#13294: Add test for not necessarly induced subgraphs to Graph.is_subgraph()
method
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Reporter: steven | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_review
Priority: minor | Milestone: sage-5.2
Component: graph theory | Resolution:
Keywords: graph, induced subgraph | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Description changed by steven:
Old description:
> That attached patch allows for testing if a graph is a subgraph of
> another,
> either induced or not.
> The current implementation only tests for
> induced subgraphs.
>
> A boolean parameter named "induced" has been added to
> Graph.is_subgrapg().
> That parameter defaults to True for backward compatibility.
>
> {{{
> def is_subgraph(self, other, induced=True):
> }}}
>
> If induced is True the method behaves like the current one, testing if
> 'self' is an *induced* subgraph of other.
>
> If induces is False the method tests if all vertices and all edges of
> self are also in other.
>
> This example illustrates the difference:
> {{{
> sage: H=graphs.CycleGraph(5)
> sage: G=graphs.PathGraph(5)
> sage: G.is_subgraph(H)
> False
> sage: G.is_subgraph(H, induced=False)
> True
> }}}
>
> The patch also includes a couple of fixes regarding docstrings.
>
> As a personal note, I think that since the method is named "is_subgraph"
> and not "is_induced_subgraph" the default behaviour is counter-intuitive.
New description:
That attached patch allows for testing if a graph is a subgraph of
another,
either induced or not.
The current implementation only tests for
induced subgraphs.
A boolean parameter named "induced" has been added to Graph.is_subgraph().
That parameter defaults to True for backward compatibility.
{{{
def is_subgraph(self, other, induced=True):
}}}
If induced is True the method behaves like the current one, testing if
'self' is an *induced* subgraph of other.
If induces is False the method tests if all vertices and all edges of self
are also in other.
This example illustrates the difference:
{{{
sage: H=graphs.CycleGraph(5)
sage: G=graphs.PathGraph(5)
sage: G.is_subgraph(H)
False
sage: G.is_subgraph(H, induced=False)
True
}}}
The patch also includes a couple of fixes regarding docstrings.
As a personal note, I think that since the method is named "is_subgraph"
and not "is_induced_subgraph" the default behaviour is counter-intuitive.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13294#comment:2>
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