GAMS advanced syntax From McCarl Guide From own guess-based experiments

System Attributes

Gams Attributes

System Attributes System.<attribute>  Parameter report1(*); Set report2(*);  report1("memory")=%system.memory%;  report2("%system.date%")=yes;  display report1,report2;

GAMS Attributes Command line arguments gams.<attribute>  Parameter report1(*); Set report2(*);  report1(“lpsolver")=%gams.lp%;  report2("%gams.lp%")=yes;  display report1,report2;

GAMS Timing Compilation Syntax check $control operations Execution Syntax execution

At Execution Time Execute normal GAMS syntax:  Data(Set)=normal(10,2);  Solve, If, Sum, Smin, Loop, …  Execute, Execute_unload  Option, Display, …

At Compilation Time  Check GAMS syntax  Execute special $ sign syntax  $call  $load  $unload

Save Restart  Break code into sequentially executed pieces  Avoids compile time problems (if code segment 1 produces a file to be used in code segment 2)  Can be nicely automated

$ Dollar Options  $ must be in first column  Several $ options can be in one line  $onlisting offsymlist  Some options require values, e.g.   Generally, carried out at compile time!

External file inclusion $include filename $libinclude filename $libinclude filename $batinlcude filename $batinlcude filename $sysinclude filename $sysinclude filename Can append path statements before filename (absolute, relative, %var%)

GDX $Control Variables $Gdxin filename.gdx $Load p1 s1 $Gdxin $Gdxout filename.gdx $Unload p1 s1  dangerous because $Gdxout of compile time For unload use better: Execute_Unload

Output (*.lst file) $Control  $onlisting  $offlisting  $onuellist  $offuellist  $onupper  $offupper  $show  $single  $double  $onsymlist  $offsymlist  $onsymxref  $offsymxref  $offdollar  $ondollar  $offinclude  $oninclude  …

Input file control  $offmargin  $onmargin  $mincol 20 maxcol 40  $ondelim  $offdelim  $ontext  $offtext  $offglobal  $onglobal

Messages / Comments  $log  $error  $error  $remark  $title  $stitle  $hidden  $oneolcom  $offeolcom  $oninline  $offinline  $offnestcom  $onnestcom

GAMS syntax symbol substitution  $comment  $comment  $stars  $dollar  $eolcom  $inlinecom Why change?

Forced program termination $exit… quits only local file $abort text… stops entire compilation $stop… stops without error $goto name… jumps to: $label name Usually these termination statements are combined with $if statements

Control Variables  $set name value  $setlocal name value  $setglobal name value  $drop name  $droplocal name  $dropglobal name Action scope differs: (setlocal < set < setglobal) (setlocal < set < setglobal)

Conditional Control Statements  $If condition statementtoexecute  $Ifi… case insensitive $if version  $ife…  $ifthen  $ifelse  $else

GAMS Symbol Tests $if exist filename statement $if dexist dirname statement $if declared symbol statement $if dimension 4 symbol statement $if defined symbol statement $if putopen statement $if settype symbol statement (partype, filtype, equtype, vartype, modtype, …) $if errorfree gamsstatement $if errorlevel n gamsstatement $if warnings gamsstatement Statement can be special or normal gams syntax

File Creation at Compile Time  $Onecho > file  $Offecho

$Macro  $macro ratio(a,b) a/b  $macro reciprocal(a) 1/a  Scalar a /2/,d/4/,c;  c=ratio(a,d); display c;  c=reciprocal(d);

Other features  ask  Allows user dialog

Undocumented $maxgoto$onuni