On Jul 4, 2:58 pm, David Harvey <[EMAIL PROTECTED]> wrote:
> On Jul 4, 2008, at 3:44 PM, Daryl Hammond wrote:
>
>
>
> > [EMAIL PROTECTED] ~]$ /home/daryl/sage-3.0.1/sage
> > ----------------------------------------------------------------------
> > | SAGE Version 3.0.1, Release Date: 2008-05-05 |
> > | Type notebook() for the GUI, and license() for information. |
> > ----------------------------------------------------------------------
>
> > sage: x = ZZ.random_element(2^2000000)
> > sage: y = ZZ.random_element(2^2000000)
> > sage: time z = x.xgcd(y)
> > CPU times: user 5.09 s, sys: 0.01 s, total: 5.11 s
> > Wall time: 5.13
> > sage: quit
> > Exiting SAGE (CPU time 0m5.14s, Wall time 1m9.74s).
> > [EMAIL PROTECTED] ~]$ /home/daryl/sage-3.0.2/sage
> > ----------------------------------------------------------------------
> > | SAGE Version 3.0.2, Release Date: 2008-05-24 |
> > | Type notebook() for the GUI, and license() for information. |
> > ----------------------------------------------------------------------
>
> > sage: x = ZZ.random_element(2^2000000)
> > sage: y = ZZ.random_element(2^2000000)
> > sage: time z = x.xgcd(y)
> > CPU times: user 95.05 s, sys: 0.02 s, total: 95.06 s
> > Wall time: 95.36 s
> > sage: quit
> > Exiting SAGE (CPU time 1m35.10s, Wall time 2m28.69s).
>
> Okay.
>
> What this probably means is that your sage 3.0.2 build is picking up
> a GMP from somewhere else entirely. The GMP shipped with sage has an
> asymptotically fast gcd routine, which is not present in vanilla GMP.
> The timings above suggest that the gcd in your 3.0.2 build is not
> asymptotically fast. (You could verify this by trying the same test
> above for say 2^4000000; if it was the sage version it should take
> about 190s, if it's the vanilla GMP version it should take about
> 380s.) If I was a unix guru I would know how to tell this directly,
> but this is best I could think of :-)
>
> So I suspect what happened is that when you messed around with the
> files in your sage-3.0.2 build, you somehow tricked sage into using a
> GMP from somewhere else. Again you could check this by rebuilding
> sage-3.0.2 from scratch (to be safe) and trying my previous
> multiplication speed test; if this theory is correct you should get
> the same times as for your 3.0.1 and 3.0.3 builds.
>
> Unfortunately this gets us back to square one, since it suggests that
> the original problem has nothing to do with GMP at all.
>
> Since no-one else is able to reproduce this problem, I can only think
> of two ways to proceed:
> (1) try by yourself to narrow down what is causing the slowdown. Find
> the simplest possible loop, or chunk of code, that illustrates the
> problem, maybe that will help us debug it via mailing list.
> (2) give someone here (e.g. me) remote access to your machine, so
> that we can try debugging it. I realise that may not be possible for
> various reasons.
>
> david
Here are the results for 2^4000000 (much as you predicted):
[EMAIL PROTECTED] ~]$ /home/daryl/sage-3.0.1/sage
----------------------------------------------------------------------
| SAGE Version 3.0.1, Release Date: 2008-05-05 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: x = ZZ.random_element(2^4000000)
sage: y = ZZ.random_element(2^4000000)
sage: time z = x.xgcd(y)
CPU times: user 12.83 s, sys: 0.11 s, total: 12.94 s
Wall time: 12.98
sage: quit
Exiting SAGE (CPU time 0m12.97s, Wall time 1m37.48s).
[EMAIL PROTECTED] ~]$ /home/daryl/sage-3.0.2/sage
----------------------------------------------------------------------
| SAGE Version 3.0.2, Release Date: 2008-05-24 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: x = ZZ.random_element(2^4000000)
sage: y = ZZ.random_element(2^4000000)
sage: time z = x.xgcd(y)
CPU times: user 409.23 s, sys: 0.06 s, total: 409.29 s
Wall time: 409.66 s
sage: quit
Exiting SAGE (CPU time 6m49.32s, Wall time 8m37.32s).
I will re-install sage-3.0.2 from source and re-run your tests.
I'll also attempt to narrow down the number of lines needed to produce
the problem I'm having.
Unfortunately my internet connection is dial-up AOL on a WinME box.
Thanks for all your help.
-Daryl
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