Opened 11 years ago

Closed 9 years ago

#11231 closed defect (worksforme)

Sparse and dense polynomials hash differently, but are equal.

Reported by: robertwb Owned by: jason
Priority: major Milestone: sage-duplicate/invalid/wontfix
Component: misc Keywords:
Cc: Merged in:
Authors: Reviewers: Christian Nassau
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Status badges

Description 

sage: R = PolynomialRing(ZZ, 'x', sparse=False)
sage: S = PolynomialRing(ZZ, 'x', sparse=True)
sage: R
Univariate Polynomial Ring in x over Integer Ring
sage: S
Sparse Univariate Polynomial Ring in x over Integer Ring
sage: R == S
True
sage: hash(R) == hash(S)
False

It's unclear what equality really means here...

Change History (3)

comment:1 Changed 9 years ago by tscrim

  • Milestone set to sage-duplicate/invalid/wontfix
  • Status changed from new to needs_review

In 5.5.rc0, I get the following: 

sage: R = PolynomialRing(ZZ, 'x', sparse=False)
sage: S = PolynomialRing(ZZ, 'x', sparse=True)
sage: R
Univariate Polynomial Ring in x over Integer Ring
sage: S
Sparse Univariate Polynomial Ring in x over Integer Ring
sage: R == S
False
sage: hash(R) == hash(S) # on a 32-bit VM
True

However this isn't a problem.

comment:2 Changed 9 years ago by cnassau

  • Reviewers set to cnassau
  • Status changed from needs_review to positive_review

I've checked that, indeed, already Sage 5.4.1 gives this answer (different objects, same hash). And I would love to give a ticket a positive review (my first), so here we go...

comment:3 Changed 9 years ago by jdemeyer

  • Resolution set to worksforme
  • Reviewers changed from cnassau to Christian Nassau
  • Status changed from positive_review to closed
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