#12607: ChainComplex reports zero homology groups (depending on ChomP)
----------------------------------+-----------------------------------------
Reporter: vbraun | Owner: jhpalmieri
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: algebraic topology | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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As reported on https://groups.google.com/d/msg/sage-release/gW9IsTBrVII
/eGL-ih824vAJ, whether or not ChomP is installed changes the output of
`ChainComplex.homology` by trivial pieces:
{{{
sage -t -long -force_lib "devel/sage-main/sage/geometry/fan.py"
**********************************************************************
File "/64bitdev/storage/sage/sage-5.0.beta6/devel/sage-main/sage/
geometry/fan.py", line 2779:
sage: fan.complex().homology()
Expected:
{0: 0, 1: 0, 2: Z x Z, 3: 0}
Got:
{2: Z x Z, 3: 0}
**********************************************************************
File "/64bitdev/storage/sage/sage-5.0.beta6/devel/sage-main/sage/
geometry/fan.py", line 2783:
sage: fan.complex().homology()
Expected:
{0: 0, 1: 0, 2: Z, 3: 0}
Got:
{2: Z, 3: 0}
}}}
The fact that zero-dimensional cohomology groups are reported above and
below the non-trivial range is already somewhat annoying, so I propose to
fix this by changing the `homology` method to chop off these irrelevant
zeroes. This would then have the additional benefit of the representation
no longer depending on whether or not ChomP is installed. So the output
for the homology of the 2-sphere should be
{{{
{0: Z, 1: 0, 2: Z}
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12607>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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