#12389: Bug in graph coloring
----------------------------+-----------------------------------------------
Reporter: ncohen | Owner: jason, ncohen, rlm
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: graph theory | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author: Nathann Cohen
Merged: | Dependencies:
----------------------------+-----------------------------------------------
Geoff Tims reported the following bug :
{{{
sage: sub = graphs.PetersenGraph()
sage: sub.complement().chromatic_number(algorithm="MILP")
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/home/ncohen/<ipython console> in <module>()
/home/ncohen/.Sage/local/lib/python2.7/site-packages/sage/graphs/graph.pyc
in chromatic_number(self, algorithm)
2487 elif algorithm == "MILP":
2488 from sage.graphs.graph_coloring import vertex_coloring
-> 2489 return vertex_coloring(self, value_only=True)
2490 # another algorithm with bad performance; only good for
small graphs
2491 elif algorithm == "CP":
/home/ncohen/.Sage/local/lib/python2.7/site-
packages/sage/graphs/graph_coloring.pyc in vertex_coloring(g, k,
value_only, hex_colors, solver, verbose)
342 # tries to color the graph, increasing k each time it
fails.
343 tmp = vertex_coloring(g, k=k, value_only=value_only,
--> 344 hex_colors=hex_colors,
verbose=verbose)
345 if tmp is not False:
346 if value_only:
/home/ncohen/.Sage/local/lib/python2.7/site-
packages/sage/graphs/graph_coloring.pyc in vertex_coloring(g, k,
value_only, hex_colors, solver, verbose)
431 # a vertex has exactly one color
432 [p.add_constraint(Sum([color[v][i] for i in xrange(k)]),
min=1, max=1)
--> 433 for v in g.vertices()]
434 # adjacent vertices have different colors
435 [p.add_constraint(color[u][i] + color[v][i], max=1)
TypeError: integer argument expected, got float
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12389>
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