#16475: Bug in Gomory-Hu tree algorithm
-------------------------------------+-------------------------------------
Reporter: foosterhof | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.3
Component: graph theory | Resolution:
Keywords: gomory hu tree | Merged in:
gomory-hu gomory_hu_tree | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | e4604fa9ba9cf8ef5475620ed6b3d156402015d6
u/foosterhof/ticket/16475 | Stopgaps:
Dependencies: #12797 |
-------------------------------------+-------------------------------------
Comment (by foosterhof):
In Graph.vertices():
{{{
if not boundary_first:
return sorted(list(self.vertex_iterator()), key=key)
}}}
Apparently, it is possible to compare Set and int (or sage.blabla.Integer)
objects, but not (frozen)set and int.
{{{
sage: Set([252,35]) < 1
True
sage: set([252,35]) < 1
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-16-ea79432632b4> in <module>()
----> 1 set([Integer(2352),Integer(2352)]) < Integer(1)
TypeError: can only compare to a set
sage: frozenset([2352,2352]) < 1
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-17-55b270cfd9be> in <module>()
----> 1 frozenset([Integer(2352),Integer(2352)]) < Integer(1)
TypeError: can only compare to a set
}}}
And thus, when doing:
{{{
R1 = vertices & frozenset(g1.vertices())
}}}
it gives a TypeError, as g1 contains a vertex that is a frozenset, namely
g1_v:
{{{
g1_v = frozenset(set2)
g2_v = frozenset(set1)
g1.add_vertex(g1_v)
g2.add_vertex(g2_v)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/16475#comment:10>
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