Hi all,
As a collateral effect of the discovery of the new Mersenne prime, it
has pointed out we need of a very fast double-checker. I begun to study
the upcoming standard OpenMP and tried to make Glucas multithreaded.
I did it, and it runs well in the few systems available to me. I called
this Glucas's version as Glucasmp. The problem here is to find OpenMp
complain compilers, and multiprocessors systems to test.
So far, I wrote an OpenMP v.1.0 compatible. I also wrote code for Sun
WorkShop v.6.0 (here using specific Sun directives, similar to OpenMP).
These are some results:
System Compiler OS %CPU %Speed
4-Itanium @800 Mhz Intel-C v.5.1 RedHat 7.1 320% 250%
4-Pentium3 @500 Mhz Intel-V v.5.1 Debian 2.2 400% 335%
4-ev6@500 Mhz Compaq-C Tru64 Unix 400% 340%
2-Ultraii @450 Mhz SunWspro v 6.0 Solaris 200% 170%
Column 5 is the performance with respect the single processor version
using the same compiler/options. The FFT runlength is 768K. As we can
expect, small FFT runlengths are less suitable to multithreading than
very big FFT. Around 2048K FFTs the speed performance increases about
5-10%.
There is no OpenMP version for GNU/gcc :(. (A direct Posix threads code
is the alternative for gcc, but it is harder to implement)
It is still an experimental version. Here is when I need a help. If
anybody has access to more powerful systems with C-compilers that
understand OpenMP directives (or Sun MP), he could try to make and test
Glucasmp.
The code is at sourceforge:
http://glucas.sourceforge.net/QAdir/Glucas-2.8d.pre1.tar.gz
To build the binaries for Alphas or Sun/Solaris it is better to use the
special Makefiles 'Makefile.alpha_mp' or 'Makefile.sunc_mp' I used in my
tests, but we also need to edit those files to adapt them to our
systems.
Please, contact me in private e-mail for any question or suggestion.
Regards.
Guillermo.
P.D. Don't be excited those GIMPSers with SMP systems. It is better to
run N single processor clients than a Multithreaded N-procesors one. We
will get more credit with the single solution. Glucasmp (or Prime95mp)
should be useful when we want to make a special L-L test quickly (in a
QA work or after a new prime discovery)
--
Guillermo Ballester Valor
[EMAIL PROTECTED]
Granada (Spain)
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