On Mon, 11 Jul 2022, 16:33 'Peter Mueller' via sage-support, <
sage-support@googlegroups.com> wrote:
> When running
>
> var('p1', 'p2', 'p3', 'q1', 'q2', 'q3')
> qf = qepcad_formula
> # q1 = p1
> l = [p1+q1 == 1, 0 < p1, p1 < 1,
> 0 <= p2, p2 <= 1, 0 <= q2, q2 <= 1,
> p2 + p1*q1 + q2 == 1,
> 0 <= p3, p3 <= 1, 0 <= q3, q3 <= 1,
> p3 + p2*q1 + p1*q2 + q3 == 1]
> F = qepcad_formula.and_(l)
> qepcad(F, solution='any-point')
>
> I get the wrong answer
>
> ValueError: input formula is false everywhere
>
> However, this set of inequalities has solutions. In fact, if there were no
> solution, this should hold even more if we remove the comment in
>
> # q1 = p1
>
> above. However, doing that produces a correct solution
>
> {'p1': 1/2, 'p2': 0, 'p3': 0, 'q2': 3/4, 'q3': 5/8}.
>
> Am I doing something wrong? If it is a bug, then I don't know if comes
> from the interface to qepcad, or qepcad itself.
>
you can try running qepcad standalone, at
./sage -sh
prompt, and try reproducing...
https://www.usna.edu/CS/qepcadweb/B/QEPCAD.html
>
> I've tried the above example in Sage versions 9.6 and 9.7.beta3 on a linux
> machine.
>
> -- Peter Mueller
>
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