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).
If you eliminate all but very few variables (e.g. 0 or 1 left) it you
can also use linear programming.
Sure, as a first approximation this can be useful but in the end I will
probably want a polyhedron in a few dimensions.
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