#13668: MemoryError raised by WordMorphism.fixed_points method
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Reporter: slabbe | Owner: slabbe
Type: defect | Status: new
Priority: major | Milestone: sage-5.5
Component: combinatorics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Old description:
> The following bug was reported to me by Timo Jolivet last July 2012. It
> is still there is sage-5.3:
>
> {{{
> sage: s =
> WordMorphism({1:[1,2],2:[2,3],3:[4],4:[5],5:[6],6:[7],7:[8],8:[9],9:[10],10:[1]})
> sage: (s^7).fixed_points()
> [word: 122..., word: 2,3,4,...]
> sage: (s^7).reversal().fixed_points()
> MemoryError [...]
> }}}
New description:
The following bug was reported to me by Timo Jolivet last July 2012. It is
still there is sage-5.3:
{{{
sage: s =
WordMorphism({1:[1,2],2:[2,3],3:[4],4:[5],5:[6],6:[7],7:[8],8:[9],9:[10],10:[1]})
sage: (s^7).fixed_points()
[word: 122..., word: 2,3,4,...]
sage: (s^7).reversal().fixed_points()
MemoryError [...]
}}}
Also reported by Timo Jolivet in October 2012 the following hangs forever:
{{{
sage: s =
WordMorphism("1->321331332133133,2->133321331332133133,3->2133133133321331332133133")
sage: (s^2).fixed_points()
}}}
--
Comment (by slabbe):
In fact, this bugs comes from the `_fixed_point_iterator` method which
expand a possibly long word as a list :
{{{
#!python
sage: s =
WordMorphism({1:[1,2],2:[2,3],3:[4],4:[5],5:[6],6:[7],7:[8],8:[9],9:[10],10:[1]})
sage: s7 = s^7
sage: s7r = s7.reversal()
sage: M = matrix(s7r)^10
sage: max(flatten(map(list, M)))
274861440
sage: s7r10 = s7r^10
sage: it = s7r10._fixed_point_iterator(1)
sage: it.next()
Traceback (most recent call last):
...
in _fixed_point_iterator(self, letter)
1561 ('a', 1)
1562 """
-> 1563 w = list(self.image(letter))
1564 while True:
1565 for a in self.image(w.pop(0)):
MemoryError:
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13668#comment:2>
Sage <http://www.sagemath.org>
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