#6660: Error in chromatic_number() and coloring() in the Graph class
--------------------------+-------------------------------------------------
Reporter: ncohen | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-4.1.1
Component: graph theory | Keywords:
Reviewer: | Author:
Merged: |
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Description changed by ncohen:
Old description:
> (see : http://groups.google.com/group/sage-
> devel/browse_thread/thread/2707c2ef0362b8b0 )
>
> The following code creates a Graph and computes its chromatic number :
>
> sage: h=Graph(":I`ASWCaG`WaJC{afP")
>
> sage: h.chromatic_number()
>
> 4
>
> sage: h.coloring()
>
> [[6, 8], [9], [0, 4, 7, 3], [1, 2, 5]]
>
> Meanwhile, you can check that the coloring [[3, 9, 1], [9, 4, 0, 3], [3,
> 8, 5]] is valid with this code that checks that each class is actually an
> independent set.
> :
>
> for c in [[3, 9, 1], [9, 4, 0, 3], [3, 8, 5]]:
>
> print h.subgraph(c).connected_components_number()==len(c)
New description:
(see : http://groups.google.com/group/sage-
devel/browse_thread/thread/2707c2ef0362b8b0 )
The following code creates a Graph and computes its chromatic number :
sage: h=Graph(":I`ASWCaG`WaJC{afP")
sage: h.chromatic_number()
4
sage: h.coloring()
[[6, 8], [9], [0, 4, 7, 3], [1, 2, 5]]
Meanwhile, you can check that the coloring [[3, 9, 1], [9, 4, 0, 3], [3,
8, 5]] is valid with this code that checks that each class is actually an
independent set.
:
for c in [[3, 9, 1], [9, 4, 0, 3], [3, 8, 5]]:
print h.subgraph(c).connected_components_number()==len(c)
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6660#comment:2>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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