Hi,
Does anybody know how to convert the Gams file to *.mpi or *.mps? I have already studied the given information in this webpage: https://www.gams.com/latest/docs/solver ... index.html, but I found the information very confusing. I would be appreciate if anybody could provide me with some clear information about converting Gams files.
Thanks in advance,
Masood
Convert Gams files to *.mpi or *.mps Topic is solved
Re: Convert Gams files to *.mpi or *.mps
Hi Masood,
The example below is based on the well known transportation problem from the GAMS model library (https://www.gams.com/latest/gamslib_ml/ ... sport.html) and illustrates how to create an MPS file using Convert.
I hope this helps!
Fred
The example below is based on the well known transportation problem from the GAMS model library (https://www.gams.com/latest/gamslib_ml/ ... sport.html) and illustrates how to create an MPS file using Convert.
Code: Select all
Sets
i canning plants / seattle, sandiego /
j markets / newyork, chicago, topeka / ;
Parameters
a(i) capacity of plant i in cases
/ seattle 350
sandiego 600 /
b(j) demand at market j in cases
/ newyork 325
chicago 300
topeka 275 / ;
Table d(i,j) distance in thousands of miles
newyork chicago topeka
seattle 2.5 1.7 1.8
sandiego 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/ ;
*** Modifications
* choose convert as solver
option lp = convert;
* write convert option file
$echo fixedMPS transport.mps > convert.opt
* instruct convert to look for a solver option file
transport.optfile = 1;
Solve transport using lp minimizing z ;
Fred
Re: Convert Gams files to *.mpi or *.mps
Hi Ferd,
I am really appreciate your help. I was looking for this piece of code for a couple of weeks. You made my day!!
Thanks again,
Masood
I am really appreciate your help. I was looking for this piece of code for a couple of weeks. You made my day!!
Thanks again,
Masood

 User
 Posts: 85
 Joined: 2 years ago
Re: Convert Gams files to *.mpi or *.mps
you can also choose solver CPlex to write mps or LP file, which will contain the exact variable names in it, good for problem debugging. or you can choose to turn off the names in mps file as well using the option 'names no' in cplex option.
Code: Select all
Sets
i canning plants / seattle, sandiego /
j markets / newyork, chicago, topeka / ;
Parameters
a(i) capacity of plant i in cases
/ seattle 350
sandiego 600 /
b(j) demand at market j in cases
/ newyork 325
chicago 300
topeka 275 / ;
Table d(i,j) distance in thousands of miles
newyork chicago topeka
seattle 2.5 1.7 1.8
sandiego 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/ ;
*** Modifications
* choose cplex as solver
option lp = cplex;
* write convert option file
$echo writeMPS transport.mps > cplex.o98
* instruct convert to look for a solver option file
transport.optfile = 98;
Solve transport using lp minimizing z ;
Masood wrote:Hi Ferd,
I am really appreciate your help. I was looking for this piece of code for a couple of weeks. You made my day!!
Thanks again,
Masood
Re: Convert Gams files to *.mpi or *.mps
Thank you yanzhiping!
Would you please let me know more about "cplex.o98" and "transport.optfile = 98"? Why we need to have "98" and "o98" instead of "1" and "opt"?
Would you please let me know more about "cplex.o98" and "transport.optfile = 98"? Why we need to have "98" and "o98" instead of "1" and "opt"?