#11403: NTL error while inverting q-adic number with fixed modulus precision
---------------------------------------------+------------------------------
Reporter: jdemeyer | Owner: was
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.4
Component: padics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Jeroen Demeyer, David Roe | Merged in:
Dependencies: | Stopgaps:
---------------------------------------------+------------------------------
Changes (by saraedum):
* status: needs_work => needs_review
Old description:
> {{{
> sage: R.<t> = Zq(8,2,'fixed-mod')
> sage: 1/(t+t^2)
> ...
> Unhandled SIGABRT: An abort() occurred in Sage.
> }}}
>
> Note that {{{t + t^2}}} is invertible:
> {{{
> sage: R.<t> = Zq(8,2,'fixed-mod')
> sage: u = (t+1) + 2*t^2; u
> (t + 1) + t^2*2 + O(2^2)
> sage: u * (t + t^2)
> 1 + O(2^2)
> }}}
>
> Part of the issue is a missing {{{sig_on()}}}/{{{sig_off()}}}.
> After applying [attachment:11403_sig.patch], the error becomes more
> descriptive:
> {{{
> sage: R.<t> = Zq(8,2,'fixed-mod')
> sage: 1/(t+t^2)
> ---------------------------------------------------------------------------
> RuntimeError Traceback (most recent call
> last)
>
> /usr/local/src/sage-4.7/devel/sage-main/<ipython console> in <module>()
>
> /usr/local/src/sage-4.7/local/lib/python2.6/site-
> packages/sage/structure/element.so in
> sage.structure.element.RingElement.__div__
> (sage/structure/element.c:12757)()
>
> /usr/local/src/sage-4.7/local/lib/python2.6/site-
> packages/sage/structure/coerce.so in
> sage.structure.coerce.CoercionModel_cache_maps.bin_op
> (sage/structure/coerce.c:6436)()
>
> /usr/local/src/sage-4.7/local/lib/python2.6/site-
> packages/sage/structure/element.so in
> sage.structure.element.RingElement.__div__
> (sage/structure/element.c:12731)()
>
> /usr/local/src/sage-4.7/local/lib/python2.6/site-
> packages/sage/rings/padics/padic_ZZ_pX_FM_element.so in
> sage.rings.padics.padic_ZZ_pX_FM_element.pAdicZZpXFMElement._div_
> (sage/rings/padics/padic_ZZ_pX_FM_element.cpp:6781)()
>
> RuntimeError: ZZ_p: division by non-invertible element
> }}}
>
> -----
>
> Apply
>
> 1. [[attachment:11403_sig.patch]]
> 1. [[attachment:11403_fix.patch]]
>
> to the sage repository.
New description:
{{{
sage: R.<t> = Zq(8,2,'fixed-mod')
sage: 1/(t+t^2)
...
Unhandled SIGABRT: An abort() occurred in Sage.
}}}
Note that {{{t + t^2}}} is invertible:
{{{
sage: R.<t> = Zq(8,2,'fixed-mod')
sage: u = (t+1) + 2*t^2; u
(t + 1) + t^2*2 + O(2^2)
sage: u * (t + t^2)
1 + O(2^2)
}}}
Part of the issue is a missing {{{sig_on()}}}/{{{sig_off()}}}.
After applying [attachment:11403_sig.patch], the error becomes more
descriptive:
{{{
sage: R.<t> = Zq(8,2,'fixed-mod')
sage: 1/(t+t^2)
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call
last)
/usr/local/src/sage-4.7/devel/sage-main/<ipython console> in <module>()
/usr/local/src/sage-4.7/local/lib/python2.6/site-
packages/sage/structure/element.so in
sage.structure.element.RingElement.__div__
(sage/structure/element.c:12757)()
/usr/local/src/sage-4.7/local/lib/python2.6/site-
packages/sage/structure/coerce.so in
sage.structure.coerce.CoercionModel_cache_maps.bin_op
(sage/structure/coerce.c:6436)()
/usr/local/src/sage-4.7/local/lib/python2.6/site-
packages/sage/structure/element.so in
sage.structure.element.RingElement.__div__
(sage/structure/element.c:12731)()
/usr/local/src/sage-4.7/local/lib/python2.6/site-
packages/sage/rings/padics/padic_ZZ_pX_FM_element.so in
sage.rings.padics.padic_ZZ_pX_FM_element.pAdicZZpXFMElement._div_
(sage/rings/padics/padic_ZZ_pX_FM_element.cpp:6781)()
RuntimeError: ZZ_p: division by non-invertible element
}}}
-----
Apply
1. [[attachment:trac_11403.patch]]
to the sage repository.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11403#comment:11>
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