On 2014-05-16, Jeroen Demeyer <[email protected]> wrote: > On 2014-05-15 11:33, Volker Braun wrote: >> On Thursday, May 15, 2014 8:45:47 AM UTC+1, Jeroen Demeyer wrote: >> >> > IMHO, Jeroen needs to use Fourier-Motzkin elimination. >> Yes, something like that. Elimination based purely on the H-rep without >> first computing the V-rep. Is this implemented in Sage? In PPL? >> >> >> So is that the question, you have a problem where you can not compute >> the V-representation of the initial set of inequalities? > Essentially yes, although it is also a matter of patience... > The projected polyhedron is much simpler than the original polyhedron > before projecting. > >> There is no special support for doing the Fourier-Motzkin elimination of >> variables in Sage, but then its a pretty straightforward reshuffling of >> the inequalities. Then one can hope to apply double description in lower >> dimension. > Of course, but I personally don't feel like implementing this (I also > don't really know about the algorithms behind this).
Perhaps Volker's http://trac.sagemath.org/ticket/16101 can be used as a good starting point. I didn't read the code, but how else does he go between V and H-representations, if not by Fourier-Motzkin... Dima -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
