#16681: Random doctest failures in sage/rings/algebraic_closure_finite_field.py
---------------------------------+------------------------
Reporter: vbraun | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: number theory | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
---------------------------------+------------------------
Changes (by vbraun):
* cc: pbruin, defeo, vdelecroix, mmarco (added)
Old description:
> This is caused by #15390.
>
> First of all, you should use a form of assert that gives some minimal
> information when it can fail, e.g. in the form below.
>
> The following fails occasionally on OSX 10.9 (cf.
> algebraic_closure_finite_field.py line 910)
> {{{
> sage: K = GF(3).algebraic_closure()
> sage: R = PolynomialRing(K, 'T')
> sage: T = R.gen()
> sage: for d in xrange(1000):
> ....: p = R.random_element(degree=8)
> ....: assert p.factor().prod() == p, p.factor()
> ....:
> ---------------------------------------------------------------------------
> AssertionError Traceback (most recent call
> last)
> <ipython-input-22-f31a401fb53b> in <module>()
> 1 for d in xrange(Integer(1000)):
> 2 p = R.random_element(degree=Integer(8))
> ----> 3 assert p.factor().prod() == p, p.factor()
> 4
>
> AssertionError: T * (T + 1) * (T + z5 + 1) * (T + z5^3 + 1) * (T + 2*z5^4
> + z5) * (T + 2*z5^4 + 2*z5^2) * (T + 2*z5^4 + 2*z5^3 + z5^2 + z5)
> }}}
>
> On a related note, a random element can be zero:
> {{{
> sage: K = GF(3).algebraic_closure()
> sage: R = PolynomialRing(K, 'T')
> sage: T = R.gen()
> sage: for d in xrange(1000):
> ....: p = R.random_element(degree=randint(2,8))
> ....: assert p.factor().prod() == p, p
> ....:
> ---------------------------------------------------------------------------
> ValueError Traceback (most recent call
> last)
> <ipython-input-15-db4aacba08d5> in <module>()
> 1 for d in xrange(Integer(1000)):
> 2 p =
> R.random_element(degree=randint(Integer(2),Integer(8)))
> ----> 3 assert p.factor().prod() == p, p
> 4
>
> /home/release/Sage/local/lib/python2.7/site-
> packages/sage/rings/polynomial/polynomial_element.so in
> sage.rings.polynomial.polynomial_element.Polynomial.factor
> (build/cythonized/sage/rings/polynomial/polynomial_element.c:23530)()
>
> ValueError: factorization of 0 not defined
> }}}
New description:
This is caused by #15390
{{{
sage -t --long src/sage/rings/algebraic_closure_finite_field.py
**********************************************************************
File "src/sage/rings/algebraic_closure_finite_field.py", line 940, in
sage.rings.algebraic_closure_finite_field.AlgebraicClosureFiniteField_generic._factor_univariate_polynomial
Failed example:
for d in xrange(10):
p = R.random_element(degree=randint(2,8))
assert p.factor().prod() == p
Exception raised:
Traceback (most recent call last):
File "/Users/buildslave-
sage/slave/sage_git/build/local/lib/python2.7/site-
packages/sage/doctest/forker.py", line 480, in _run
self.execute(example, compiled, test.globs)
File "/Users/buildslave-
sage/slave/sage_git/build/local/lib/python2.7/site-
packages/sage/doctest/forker.py", line 839, in execute
exec compiled in globs
File "<doctest
sage.rings.algebraic_closure_finite_field.AlgebraicClosureFiniteField_generic._factor_univariate_polynomial[4]>",
line 3, in <module>
assert p.factor().prod() == p
AssertionError
**********************************************************************
1 item had failures:
1 of 6 in
sage.rings.algebraic_closure_finite_field.AlgebraicClosureFiniteField_generic._factor_univariate_polynomial
}}}
First of all, you should use a form of assert that gives some minimal
information when it can fail, e.g. in the form below. The following fails
occasionally and makes it easy enough to reproduce:
{{{
sage: K = GF(3).algebraic_closure()
sage: R = PolynomialRing(K, 'T')
sage: T = R.gen()
sage: for d in xrange(1000):
....: p = R.random_element(degree=8)
....: assert p.factor().prod() == p, p.factor()
....:
---------------------------------------------------------------------------
AssertionError Traceback (most recent call
last)
<ipython-input-22-f31a401fb53b> in <module>()
1 for d in xrange(Integer(1000)):
2 p = R.random_element(degree=Integer(8))
----> 3 assert p.factor().prod() == p, p.factor()
4
AssertionError: T * (T + 1) * (T + z5 + 1) * (T + z5^3 + 1) * (T + 2*z5^4
+ z5) * (T + 2*z5^4 + 2*z5^2) * (T + 2*z5^4 + 2*z5^3 + z5^2 + z5)
}}}
On a related note, a random element can be zero:
{{{
sage: K = GF(3).algebraic_closure()
sage: R = PolynomialRing(K, 'T')
sage: T = R.gen()
sage: for d in xrange(1000):
....: p = R.random_element(degree=randint(2,8))
....: assert p.factor().prod() == p, p
....:
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
<ipython-input-15-db4aacba08d5> in <module>()
1 for d in xrange(Integer(1000)):
2 p =
R.random_element(degree=randint(Integer(2),Integer(8)))
----> 3 assert p.factor().prod() == p, p
4
/home/release/Sage/local/lib/python2.7/site-
packages/sage/rings/polynomial/polynomial_element.so in
sage.rings.polynomial.polynomial_element.Polynomial.factor
(build/cythonized/sage/rings/polynomial/polynomial_element.c:23530)()
ValueError: factorization of 0 not defined
}}}
--
--
Ticket URL: <http://trac.sagemath.org/ticket/16681#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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