#9782: Enhanced fans fail for complicated cases
----------------------------------+-----------------------------------------
Reporter: vbraun | Owner: novoselt
Type: defect | Status: new
Priority: major | Milestone: sage-4.5.3
Component: algebraic geometry | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Fans of toric varieties do not work correctly, for example see the
following:
{{{
sage: f = Fan([(0, 2, 4), (0, 4, 5), (0, 3, 5), (0, 1, 3), (0, 1, 2), (2,
4, 6), (4, 5, 6), (3, 5, 6), (1, 3, 6), (1, 2, 6)], [(-1, 0, 0), (0, -1,
0), (0, 0, -1), (0, 0, 1), (0, 1, 2), (0, 1, 3), (1, 0, 4)])
sage: f.is_complete()
True
sage: X = ToricVariety(f)
sage: X.fan().is_complete()
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/home/vbraun/opt/sage-4.5.2/devel/sage-main/<ipython console> in
<module>()
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/fan.pyc in is_complete(self)
1742 # Then boundary cones are (d-1)-dimensional.
1743 for cone in self(codim=1):
-> 1744 if len(cone.star_generator_indices()) != 2:
1745 self._is_complete = False
1746 return False
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/fan.pyc in __call__(self, dim, codim)
816 else:
817 return self.cones(dim, codim)
--> 818
819 def __cmp__(self, right):
820 r"""
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/fan.pyc in cones(self, dim, codim)
1547 if len(top_cones) == self.ngenerating_cones():
1548 top_cones.sort(key=lambda cone:
-> 1549
cone.star_generator_indices()[0])
1550 levels[-1] = top_cones
1551 if len(levels) >= 2: # We have rays
/home/vbraun/Sage/sage/local/lib/python2.6/site-
packages/sage/geometry/fan.pyc in <lambda>(cone)
1548 top_cones.sort(key=lambda cone:
1549
cone.star_generator_indices()[0])
-> 1550 levels[-1] = top_cones
1551 if len(levels) >= 2: # We have rays
1552 rays = list(levels[1])
IndexError: tuple index out of range
}}}
I'm pretty sure it is a bug in Andrey's switch to enhanced cones for toric
varieties (`trac_9470_toric_variety_fans.patch`). If I back out that patch
it works fine. Unfortunately we didn't catch that in our doctests, we
should add tests for complicated toric varieties and mark them as `# long
time`
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9782>
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