#8148: looking at the dual of a poset: IndexError
-----------------------------+----------------------------------------------
Reporter: jhpalmieri | Owner: sage-combinat
Type: defect | Status: new
Priority: major | Milestone: sage-4.8
Component: combinatorics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
-----------------------------+----------------------------------------------
Comment(by brunellus):
{{{
sage:Poset({1: [], 3: [], 2: [1, 3]}).dual().relations()
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call
last)
/root/<ipython console> in <module>()
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/combinat/posets/posets.pyc in relations(self)
717 - Rob Beezer (2011-05-04)
718 """
--> 719 return list(self.relations_iterator())
720
721 def relations_iterator(self):
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/combinat/posets/posets.pyc in relations_iterator(self)
745 # Relies on vertices the fact that _elements correspond to
the rows and
746 # columns of the lequal matrix
--> 747 leq_mat = self.lequal_matrix()
748 n = leq_mat.nrows()
749 elements = self._elements
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/combinat/posets/posets.pyc in lequal_matrix(self, **kwds)
1282 False
1283 """
-> 1284 return self._hasse_diagram.lequal_matrix(**kwds)
1285
1286 def meet_matrix(self):
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/combinat/posets/hasse_diagram.pyc in lequal_matrix(self,
ring, sparse)
867 D = {}
868 for i in range(n):
--> 869 for v in self.breadth_first_search(i):
870 D[(i,v)] = 1
871 self._leq_matrix = matrix(ring, n, n, D, sparse=sparse)
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/graphs/generic_graph.pyc in breadth_first_search(self,
start, ignore_direction, distance, neighbors)
11565 # Preferably use the Cython implementation
11566 if neighbors is None and not isinstance(start,list) and
distance is None and hasattr(self._backend,"breadth_first_search"):
> 11567 for v in self._backend.breadth_first_search(start,
ignore_direction = ignore_direction):
11568 yield v
11569 else:
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/graphs/base/c_graph.so in
sage.graphs.base.c_graph.Search_iterator.__next__
(sage/graphs/base/c_graph.c:19732)()
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/graphs/base/sparse_graph.so in
sage.graphs.base.sparse_graph.SparseGraph.out_neighbors
(sage/graphs/base/sparse_graph.c:8007)()
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/graphs/base/sparse_graph.so in
sage.graphs.base.sparse_graph.SparseGraph.out_neighbors
(sage/graphs/base/sparse_graph.c:7841)()
/root/Sage/sage/local/lib/python2.6/site-
packages/sage/graphs/base/c_graph.so in
sage.graphs.base.c_graph.CGraph.check_vertex
(sage/graphs/base/c_graph.c:5697)()
RuntimeError: Vertex (0) is not a vertex of the graph.
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8148#comment:2>
Sage <http://www.sagemath.org>
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