Monday, July 28, 2008

GDX question

> I would like to make a gdx dump of all the sets/paramters/scalars of
> my model, but I do not want any equations or variables in there at
> all.


$version 227

Sets
i canning plants / seattle, san-diego /
j markets / new-york, chicago, topeka / ;

Parameters

a(i) capacity of plant i in cases
/ seattle 350
san-diego 600 /

b(j) demand at market j in cases
/ new-york 325
chicago 300
topeka 275 / ;

Table d(i,j) distance in thousands of miles
new-york chicago topeka
seattle 2.5 1.7 1.8
san-diego 2.5 1.8 1.4 ;

Scalar f freight in dollars per case per thousand miles /90/ ;

Parameter c(i,j) transport cost in thousands of dollars per case ;

c(i,j) = f * d(i,j) / 1000 ;

Variables
x(i,j) shipment quantities in cases
z total transportation costs in thousands of dollars ;

Positive Variable x ;

Equations
cost define objective function
supply(i) observe supply limit at plant i
demand(j) satisfy demand at market j ;

cost .. z =e= sum((i,j), c(i,j)*x(i,j)) ;

supply(i) .. sum(j, x(i,j)) =l= a(i) ;

demand(j) .. sum(i, x(i,j)) =g= b(j) ;

Model transport /all/ ;

Solve transport using lp minimizing z ;

Display x.l, x.m ;


* generate include file execute_unload statement
* that write all symbols except variables and
* equations
$onecho > f.awk
BEGIN {
print "execute_unload 'mygdx'" > "temp1.inc"
}
/^ *[0-9]+ / {
if ($4=="Equ") next;
if ($4=="Var") next;
print "," $2 > "temp1.inc"
}
END {
print ";" > "temp1.inc"
}
$offecho
$gdxout temp1
$unload
$gdxout
$call 'gdxdump temp1 symbols > temp1.txt'
$call 'awk -f f.awk temp1.txt'
$include temp1.inc

* mygdx.gdx will not contain any variables or equations
execute 'gdxdump mygdx symbols';


Basically at compile time we dump a gdx file temp1.gdx that has all symbols. Then we use an AWK scripts (still at GAMS compile time) to generate an include file temp1.inc that contains an execute_unload statement with all non var/equ symbols to mygdx.gdx. Then we $include this file. Finally for checking we call gdxdump (at execution time) to show all symbols in mygdx.gdx.