#11994: Vertex separation and pathwidth in Sage
----------------------------+-----------------------------------------------
Reporter: ncohen | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.8
Component: graph theory | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author: Nathann Cohen
Merged: | Dependencies:
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Comment(by ncohen):
Oh ! I'll try to remember the "i in range()" thing, it just scares me to
use Python abstractions when I am in Cython, but if I can remember that it
is totally equivalent for Cython.. `:-)`
Oops, sorry about the bitsets... Yes, in earlier versions I tried to use
them but I found a workaround which improved the performances when using a
different data structure... I feel guilty when I don't use bitsets in an
enumerative code `:-)`
The important thing about the bitset function is the following : the best
is to use the __builtin_popcount() function from GCC when the processor
has the popcnt instruction (it is *really* faster), and this can be
enabled by adding
{{{
#cargs -mpopcnt
}}}
at the beginning of the code. On the other hand, when the processor does
not know this instruction the code crashes ("invalid instruction"). It'd
be great to "use this instruction when available", and this other short
code otherwise. This would really be GREAT `:-)`
Nathann
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11994#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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