Opened 7 months ago

Closed 6 months ago

#21760 closed defect (fixed)

Fix tensor products for some chain complexes

Reported by: jhpalmieri Owned by:
Priority: major Milestone: sage-7.5
Component: algebraic topology Keywords:
Cc: tscrim Merged in:
Authors: Travis Scrimshaw Reviewers: Frédéric Chapoton
Report Upstream: N/A Work issues:
Branch: 3b86bf3 (Commits) Commit: 3b86bf3c19f38097304933da9e08420ddfb8c732
Dependencies: Stopgaps:

Description

When tensoring chain complexes, tensor products of two 0 x n matrices don't work correctly:

sage: C = ChainComplex({0: matrix(ZZ, 0, 1)}, degree=-1)
sage: ascii_art(C)
 0 <-- C_0 <-- 0 
sage: C.homology()
{0: Z}

sage: C.tensor(C)
Trivial chain complex over Integer Ring
sage: C.tensor(C).homology()
{}

Change History (4)

comment:1 Changed 6 months ago by tscrim

  • Authors set to Travis Scrimshaw
  • Branch set to public/homology/fix_tensor_product_chain_complexes-21760
  • Commit set to 3b86bf3c19f38097304933da9e08420ddfb8c732
  • Status changed from new to needs_review

So, I should not try to optimize if it is a 0 x n differential matrix; those still carry useful information.


New commits:

3b86bf3Premature optimization is the root of not handling 0 x n matrices.

comment:2 Changed 6 months ago by chapoton

  • Reviewers set to Frédéric Chapoton
  • Status changed from needs_review to positive_review

ok, let it be

comment:3 Changed 6 months ago by jhpalmieri

Thank you for the fix and the review.

comment:4 Changed 6 months ago by vbraun

  • Branch changed from public/homology/fix_tensor_product_chain_complexes-21760 to 3b86bf3c19f38097304933da9e08420ddfb8c732
  • Resolution set to fixed
  • Status changed from positive_review to closed
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