GAMS — The Solver Manuals - Available Software

408 MPSWRITE
the macros @i and @j. In the string, ANALYZE recognizes the characters between ’&’ and ’:’ as representing
the stem of the index name corresponding to the string following the ’@’ macro in the gams file, and the number
immediately following the ’:’ as the number of characters from the left of the row/column name that the particular
set label stem begins. As an illustration, in the row syntax for X, we see the strings &I.:2 and &J.:4. This means
that in any row of X, say XSENE, the label corresponding to I begins at the second position (SE) while the label
corresponding to J begins at the fourth position (NE). This is used by the ANALYZE command EXPLAIN. For
further information on this topic, consult the ANALYZE manual.
The ANALYZE LP file shown in the ”ANALYZE LP file with FIXED=1” demonstrates the effect of the option
fixed which uses a fixed field format for the LP file. This makes the file size larger but at the same time it is
easier to read.
Modified ’trnsport.gms’
\$TITLE A TRANSPORTATION PROBLEM (TRNSPORT,SEQ=1)
\$OFFUPPER
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 from @i to @j
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)) ;