#18839: Boost Dominator Tree
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Reporter: borassi | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.8
Component: graph theory | Resolution:
Keywords: Dominator tree, | Merged in:
Boost | Reviewers:
Authors: Michele Borassi | Work issues:
Report Upstream: N/A | Commit:
Branch: | 81e4ee11c8db417b6f5b5ec478da01bdcfd19ab7
u/borassi/boost_dominator_tree | Stopgaps:
Dependencies: #18811, #18564 |
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Comment (by borassi):
> However, I have questions on the expected behavior:
> - with 1-vertex graph:
> {{{
> sage: G = graphs.[wiki:PathGraph](1)
> sage: G.dominator_tree(0)
> {0: None}
> sage: G.dominator_tree(0, return_dict=False)
> Graph on 0 vertices
> }}}
You are right, if the dominator tree is empty (that is, if from the root
we cannot reach any other vertex) it is better to output a 1-vertex graph
containing the root, not an empty graph. For the dictionary, I think the
behavior is correct.
> - With disconnected graphs
> {{{
> sage: G = 2 * graphs.[wiki:PathGraph](1)
> sage: G.dominator_tree(0)
> {0: None, 1: None}
> sage: G = 2 * graphs.[wiki:PathGraph](2)
> sage: G.dominator_tree(0)
> {0: None, 1: 0, 2: None, 3: None}
> }}}
> If this is effectively what we expect, then I will finalize the review.
Here, the behavior is correct, in my opinion. I have changed the doc to
better explain this case, by adding an "OUTPUT" block.
--
Ticket URL: <http://trac.sagemath.org/ticket/18839#comment:13>
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