Opened 6 years ago

Closed 6 years ago

#14902 closed defect (duplicate)

Singular NULL pointer with a ring of the form QQ(t)[x, y]/(f)

Reported by: pbruin Owned by: malb
Priority: major Milestone: sage-duplicate/invalid/wontfix
Component: commutative algebra Keywords: Singular NULL pointer
Cc: Merged in:
Authors: Reviewers: Jeroen Demeyer, Peter Bruin, Volker Braun
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description (last modified by pbruin)

(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.

Change History (6)

comment:1 Changed 6 years ago by jdemeyer

Looks very much like #12188.

comment:2 Changed 6 years ago by kcrisman

Volker says that this ask.sagemath question is a duplicate as well.

comment:3 Changed 6 years ago by pbruin

  • Description modified (diff)
  • Milestone changed from sage-5.12 to sage-duplicate/invalid/wontfix
  • Status changed from new to needs_review

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)

comment:4 Changed 6 years ago by vbraun

  • Authors set to Peter Bruin
  • Reviewers set to Volker Braun
  • Status changed from needs_review to positive_review

I agree, same issue as #12188.

comment:5 Changed 6 years ago by jdemeyer

  • Authors Peter Bruin deleted
  • Reviewers changed from Volker Braun to Jeroen Demeyer, Peter Bruin, Volker Braun

comment:6 Changed 6 years ago by jdemeyer

  • Resolution set to duplicate
  • Status changed from positive_review to closed
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