cdd does not correctly handle floating point precision issues. It works for 
non-degenerate input, for everything else there are no guarantees. 



On Wednesday, July 1, 2015 at 12:27:09 PM UTC+2, Dima Pasechnik wrote:
>
> While working on http://trac.sagemath.org/ticket/10276, we had trouble 
> running Polyhedron with RDF precision.
> An explicit example showing the issue is in  
> http://trac.sagemath.org/raw-attachment/ticket/10276/x.sage
>
> What happens is that Polyhedron() finishes normally, but it creates 
> something that looks like inconsistent data
> (a closer inspection reveals that one of the 136 facets of this polytope 
> does not "contain any vertices", in the
> sense that the corresponding inequality is not satisfied with equality 
> (within the meaningful precision)).
> At least this data is not good enough to compute the face lattice of it.
>
> Without a better knowledge of Polyhedron() code it is hard for me to 
> decide whether this is a bug.
>
> Any comments?
> Thanks,
> Dima
>
> PS. if I use non-default 'field' backend I also get some weird error on 
> this data, but it works fine if I use
> QQ as the base_ring.
>
>

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