Changes between Version 1 and Version 15 of Ticket #15060
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 12/10/13 15:57:51 (6 years ago)
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Ticket #15060

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Ticket #15060 – Description
v1 v15 5 5 If my understanding of good terminology is correct, this should not be the case (see http://ncatlab.org/nlab/show/too+simple+to+be+simple ). Note that {{{Graph({}).is_tree()}}} correctly returns {{{False}}}. 6 6 7 Another issue is that7 Another issue is 8 8 {{{ 9 Graph({}).is_triangle_free() 9 sage: Graph({}).is_triangle_free() 10  11 ValueError Traceback (most recent call last) 12 <ipythoninput270aaa16d3aa5> in <module>() 13 > 1 Graph().is_triangle_free() 14 15 /usr/local/src/sage5.13.beta1/local/lib/python2.7/sitepackages/sage/graphs/graph.pyc in is_triangle_free(self, algorithm) 16 2287 B[v].add(map[u]) 17 2288 # map lengths 2 paths to bitsets 18 > 2289 BB = Bitset(capacity=N) 19 2290 for u in self.vertex_iterator(): 20 2291 BB.clear() 21 22 /usr/local/src/sage5.13.beta1/local/lib/python2.7/sitepackages/sage/misc/bitset.so in sage.misc.bitset.FrozenBitset.__cinit__ (sage/misc/bitset.c:5023)() 23 24 /usr/local/src/sage5.13.beta1/local/lib/python2.7/sitepackages/sage/misc/bitset.so in sage.misc.bitset.bitset_init (sage/misc/bitset.c:1256)() 25 26 ValueError: bitset capacity must be greater than 0 10 27 }}} 11 seems to allocate lots of RAM and possibly die with a MemoryError (it did so on the Sage cell server; on my machine I had to ctrlaltdel the VM). The culprit seems to be {{{Bitset(capacity=0)}}}. It looks like {{{is_triangle_free}}} is the only method ever using the {{{Bitset(capacity=X)}}} construction, so I'm not opening up a new ticket for this.