#10268: adding GiNaC method to simplify_rational
----------------------------+-----------------------------------------------
Reporter: bgoodri | Owner: burcin
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-4.6.2
Component: symbolics | Keywords:
Author: Ben Goodrich | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by bgoodri):
Replying to [comment:5 burcin]:
> Replying to [comment:4 bgoodri]:
> > And then a related question is why does gcd seem to hang?
> The `numeric::gcd()` method calls `sage.symbolic.pynac.py_gcd()`. See
here:
http://pynac.sagemath.org/hg/file/b233d9dadcfa/ginac/numeric.cpp#l2526 It
could be that our gcd() function doesn't work exactly like CLN's `gcd()`
function which is used originally by ginac. This would effect the
termination criteria used in the multivariate gcd code in ginac/pynac.
[[BR]]
Okay, I've been contributing to the confusion. Now I see what you meant:
When sage calls Pynac's normal() function, Pynac calls "its" gcd()
function, which is actually sage's gcd() function. So, all the calls to
gcd() are expected behavior, and the question becomes why doesn't Pynac
get them over with and terminate in 30 seconds like GiNaC does with the
CLN implementation of gcd()?
For reference when I switch on the statistics bookkeeping in the (latest)
GiNaC source:
{{{
goodr...@y560:/tmp$ time ginsh test.ginsh
ginsh - GiNaC Interactive Shell (ginac V1.5.8)
__, _______ Copyright (C) 1999-2010 Johannes Gutenberg University
Mainz,
(__) * | Germany. This is free software with ABSOLUTELY NO
WARRANTY.
._) i N a C | You are welcome to redistribute it under certain
conditions.
<-------------' For details type `warranty;'.
Type ?? for a list of help topics.
gcd() called 56331 times
sr_gcd() called 0 times
heur_gcd() called 1612 times
heur_gcd() failed 1 times
real 0m34.025s
user 0m33.245s
sys 0m0.602s
}}}
Okay, that is what is supposed to happen. With the current Pynac, I
interrupt after an hour and
{{{
sage: quit;
Exiting Sage (CPU time 62m29.29s, Wall time 64m3.75s).
gcd() called 57537 times
sr_gcd() called 19 times
heur_gcd() called 1936 times
heur_gcd() failed 19 times
}}}
So, it looks as if Pynac is hanging at or toward the end, and it
experiences many more failures in the heur_gcd() routine. I guess I should
be looking at the gcd heuristics then. Any ideas come to mind?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10268#comment:8>
Sage <http://www.sagemath.org>
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