#9063: wrong type for denominator
-----------------------------------------+----------------------------------
Reporter: cjh | Owner: AlexGhitza
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.5.3
Component: algebra | Keywords:
Author: Luis Felipe Tabera Alonso | Upstream: N/A
Reviewer: John Cremona | Merged:
Work_issues: |
-----------------------------------------+----------------------------------
Changes (by cremona):
* status: needs_review => needs_work
* reviewer: => John Cremona
Comment:
This looks good to me. It applied ok to 4.5.3.alpha1, and all (long)
tests pass, except for one:
{{{
sage -t -long "sage/matrix/matrix2.pyx"
**********************************************************************
File "/storage/jec/sage-4.5.3.alpha1/devel/sage-
tests/sage/matrix/matrix2.pyx", line 4665:
sage: M.weak_popov_form()
Exception raised:
Traceback (most recent call last):
File "/home/jec/sage-current/local/bin/ncadoctest.py", line 1231, in
run_one_test
self.run_one_example(test, example, filename, compileflags)
File "/home/jec/sage-current/local/bin/sagedoctest.py", line 38, in
run_one_example
OrigDocTestRunner.run_one_example(self, test, example, filename,
compileflags)
File "/home/jec/sage-current/local/bin/ncadoctest.py", line 1172, in
run_one_example
compileflags, 1) in test.globs
File "<doctest __main__.example_68[7]>", line 1, in <module>
M.weak_popov_form()###line 4665:
sage: M.weak_popov_form()
File "matrix2.pyx", line 4748, in
sage.matrix.matrix2.Matrix.weak_popov_form (sage/matrix/matrix2.c:26417)
::
File "/home/jec/sage-current/local/lib/python/site-
packages/sage/matrix/matrix_misc.py", line 90, in weak_popov_form
den = R(lcm([a.denominator() for a in M.list()]))
File "/home/jec/sage-current/local/lib/python/site-
packages/sage/rings/arith.py", line 1527, in lcm
return __LCM_sequence(seq)
File "/home/jec/sage-current/local/lib/python/site-
packages/sage/rings/arith.py", line 1583, in __LCM_sequence
g = vi.lcm(g)
File "element.pyx", line 306, in
sage.structure.element.Element.__getattr__ (sage/structure/element.c:2632)
return getattr_from_other_class(self,
self.parent().category().element_class, name)
File "parent.pyx", line 268, in
sage.structure.parent.getattr_from_other_class
(sage/structure/parent.c:2835)
raise_attribute_error(self, name)
File "parent.pyx", line 170, in
sage.structure.parent.raise_attribute_error (sage/structure/parent.c:2602)
raise AttributeError, "'%s.%s' object has no attribute
'%s'"%(cls.__module__, cls.__name__, name)
AttributeError: 'sage.rings.finite_rings.integer_mod.IntegerMod_int'
object has no attribute 'lcm'
**********************************************************************
1 items had failures:
}}}
The problem is in the function weak_popov_form() in
sage/rings/matrix/matrix_misc.py (which was only merged into Sage
receontly -- and I was, by chance, its reviewer). There one has matrices
of polynomials over fields and the code tries to clear denominators, by
forming the LCM of the denominators; and that now fails when those
denominators are all equal to 1 in a finite field!
Rather than mess with the weakpopov form code, this could be solved if
there was an lcm function for finite field elements which always returned
1 (except lcm(0,0)=0, perhaps).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9063#comment:4>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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