simplicial complexes: add_face doesn't clear enough cached data

[jhpalmieri]

Running add_face on a simplicial complex doesn't clear various data related to homology calculations:

sage: T = SimplicialComplex([range(1,5)]).n_skeleton(1)
sage: T.homology()
{0: 0, 1: Z x Z x Z}
sage: T.add_face([1,2,3])
sage: T.homology() # should be free of rank 2
{0: 0, 1: Z x Z x Z, 2: 0}
sage: SimplicialComplex(T.facets()).homology()
{0: 0, 1: Z x Z, 2: 0}

See also http://ask.sagemath.org/question/2391/homology-of-simplicial-complexes.

CC: @tscrim

Component: algebraic topology

Author: John Palmieri

Reviewer: Travis Scrimshaw

Merged: sage-5.9.beta2

Issue created by migration from https://trac.sagemath.org/ticket/14354

[tscrim]

comment:4

Could you make self.__contractible = {} to self.__contractible = None to be consistent with the initial state (I also think this will result in a speedup for larger complexes since I think it will know to compute a large contractible subcomplex)? Other than that, I think this looks good. Thanks.

[jhpalmieri]

comment:5

Good point, thanks. Fixed now.

[jhpalmieri]

Attachment: trac_14354-simplicial.patch.gz

[tscrim]

comment:6

Thank you.

[tscrim]

Reviewer: Travis Scrimshaw

[jdemeyer]

Merged: sage-5.9.beta2