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hypersimplex for special cases

Posted: 30 Aug 2012, 09:28
by xammy
Is there a specific reason why hypersimplex(0,d) and hypersimplex(d,d) are not allowed? Of course the resulting polytopes are just single points but I really "needed" them:

For example, one can describe the even-parity polytope (convex hull of 0/1 points with even number of 1's) by a disjunctive-programming construction (convex hull of union of polyhedra) of all k-hypersimplices for which k is an even integer. Using my extension for extended formulations this works as follows for the odd case:

Code: Select all

($Q,$Proj) = construct_disjunctive_program(hypersimplex(1,6), hypersimplex(3,6), hypersimplex(5,6));
(here $Q is the extended formulation and you obtain the odd-parity polytope if you apply the projection via matrix $Proj)

Since I want to be able to do the same thing for the even case, I need hypersimplex(0,6), etc...

Best regards,

Matthias

Re: hypersimplex for special cases

Posted: 30 Aug 2012, 12:15
by joswig
Your complaint is totally justified. I just changed the code accordingly. Please check [10918].

Re: hypersimplex for special cases

Posted: 13 Sep 2012, 14:12
by xammy
Perfect! I'm happy now :)