improvement of speed and stability of the interior-point optimizer for linear and conic problems
More effective presolve for simplex optimizer with hot starts

XPRESS

New libraries: version 20.00
Updated licensing: multi-threaded runs and 64-bit versions now included in base license
Updated threads option allows specification of cores left free for non-XPRESS work.

In-core communication solver links

Lindoglobal supports in-core communication

Model Libraries

GAMS Data Library

transxls (74): Solve classical transportation problem in Excel, using vba API (gamsx, opt and gdx)

GAMS EMP Library

negishi (21): Pure exchange model solved with EMP, SJM, and CGE

GAMS Model Library

bchtsp (348): Traveling Salesman Problem Instance with BCH
bchstock (349): Cutting Stock - A Column Generation Approach with BCH
tanksize (350): Tank Size Design Problem

GAMS Test Library

set10 (449): first entry in set/param data has wrong dimension
set11 (450): test for order when using set.id or set#id or #id
gdxcopy5 (451): Test GDX environment variables with trailing blanks
ifthen2 (452): Test nested $ifthen and $endif
ifthen3 (453): Test $ifthen $elseif/else $endif
ifthen4 (454): Tests $ifthen from old release notes
eval01 (455): constant evaluation with non-stop arithmetic
eval02 (456): $eval/ife/... sameas function
forceerr (457): ForceError and ForceErrorCnt Example
gdxxrw5 (458): Test for password handling of gdxxrw and $hiddencall
lolp (459): LP Test for logoption
lonlp (460): NLP Test for logoption
lomcp (461): MCP Test for logoption
eval03 (462): test constant compile time evaluation functions
eval04 (463): test constant compile time evaluation operators

Solver/Platform Availability Matrix

Solver/Platform availability - 23.3 November 1, 2009
	x86 MS Windows	x86_64 MS Windows	x86 Linux	x86_64 Linux	Sun Sparc SOLARIS	Sun Sparc64 SOLARIS	Sun Intel SOLARIS	IBM RS-6000 AIX 4.3⁴	Mac PowerPC Darwin	Mac Intel32 Darwin	Mac x86_64 Darwin	HP 9000 HP-UX 11¹	SGI IRIX²	DEC Alpha Digital Unix 4.0³
ALPHAECP
BARON 9.0		32bit		32bit				8.1
BDMLP
COIN
CONOPT 3
CPLEX 12.1								11.2				10.0	9.1	8.1
DECIS						32bit
DICOPT
GUROBI 2.0
KNITRO 6.0					5.2	32bit			5.1
LINDOGLOBAL 6.0
LGO
MILES
MINOS
MOSEK 6					5.0	5.0			5.0			3.2
MPSGE
MSNLP						32bit
NLPEC
OQNLP		32bit		32bit
OSL V3		32bit		32bit		32bit						V2	V2
OSLSE		32bit		32bit		32bit
PATH
SBB
SNOPT
XA		32bit				32bit
XPRESS 20.00								18.00				16.10
¹⁾GAMS distribution for HP 9000/HP-UX is 22.1.
²⁾GAMS distribution for SGI IRIX is 22.3.
³⁾GAMS distribution for DEC Alpha is 22.7.
⁴⁾GAMS distribution for IBM RS-6000 AIX 4.3 is 23.1.

23.3.2 Maintenance release (November 18, 2009)

Gurobi 2.0.1 library with bug fixes
MOSEK 6 rev 53 library with bug fixes
Updated CoinOS library with bug fixes
Solver optfile bug fix in GAMSCHK
Synchronized tolproj (1e-8) option for solvelink=3

23.3.3 Maintenance release (December 17, 2009)

MOSEK 6 rev 55 library with bug fixes
32bit HAR utilities available in 64bit Windows System
Slow solution reporting in GAMS/Gurobi and other solvers fixed

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