Opened 8 years ago

Closed 6 years ago

#14196 closed defect (fixed)

"subgroups" fails for C1 x C2

Reported by: mstreng Owned by: malb
Priority: major Milestone: sage-6.4
Component: group theory Keywords: abelian group subgroups invfac one
Cc: bisson Merged in:
Authors: Travis Scrimshaw Reviewers: Frédéric Chapoton
Report Upstream: N/A Work issues:
Branch: 1b92c39 (Commits) Commit: 1b92c39c04fd82fd3769abbd8059e7dda0de865b
Dependencies: Stopgaps:

Description

In Sage 5.7:

sage: A = AbelianGroup([2,1])
sage: A
Multiplicative Abelian group isomorphic to C2 x C1
sage: A.subgroups()
[Multiplicative Abelian subgroup isomorphic to C2 generated by {f0},
 Trivial Abelian subgroup]

sage: B = AbelianGroup([1,2])
sage: B
Multiplicative Abelian group isomorphic to C1 x C2
sage: B.subgroups()
Vectors not LI:  [[0, 0], [0, 1]]
...
ValueError: The given basis vectors must be linearly independent.

This last command should work just as well as A.subgroups().

Change History (13)

comment:1 Changed 8 years ago by mstreng

In Sage 5.6, it was still:

sage: A = AbelianGroup([2,1])
sage: A
Multiplicative Abelian Group isomorphic to C2
sage: A.subgroups()
[Multiplicative Abelian Group isomorphic to C2, which is the subgroup of
Multiplicative Abelian Group isomorphic to C2
generated by [f], Trivial Abelian Group, which is the subgroup of
Multiplicative Abelian Group isomorphic to C2
generated by []]
sage: B = AbelianGroup([1,2])
sage: B
Multiplicative Abelian Group isomorphic to C2
sage: B.subgroups()
[Multiplicative Abelian Group isomorphic to C2, which is the subgroup of
Multiplicative Abelian Group isomorphic to C2
generated by [f], Trivial Abelian Group, which is the subgroup of
Multiplicative Abelian Group isomorphic to C2
generated by []]

I think the situation in Sage 5.7 is an improvement, except of course for the failure to compute B.subgroups().

comment:2 Changed 8 years ago by mstreng

  • Cc bisson added

comment:3 Changed 7 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:4 Changed 7 years ago by vbraun_spam

  • Milestone changed from sage-6.1 to sage-6.2

comment:5 Changed 7 years ago by vbraun_spam

  • Milestone changed from sage-6.2 to sage-6.3

comment:6 Changed 6 years ago by vbraun_spam

  • Milestone changed from sage-6.3 to sage-6.4

comment:7 Changed 6 years ago by tscrim

  • Authors set to Travis Scrimshaw
  • Branch set to public/groups/fix_subgroups-14196
  • Commit set to 1b92c39c04fd82fd3769abbd8059e7dda0de865b
  • Component changed from commutative algebra to group theory
  • Status changed from new to needs_review

New commits:

1b92c39Fix for subgroups of abelian groups whose first part is a trivial group.

comment:8 Changed 6 years ago by ncohen

Is it me or is this commit in Sage already ?

Nathann

comment:9 Changed 6 years ago by ncohen

It seems to be me. And the trac server which seems to say that the diff between this branch and Sage is empty O_o

comment:10 Changed 6 years ago by tscrim

I think it's a trac bug that pops up sporadically.

comment:11 Changed 6 years ago by chapoton

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

ok, lgtm

comment:12 Changed 6 years ago by tscrim

Thanks Frederic.

comment:13 Changed 6 years ago by vbraun

  • Branch changed from public/groups/fix_subgroups-14196 to 1b92c39c04fd82fd3769abbd8059e7dda0de865b
  • Resolution set to fixed
  • Status changed from positive_review to closed
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