#7184: Implement counting of spanning trees for graphs and digraphs
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Reporter: AJonsson | Owner: rlm
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.2
Component: graph theory | Keywords:
Work_issues: | Author:
Reviewer: | Merged:
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Comment(by ncohen):
Sorryyyyyyy !! I had forgotten to edit your function after I edited
kirchhoff_matrix !
Here is a new patch removing this line which is now integrated into
kirchhoff_matrix. Besides, I wanted to do something about
{{{
for i in self.vertices():
M[j,j]=self.in_degree(i)
if (self.vertices()[j]== root_vertex):
M[j,j]= M[j,j] + 1
j= j + 1
}}}
With these lines, you are evaluating all the vertices at each look, just
to return its jth element. As the vertices do not change, you could have
stored the list of vertices in a variable, each time trying to find the
jth element of this list ( without listing allt he vertices again ). But
with this new patch, you are just getting the index of the vertex you are
interested in, and updating the matrix... And with some luck, this patch
is the last one :-)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7184#comment:14>
Sage <http://www.sagemath.org>
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