#12770: cartesian product of directed graphs
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Reporter: chapoton | Owner: jason, ncohen, rlm
Type: defect | Status: positive_review
Priority: major | Milestone: sage-5.0
Component: graph theory | Resolution:
Keywords: directed graph, product | Work issues:
Report Upstream: N/A | Reviewers: Frédéric Chapoton
Authors: David Coudert | Merged in:
Dependencies: | Stopgaps:
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Comment (by dcoudert):
Replying to [comment:14 nthiery]:
> Replying to [comment:11 dcoudert]:
> > Unfortunately your proposal is slower than the implementation of this
patch.
>
> Interesting that calling repeatedly add_edge is faster than add_edges!
The point is that using add_edges, we first create a new list of edges,
and then iterate this list to add edges to the new graph. So somehow we do
the job twice. My tests suggest that current implementation is a bit
faster.
> I am fine with the current implementation, though maybe using
edge_iterator would be faster, since the former does a sort (which I don't
like but that's another story). I let you see if you want to do that.
I have changed the patch to use the edge_iterator. It is now slightly
faster (few ms less on large graphs).
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12770#comment:15>
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