#20935: Weird crash in arithmetic mod prime powers
---------------------------------+--------------------------------
Reporter: davidloeffler | Type: defect
Status: new | Priority: major
Milestone: sage-7.3 | Component: basic arithmetic
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
---------------------------------+--------------------------------
The following code crashes in Sage v7.2 with a !ZeroDivisionError:
{{{
V = FreeModule(Zmod(3^10), 1)
v = V.gen(0)
x = v * v
x.valuation(3)
}}}
The variable x is just 1 (mod 3^10^), and if you just do {{{
Zmod(3^10)(1).valuation(3)}}} it returns 0 (as it should), but creating it
via linear algebra in this way seems to somehow return a broken object.
Oddly enough, only powers of 3 between 3^10^ and 3^19^ (inclusive) seem to
raise this error -- larger or smaller powers work fine. Similarly powers
of 2 between 2^16^ and 2^30^, or powers of 5 between 5^7^ and 5^13^. This
strongly suggests there is an overflow error occurring somewhere when the
modulus is too large for a 16-bit integer but large enough for a 32-bit.
--
Ticket URL: <https://trac.sagemath.org/ticket/20935>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
