#9880: Segfault in PyNaC 0.2.0.p4
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Reporter: jpflori | Owner: burcin
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.6.2
Component: symbolics | Keywords: pynac
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by jpflori):
Replying to [comment:21 vbraun]:
> I don't understand the GiNaC documentation that you referred to
(http://www.ginac.de/reference/structGiNaC_1_1expair__rest__is__less.html).
They state it is not a SWO, and their example is that neither 3*x<2*x nor
2*x<3*x. But thats perfectly fine in a SWO, you can have incomparable
elements. The only constraint on incomparable elements is transitivity,
that is, if A and B are incomparable and B and C are incomparable then A
and C are also incomparable. Do you understand why its not a SWO?
I have no idea why GiNaC order is not an SWO, my point was just to link
that page where the GiNaC devs state it is not one.
However I never had problems with it so far, so maybe it is a SWO and the
statement in GiNaC doc is just wrong.
We should post on GiNaC mailing list to get more info on that one. Maybe
Burcin knows also.
What is definitely sure is that the modified order used in pynac is not
correct. Because of it the result of a call to std::sort is flawed. This
can be not too harmful (e.g. automatic simplification does not occur
because terms which should be adjacent in the internal structure are not)
but can also lead to segfaults (even if that dramatic side effect seems to
depend on something mysterious, potentially on the gcc version used as you
stated).
So at least for me, using the original GiNaC order solves many problems.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9880#comment:23>
Sage <http://www.sagemath.org>
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