#7540: Speed up shortest_path_all_pairs() and update distance_graph
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Reporter: ncohen | Owner: rlm
Type: enhancement | Status: new
Priority: major | Milestone: sage-4.3
Component: graph theory | Keywords:
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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As mentionned in #7533 by Rob Beezer, the function
shortest_path_all_pairs() is much slower than computing independently all
the distances, which is a bit worrying. Easy explanation ( at least it is
an explanation for me, though there may be a deeper one ), distance() is a
function from NetworkX while the Floyd-Marshall algorithm is directly
written in Python, hence the slowness.
This function is very fundamental and should be improved ! The difference
is amazing :
{{{
sage: g=graphs.RandomGNP(200,.1)
sage: time e=g.shortest_path_all_pairs()
CPU times: user 16.51 s, sys: 0.06 s, total: 16.57 s
Wall time: 16.60 s
sage: time a=[g.distance(i,j) for (i,j) in Subsets(g,2)]
CPU times: user 1.06 s, sys: 0.00 s, total: 1.06 s
Wall time: 1.06 s
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7540>
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