#10731: IndexError in toric sheaf cohomology
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Reporter: vbraun | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone: sage-4.6.2
Component: algebraic geometry | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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This computation dies unnecessarily:
{{{
sage: cell24 = Polyhedron(vertices=[
... (1,0,0,0),(0,1,0,0),(0,0,1,0),(0,0,0,1),(1,-1,-1,1),(0,0,-1,1),
... (0,-1,0,1),(-1,0,0,1),(1,0,0,-1),(0,1,0,-1),(0,0,1,-1),(-1,1,1,-1),
... (1,-1,-1,0),(0,0,-1,0),(0,-1,0,0),(-1,0,0,0),(1,-1,0,0),(1,0,-1,0),
...
(0,1,1,-1),(-1,1,1,0),(-1,1,0,0),(-1,0,1,0),(0,-1,-1,1),(0,0,0,-1)])
sage: X = ToricVariety(FaceFan(cell24.lattice_polytope()))
sage: D = -X.divisor(0)
sage: D.cohomology()
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/home/vbraun/Sage/24cell/<ipython console> in <module>()
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/schemes/generic/toric_divisor.pyc in _sheaf_cohomology(self,
cplx)
1544 assert(h[1].dimension()==0)
1545 continue
-> 1546 HH_list[ h[0]+1 ] = h[1].dimension()
1547
1548 return vector(ZZ, HH_list)
IndexError: list assignment index out of range
}}}
Inside, the homology of an auxiliary simplicial complex is computed. For
sufficiently complicated cases, vector spaces of dimension 0 are sometimes
returned even if all higher-dimensional homology groups vanish. My sheaf
cohomology code wrongly assumed that this would not be the case.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10731>
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