#16964: MPolynomialIdeal_singular_repr.variety: sage.libs.pari.gen.PariError:
not
enough precomputed primes
----------------------------+----------------------------------------------
Reporter: gagern | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.4
Component: algebraic | Keywords: variety qqbar cmp singular
geometry | Authors:
Merged in: | Report Upstream: N/A
Reviewers: | Branch:
Work issues: | Dependencies:
Commit: |
Stopgaps: |
----------------------------+----------------------------------------------
I just spent 8 hours in an attempt to solve a polynomial system of
equations using ideal.variety(). After these 8 hours I was left with the
following error message:
{{{
File "sage/rings/polynomial/multi_polynomial_ideal.py", line 604, in
__call__
return self.f(self._instance, *args, **kwds)
File "sage/rings/polynomial/multi_polynomial_ideal.py", line 2671, in
variety
V.sort()
File "sage/rings/qqbar.py", line 3889, in __cmp__
rcmp = cmp(self.real(), other.real())
File "sage/rings/qqbar.py", line 4529, in __cmp__
return self._sub_(other).sign()
File "sage/rings/qqbar.py", line 4864, in sign
return self.sign()
File "sage/rings/qqbar.py", line 4867, in sign
self.exactify()
File "sage/rings/qqbar.py", line 3600, in exactify
self._set_descr(self._descr.exactify())
File "sage/rings/qqbar.py", line 7849, in exactify
left.exactify()
File "sage/rings/qqbar.py", line 3600, in exactify
self._set_descr(self._descr.exactify())
File "sage/rings/qqbar.py", line 7594, in exactify
rv.exactify()
File "sage/rings/qqbar.py", line 3600, in exactify
self._set_descr(self._descr.exactify())
File "sage/rings/qqbar.py", line 7849, in exactify
left.exactify()
File "sage/rings/qqbar.py", line 3600, in exactify
self._set_descr(self._descr.exactify())
File "sage/rings/qqbar.py", line 7851, in exactify
gen = left._exact_field().union(right._exact_field())
File "sage/rings/qqbar.py", line 2362, in union
newpol, self_pol, k = pari_nf.rnfequation(my_factor, 1)
File "gen.pyx", line 7454, in sage.libs.pari.gen.gen.rnfequation
(build/cythonized/sage/libs/pari/gen.c:37964)
File "handle_error.pyx", line 90, in
sage.libs.pari.handle_error._pari_handle_exception
(build/cythonized/sage/libs/pari/handle_error.c:1181)
sage.libs.pari.gen.PariError: not enough precomputed primes
}}}
This is extremely annoying, since apparently the result of the computation
was available at that point, and it was only sorting the result which
failed. Neither the unsorted result nor the triangular decomposition had
been cached, throwing away 8 hours worth of computation. So I suggest
1. wrap that sorting into a try-except block to return the result unsorted
if there is any problem sorting things.
2. perhaps provide a switch to disable sorting up front, since repeated
exactification might cost time.
3. Try to work out why exactly the comparison fails here, and avoid this
error in the first place.
The system of equations in this exact form was written by someone else, so
I'll have to either reproduce this with my own (equivalent) system or
request permission to post that code. In any case, it's rather lengthy.
I'll also try to run the code on a modified sage which simply disables the
sort in order to get my hands on the bare QQbar descriptions behind the
failed computation.
--
Ticket URL: <http://trac.sagemath.org/ticket/16964>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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