Search found 39 matches

Go to advanced search

by opfer
19 Apr 2018, 07:39
Forum: General Discussion
Topic: facets of a mixed ILP
Replies: 7
Views: 26008

Re: facets of a mixed ILP

Well, I have to admit that I don't know whether there is an algorithm for calculating mixed-integer polytopes in polymake. We will have to ask my colleagues. In the tutorial that you mentioned, the continuous variables are projected out. Do you want to keep them or do you want to project them out? B...
by opfer
18 Apr 2018, 20:57
Forum: General Discussion
Topic: facets of a mixed ILP
Replies: 7
Views: 26008

Re: facets of a mixed ILP

Hi, thanks for the LP file. Could you please elaborate a little on which information you need. Solving the LP and iterating the integer solutions seems rather easy. There are only 4 different feasible assignments for the integer variables. Are you looking for facets that belong to the convex hull of...
by opfer
18 Apr 2018, 16:30
Forum: General Discussion
Topic: facets of a mixed ILP
Replies: 7
Views: 26008

Re: facets of a mixed ILP

Please post the LP file. I don't know whether it helps, but it might be interesting to have a look at it.

Best regards,
Thomas
by opfer
31 Mar 2018, 18:59
Forum: Helpdesk
Topic: Calling functions in Mathematica from Polymake.
Replies: 2
Views: 5057

Re: Calling functions in Mathematica from Polymake.

I guess the biggest problem is that you are on Windows. While it might be possible to use the callable library to somehow connect Mathematica and polymake, I doubt, you will get polymake up and running natively on Windows. Maybe the easiest way is to transfer data between Mathematica and polymake th...
by opfer
02 Mar 2018, 21:43
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

it makes a minor difference in my codes whether something is an equality or an inequality, so I somehow lost some theoretical understanding. Hmm, at least you should deal with them differently when importing them as input, shouldn't you? Yes and no. The interface to polymake (which was not written ...
by opfer
02 Mar 2018, 17:16
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

Thanks for elaborating. When implementing my solver code, these things were all just "constraints", as it makes a minor difference in my codes whether something is an equality or an inequality, so I somehow lost some theoretical understanding.

Best regards,
Thomas
by opfer
02 Mar 2018, 09:38
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

Well, there are not that many ways to define a facet, I guess. The only source of confusion I could imagine might be the concrete matrix representation: if you have a linear system A*x <= B, you have to specify INEQUALITIES and FACETS as a block matrix (B | -A) because polymake's polyhedra are alwa...
by opfer
01 Mar 2018, 23:14
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

There is absolutely no magic. You create a Polytope object with INEQUALITIES and EQUATIONS, then add an LP subobject with LINEAR_OBJECTIVE vector and ask for LP.MINIMAL_VALUE or LP.MAXIMAL_VALUE or LP.MINIMAL_VERTEX or LP.MAXIMAL_VERTEX. Depending on your current preferences, either your implementa...
by opfer
27 Feb 2018, 20:22
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

Hi, if I add the output of "Affine hull:" (189 constraints) instead of "Facets:" (32 constraints) to the IP and make in an LP, then I obtain 178 as optimal value. (Adding the factes yields 163.429 .) I hope my colleagues can explain this. I am not an expert on how Polymake handle...
by opfer
27 Feb 2018, 08:26
Forum: Helpdesk
Topic: Discrepancy in computing facets of a mixed integer program
Replies: 29
Views: 22957

Re: Discrepancy in computing facets of a mixed integer program

Hi!

Could you try to zip the file and attach it afterwards? If this still does not work, could you upload it somewhere?

Best regards,
Thomas

Go to advanced search