#10874: Add support for keep_labels in
Digraph.strongly_connected_components_digraph
---------------------------------+------------------------------------------
Reporter: nthiery | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.7
Component: graph theory | Keywords: strongly connected components
Author: Nicolas M. Thiéry | Upstream: N/A
Reviewer: Nathann Cohen | Merged:
Work_issues: |
---------------------------------+------------------------------------------
Old description:
> With keep_labels=True, the method
> Digraph.strongly_connected_components_digraph keeps the label on edges
> when contracting strongly connected components, and returns a multi-
> digraph::
> {{{
> sage: g = DiGraph({0:{1:"0-12", 2: "0-12", 3: "0-3"}, 1: {2:
> "1-2", 3: "1-3"}, 2:{1: "2-1", 3: "2-3"}})
> sage: scc_digraph =
> g.strongly_connected_components_digraph(keep_labels = True)
> sage: scc_digraph.edges()
> [({0}, {3}, "0-3"), ({0}, {1, 2}, '0-12'),
> ({1, 2}, {3}, '1-3'), ({1, 2}, {3}, '2-3'),
> ({1, 2}, {1, 2}, '1-2'), ({1, 2}, {1, 2}, '2-1')]
> }}}
New description:
With keep_labels=True, the method
Digraph.strongly_connected_components_digraph keeps the label on edges
when contracting strongly connected components, and returns a multi-
digraph::
{{{
sage: g = DiGraph({0:{1:"0-12", 2: "0-12", 3: "0-3"}, 1: {2:
"1-2", 3: "1-3"}, 2:{1: "2-1", 3: "2-3"}})
sage: scc_digraph =
g.strongly_connected_components_digraph(keep_labels = True)
sage: scc_digraph.edges()
[({0}, {3}, "0-3"), ({0}, {1, 2}, '0-12'),
({1, 2}, {3}, '1-3'), ({1, 2}, {3}, '2-3'),
({1, 2}, {1, 2}, '1-2'), ({1, 2}, {1, 2}, '2-1')]
}}}
APPLY:
* trac_10874-graph-strongly_connected_componnents-nt.patch
* trac_10874-reviewer.patch
--
Comment(by ncohen):
What about avoiding to test "keep_labels" twice ? `:-)`
Here is a reviewer patch which does just that. Your patch is good to go,
so you can set this ticket to "positive review" if you agree with my
modifications, and also if you don't for some reason (please update the
"apply" section in this case) `:-)`
Nathann
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10874#comment:2>
Sage <http://www.sagemath.org>
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