CODEWITHSUNDEEP
glpkscipmathprog
Kitserve
Kitserve

Reputation: 117

Is it possible to convert a MathProg MIP file to a format recognised by SCIP?

I've been using GLPK to solve some mixed integer programming problems. Here's a sample input file in MathProg format:

set REACTIONS;
set REACTANTS;
param Ys {i in REACTANTS, j in REACTIONS};
param Gamma {i in REACTANTS, j in REACTIONS};
param eps;
param delt;
var w {i in REACTANTS} >=-delt <=delt;
var R0 {i in REACTIONS} >=0 <=1, integer;
var Rn {i in REACTIONS} >=0 <=1, integer;
minimize z:  sum{i in REACTIONS} -Rn[i];
s.t. const1{i in REACTIONS} : sum{k in REACTANTS} w[k]*Gamma[k,i] <= delt*(1-R0[i]);
s.t. const2{i in REACTIONS} : -sum{k in REACTANTS} w[k]*Gamma[k,i] <= delt*(1-R0[i]);
s.t. const3{i in REACTIONS} : Rn[i] <= 1-R0[i];
s.t. const5{i in REACTIONS} : sum{k in REACTANTS} w[k]*Gamma[k,i] <= delt*(1-Rn[i])-eps;
s.t. const6{i in REACTIONS, j in REACTIONS: i <> j} : sum{k in REACTANTS} w[k]*(Ys[k,i]-Ys[k,j]) <= delt*(1-Rn[i]+Rn[j]+R0[j]);
data;
set REACTIONS:= 1 2 3 4 5 6;
set REACTANTS:= 1 2 3 4 5 6;
param Ys:   1   2   3   4   5   6:=
1    1  0   0   0   0   0
2    1  0   0   0   0   0
3    0  1   1   0   0   0
4    0  0   0   1   0   0
5    0  0   0   1   0   0
6    0  0   0   0   1   1;
param Gamma:    1   2   3   4   5   6:=
1    -1 1   0   0   0   1
2    -1 1   1   0   0   0
3    1  -1  -1  0   0   0
4    0  0   1   -1  1   0
5    0  0   0   -1  1   1
6    0  0   0   1   -1  -1;
param eps:=0.1;
param delt:=10;
end;

I've been running into performance problems for bigger problems of this type, and since SCIP claims to be several times faster than GLPK for MIP, it seems worth investigating. However, I haven't been able to make head or tail of the documentation when it comes to input file formats. SCIP's homepage says that it supports AMPL format, and the GLPK's homepagesays that MathProg is a subset of AMPL. Trying to feed the above file into SCIP 3.1.0 via scip -f file.nl returns the following error:

read problem <file.nl>
============

no reader for input file <file.nl> available

I'm not sure whether this is because I've failed to build SCIP with AMPL support, or something else. I found this blog post on building SCIP with AMPL support, but the instructions seem to be outdated as the source zip of SCIP 3.1.0 doesn't contain an interfaces folder.

So, I have two questions:

  1. Is it possible to get SCIP to recognise my MathProg input as is?
  2. If not, can anyone advise on how to convert it to a recognised format? An automated method would be preferable, as I don't really want to have to learn yet another format, but a manual method would be better than nothing.

Thanks for any help and apologies for my ignorance!

Upvotes: 3

Views: 1114

Answers (1)

Gregor
Gregor

Reputation: 1375

As I indicated in my comment above, the Ampl-interface is still included in the SCIP-distribution, and you should be able to compile it and read your problem as documented in the excellent blog post you cite.

If you feel tempted to try different file formats, I see two options for you:

  1. use glpk for translating your problem into a file format that is recognizable by SCIP. I found methods glp_write_mps() and glp_write_lp. SCIP can read both .lp and .mps-files. Make sure that you use exactly these file extensions, because SCIP doesn't recognize files in .lp-format but ending with .txt instead.
  2. Use Zimpl to formulate your problems instead. The two formats of Zimpl and Ampl are strikingly similar, see the documentation for examples and further reference. Problem descriptions in Zimpl can be translated into .lp-format or read directly by SCIP, if you compile SCIP with the ZIMPL=true-option, which is the default.

Upvotes: 3

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