On Mon, Jul 11, 2022 at 8:24 PM 'Peter Mueller' via sage-support
<sage-support@googlegroups.com> wrote:
>
> OK, calling "sage -sh" and setting "export qe="~/local/sage/local" allows to
> start qepcad without relocating files. However, qepcad fails for this rather
> small example , telling "Failure occurred in: GCSI (final check) Reason
> for the failure: Too few cells reclaimed." So either (i) qepcad has a bug
> here, or (ii) qepcad's abilities are rather limited, or (iii) I'm not using
> it the right way. If (i) or (ii) applies, there is little hope for
> improvements, since the project seems to have abandoned in 2012.
qepcad is certainly too old to be saved. One ought to implement
cylindrical algebraic decomposition (CAD)
in a modern way, e.g. in Sage...
On a practical side of things, I'd have converted your system into a
system of equations (using squares etc
to model inequalities) and then looked for real solutions only (e.g.
using msolve).
HTH
Dima
>
> dim...@gmail.com schrieb am Montag, 11. Juli 2022 um 19:11:08 UTC+2:
>>
>>
>>
>> On Mon, 11 Jul 2022, 17:04 'Peter Mueller' via sage-support,
>> <sage-s...@googlegroups.com> wrote:
>>>
>>> Thanks for the suggestion, I wasn't aware of this feature. However, here it
>>> results in "Error HELPFRD: Could not open
>>> ~/local/sage/local/bin/qepcad/share/qepcad/qepcad.help". Unfortunately, the
>>> binary of qepcad is the file ~/local/sage/local/bin/qepcad, so I cannot
>>> symlink the existing help page (at
>>> ~/local/sage/local/share/qepcad/qepcad.help) to the place where qepcad is
>>> looking for it.
>>
>>
>> you can move ~/local/sage/local/bin/qepcad
>> somewhere (e.g. rename it) and create the necessary link.
>>
>>>
>>>
>>>
>>> dim...@gmail.com schrieb am Montag, 11. Juli 2022 um 17:40:11 UTC+2:
>>>>
>>>>
>>>>
>>>> On Mon, 11 Jul 2022, 16:33 'Peter Mueller' via sage-support,
>>>> <sage-s...@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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