sage 4.7.2 incorrectly gives girth of 4 on this graph:
sage: H=Graph([(0, 1), (0, 3), (0, 4), (0, 5), (1, 2), (1, 3), (1, 4), (1, 6), (2, 5), (3, 4), (5, 6)])
sage: H.girth()
4
There is a cycle (0,1,3) and sage 4.3 and magma correctly return 3.
This bug is now patch http://trac.sagemath.org/sage_trac/ti... !
It was a funny one. I wish there was a GOTO statement in Python ;-)
Nathann
Ahahaah. Ok, I see... Funny bug. I will post a patch soon :-)
Nathann
Well, here's what sage-5.0-beta1 has to say on the instance :-p
sage: H=Graph([(0, 1), (0, 3), (0, 4), (0, 5), (1, 2), (1, 3), (1, 4), (1, 6), (2, 5), (3, 4), (5, 6)])
sage: H.girth()
4
sage: H.is_triangle_free()
False
It should notice it is saying something stupid, only it does not. Sage is not a very bright student :-p
Asked: 2012-01-20 06:50:42 +0100
Seen: 564 times
Last updated: Jan 25 '12
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I copied your code and Sage 4.6 returns 3.