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by mbrandt
09 Jun 2020, 19:42
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

Hi, I did as you suggested. Here are the error messages: polytope > print matroidal(edge_directions($PC->GRAPH, $p->VERTICES)); polymake: WARNING: Compiling temporary shared module, please be patient... {"app": "polytope", "embed": "edge_directions.cc", "inst": [ {"args": ["void", "perl::Canned<cons...
by mbrandt
07 Jun 2020, 01:47
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

Hi, I have just updated my version of Polymake, and the above code no longer works. I get the following error (after running the line print matroidal(edge_directions($PC->GRAPH, $p->VERTICES));): polymake: ERROR: C++/perl Interface module compilation failed; most likely due to a type mismatch. Set t...
by mbrandt
29 Sep 2017, 19:39
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

Ah, sorry. In my own code I had been using simplicial complexes when a polyhedral complex was needed. Sorry for the confusion.
by mbrandt
28 Sep 2017, 23:27
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

Thank you so much for your help! I will just make one remark that if the subdivision is not a triangulation then one instead needs to use a polyhedral complex. Otherwise, extra edges will be added when Polymake makes a simplicial complex and these will likely not be of the form e_i-e_j. An example (...
by mbrandt
28 Sep 2017, 19:18
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

One last question: If I wanted to check whether a regular subdivision was matroidal or not, how would I do this? Is there a property like EDGE_DIRECTIONS which I could apply to the subdivision (or the simplicial complex coming from the subdivision)?
by mbrandt
27 Sep 2017, 19:52
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Re: Checking if a polytope is a matroid polytope

Thanks for the reply. I have never written any subroutines in perl and am not very familiar with the language. I wrote the following attempt at a solution: sub matroidal { my @M = shift(@_); my $bool = 1; foreach @vector (@M) { if (scalar(grep {$_ =~ 1} @vector) ==1) { if (scalar(grep {$_ =~ -1} @ve...
by mbrandt
25 Sep 2017, 21:26
Forum: General Discussion
Topic: Checking if a polytope is a matroid polytope
Replies: 12
Views: 6379

Checking if a polytope is a matroid polytope

A theorem by [GGMS] says that a polytope with vertices in \{0,1\}^n is a matroid polytope if and only if every edge of the polytope is parallel to e_i - e_j for some i and j . My question is, has this been implemented somewhere in polymake? Specifically, I would like to be able to ask if a polytope ...

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