#14902: Singular NULL pointer with a ring of the form QQ(t)[x, y]/(f)
-------------------------------------+-------------------------------------
Reporter: pbruin | Owner: malb
Type: defect | Status: needs_review
Priority: major | Milestone: sage-
Component: commutative | duplicate/invalid/wontfix
algebra | Resolution:
Keywords: Singular NULL | Merged in:
pointer | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Dependencies:
Branch: |
Stopgaps: |
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Changes (by pbruin):
* status: new => needs_review
* milestone: sage-5.12 => sage-duplicate/invalid/wontfix
Old description:
> The following returns the right thing in the end, but exhibits a problem
> with calling Singular in the process:
> {{{
> sage: K.<t> = FunctionField(QQ)
> sage: A.<x,y> = PolynomialRing(K, 2)
> sage: B = A.quotient(y^2 + (t + 1)*x*y + t*y - x^3 - t*x^2)
> sage: B.gens()
> verbose 0 (3490: multi_polynomial_ideal.py, groebner_basis) Warning:
> falling back to very slow toy implementation.
> singular_ring_delete(ring*) called with NULL pointer.
> File "/home/staff/pbruin/src/sage-5.11.beta3/local/bin/sage-ipython",
> line 18, in <module>
> app.start()
> ...
> File "/home/staff/pbruin/src/sage-5.11.beta3/local/lib/python2.7/site-
> packages/sage/rings/polynomial/multi_polynomial_ideal.py", line 910, in
> _groebner_strategy
> return GroebnerStrategy(MPolynomialIdeal(self.ring(),
> self.groebner_basis()))
> Exception KeyError: (The ring pointer 0x0,) in
> 'sage.libs.singular.ring.singular_ring_delete' ignored
> (xbar, ybar)
> }}}
> Probably Gröbner bases shouldn't even be invoked in this example, but
> that is another question.
New description:
(Duplicate of #12188)
The following returns the right thing in the end, but exhibits a problem
with calling Singular in the process:
{{{
sage: K.<t> = FunctionField(QQ)
sage: A.<x,y> = PolynomialRing(K, 2)
sage: B = A.quotient(y^2 + (t + 1)*x*y + t*y - x^3 - t*x^2)
sage: B.gens()
verbose 0 (3490: multi_polynomial_ideal.py, groebner_basis) Warning:
falling back to very slow toy implementation.
singular_ring_delete(ring*) called with NULL pointer.
File "/home/staff/pbruin/src/sage-5.11.beta3/local/bin/sage-ipython",
line 18, in <module>
app.start()
...
File "/home/staff/pbruin/src/sage-5.11.beta3/local/lib/python2.7/site-
packages/sage/rings/polynomial/multi_polynomial_ideal.py", line 910, in
_groebner_strategy
return GroebnerStrategy(MPolynomialIdeal(self.ring(),
self.groebner_basis()))
Exception KeyError: (The ring pointer 0x0,) in
'sage.libs.singular.ring.singular_ring_delete' ignored
(xbar, ybar)
}}}
Probably Gröbner bases shouldn't even be invoked in this example, but that
is another question.
--
Comment:
I posted a patch for #12188 that fixes this ticket as well. Now the
output of the above example is
{{{
verbose 0 (3490: multi_polynomial_ideal.py, groebner_basis) Warning:
falling back to very slow toy implementation.
(xbar, ybar)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/14902#comment:3>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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