#14578: SimplicialComplex chain complex composition not zero
----------------------------------+-----------------------------------------
Reporter: vbraun | Owner: jhpalmieri
Type: defect | Status: new
Priority: major | Milestone: sage-5.10
Component: algebraic topology | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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Testcase extracted from http://ask.sagemath.org/question/2572/error-
computing-homology-of-a-simplicial-complex
{{{
sage: t0 = SimplicialComplex()
sage: t0.add_face(('a', 'b'))
sage: t0.add_face(('c', 'd', 'e'))
sage: t0.add_face(('e', 'f', 'c'))
sage: t0.homology()
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
<ipython-input-374-8061bc7260ca> in <module>()
----> 1 t0.homology()
/home/vbraun/opt/sage-5.10.beta2/local/lib/python2.7/site-
packages/sage/homology/cell_complex.pyc in homology(self, dim, **kwds)
547 # _homology_ method. See SimplicialComplex for one
example.
548 if hasattr(self, '_homology_'):
--> 549 return self._homology_(dim, **kwds)
550
551 C = self.chain_complex(cochain=cohomology, augmented=True,
/home/vbraun/opt/sage-5.10.beta2/local/lib/python2.7/site-
packages/sage/homology/simplicial_complex.pyc in _homology_(self, dim,
**kwds)
1923 kwds['subcomplex']=L
1924 C = self.chain_complex(dimensions=dims, augmented=True,
-> 1925 cochain=cohomology, **kwds)
1926 if verbose:
1927 print " Done computing the chain complex. "
/home/vbraun/opt/sage-5.10.beta2/local/lib/python2.7/site-
packages/sage/homology/simplicial_complex.pyc in chain_complex(self,
**kwds)
1786 return ChainComplex(data=differentials, degree=1,
**kwds)
1787 else:
-> 1788 return ChainComplex(data=differentials, degree=-1,
**kwds)
1789
1790 def _homology_(self, dim=None, **kwds):
/home/vbraun/opt/sage-5.10.beta2/local/lib/python2.7/site-
packages/sage/homology/chain_complex.pyc in __init__(self, data, **kwds)
460 raise TypeError, "The differentials
d_{%s} and d_{%s} are not compatible: their product is not defined." % (n,
n+degree)
461 if not prod.is_zero():
--> 462 raise ValueError, "The differentials
d_{%s} and d_{%s} are not compatible: their composition is not zero." %
(n, n+degree)
463 else:
464 if not mat.nrows() == 0:
ValueError: The differentials d_{2} and d_{1} are not compatible: their
composition is not zero.
}}}
on sage-5.10.beta2
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14578>
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