#17132: Perfect Matchings for Graphs
-------------------------------------+-------------------------------------
Reporter: ayyer | Owner:
Type: task | Status: new
Priority: minor | Milestone: sage-6.4
Component: graph theory | Resolution:
Keywords: perfect | Merged in:
matchings, graphs | Reviewers:
Authors: Arvind Ayyer | Work issues:
Report Upstream: N/A | Commit:
Branch: | 6091b96904f172d6aea9e4926cb14257850c77ea
public/ayyer/perfect_matchings | Stopgaps:
Dependencies: |
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Comment (by vferay):
Replying to [comment:13 ayyer]:
> If I first force it to be a tuple, I get another error
> {{{
> sage: [PerfectMatching(tuple(p)) for p in PM]
>
---------------------------------------------------------------------------
> TypeError Traceback (most recent call
last)
> <ipython-input-12-a67059f6b75f> in <module>()
> ----> 1 [PerfectMatching(tuple(p)) for p in PM]
>
> /Applications/Sage-6.2.app/Contents/Resources/sage/local/lib/python2.7
/site-packages/sage/misc/classcall_metaclass.so in
sage.misc.classcall_metaclass.ClasscallMetaclass.__call__
(build/cythonized/sage/misc/classcall_metaclass.c:1282)()
>
> /Applications/Sage-6.2.app/Contents/Resources/sage/local/lib/python2.7
/site-packages/sage/combinat/perfect_matching.pyc in
__classcall_private__(cls, p)
> 182 if len(objects) < 2*len(data):
> 183 raise ValueError("%s is not a valid perfect
matching:\n"
> --> 184 "there are some repetitions" %
p)
> 185 # Second case: p is a permutation or a list of integers,
we have to
> 186 # check if it is a fix-point-free involution.
>
> TypeError: not all arguments converted during string formatting
> }}}
> Can someone take a look?
Hi Arvind,
the bug comes from the perfect matching library: when elements of the base
set are themselves pairs of integers, the function 'flatten' goes too
far... I guess that adding the optional argument 'max_level=1' to all
'flatten' functions in the PerfectMatching library should solve the
problem.
Now the question is (perhaps for Nathan): should that be a separate post
on the trac/patch ?
I have another question : for the moment, you return perfect matchings as
a list of pairs. Mathematically, I think it is more logical to treat it as
a set of sets (two perfect matchings which differ by a permutations of the
pairs are equal). But perhaps turning it into a set in sage would imply
unnecessary copies/tests, so I wonder what is the best choice...
Best,
Valentin
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Ticket URL: <http://trac.sagemath.org/ticket/17132#comment:16>
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