I am running Sage 3.1.4 under Fedora 9 and have found a bug in the
file graph.py.
-------------------------------------------------------------------
sage: G = DiGraph({0:{}, 1:{0:1}, 2:{0:1}}, weighted = True)
sage: G.weighted_adjacency_matrix()
[0]
[1]
[1]
sage: G.adjacency_matrix()
[0 0 0]
[1 0 0]
[1 0 0]
sage: G.laplacian_matrix()
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/home/davidp/.sage/temp/xyzzy/16886/
_home_davidp_math_sandpile_sage_sandpile_sage_14.py in <module>()
----> 1
2
3
4
5
/usr/local/sage-3.1.4-fc8-i686-Linux/local/lib/python2.5/site-packages/
sage/graphs/graph.pyc in kirchhoff_matrix(self, weighted,
boundary_first)
904 S = [sum(M.row(i)) for i in range(M.nrows())]
905 for i in range(len(A)):
--> 906 A[i][i] = S[i]
907 return M.parent()(A)
908
/usr/local/sage-3.1.4-fc8-i686-Linux/local/lib/python2.5/site-packages/
sage/modules/free_module_element.so in
sage.modules.free_module_element.FreeModuleElement_generic_sparse.__setitem__
(sage/modules/free_module_element.c:15074)()
1765
1766
-> 1767
1768
1769
IndexError: index (i=1) must be between 0 and 0
sage:
------------------------------------------------------------------------------------
The laplacian_matrix function is not working because
weighted_adjacency matrix is not returning a square matrix. A
suggested fix is to change line 845 (in the graph.py code for
weighted_adjacency_matrix) from
M = matrix(D, sparse=sparse)
to
M = matrix(self.num_verts(), D, sparse=sparse)
David
P.S. This is my first time posting to sage-devel. Would it be
appropriate for me to fix this bug myself and somehow send the code to
Sage? If so, is there a document explaining how to do this?
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