SMP on multi-processor machines
 

Hi, I am just starting with GIMPS using OS/2 machine and so far so good. However, I have a couple of old servers with quad Zeons which I would prefer to use on this project.

I see from these pages that recommended use of dual processor machines is to run two instances of software. Is there a Linux version of the software which will run one instance on all four Xeons in SMP mode? (Not a computer specialist so please forgive if question is dumb!).
Regards,
Budgie.

hmmm, [URL="http://www.oxixares.com/glucas/"]glucas[/URL] comes to my mind :unsure:

[quote=Budgie;99301]Is there a Linux version of the software which will run one instance on all four Xeons in SMP mode?[/quote]

No, because the problem can not be easily parallelized. However, you can launch four copies of mprime by running it with the -B4 option.

Matt

[QUOTE=Budgie;99301]Is there a Linux version of the software which will run one instance on all four Xeons in SMP mode ?[/QUOTE]
Cruelty proposed to use GLucas: GLucas is far as efficient than Prime95 is. One should rather use GLucas on architectures where Prime95 is not available (Itanium2, Power, SPARC, ...).
GLucas is parallelized. But using 2, 4 or more threads is less efficient than running 2, 4 or more instances.
George has worked on a parallelized version of Prime95. If I remember well, he said that this feature is OK but George is not satisfied by the performance when the PC is not fully devoted to Prime95. As an example, running parallelized Prime95 on a quad Xeons is OK if only Prime95 is running on the machine, because any program consuming at least 1 CPU will prevent the four threads of Prime95 to make progress ...
Since, in your case, it seems you want to use the 4 Xeons machines for GIMPS project only, it would be worth for you to use the new version of Prime95 on these slow machines: better to loose 10% of performance than waiting 3 months before an exponent is tested, with the risk of losing the disk of FileSystem during this time.
The problem is that George still does not plan to deliver this parallelized version of Prime95 ... I would be very happy to experiment it !
Look at this [URL="http://www.mersenneforum.org/showpost.php?p=93559&postcount=24"]post[/URL] in this [URL="http://www.mersenneforum.org/showthread.php?t=5427"]thread[/URL].
Tony

Hi all and thanks very much for the helpful answers. I shall investigate options but IMHO a true multithreaded version of the software would be the best bet for the machines I have. Either for OS/2 or for 'nix would be fine. No M$ here.
Regards,
Budgie.

In the meantime you could run mprime quite easily one per processor by using the -A option. basically you have one folder with mprime. then just do:
./mprime -A0 -b
./mprime -A1 -b
./mprime -A2 -b
./mprime -A3 -b
You could specify that each processor gets a different type of assignment. I've found on dual processor/dual core machines that splitting the assignments as one processor doing LL, the other doing factoring is a good on machines where you don't have dual channel memory. run some benches as your performance may vary depending on your memory.

[quote=delta_t;99468]In the meantime you could run mprime quite easily one per processor by using the -A option. basically you have one folder with mprime. then just do:
./mprime -A0 -b
./mprime -A1 -b
./mprime -A2 -b
./mprime -A3 -b
You could specify that each processor gets a different type of assignment. I've found on dual processor/dual core machines that splitting the assignments as one processor doing LL, the other doing factoring is a good on machines where you don't have dual channel memory. run some benches as your performance may vary depending on your memory.[/quote]

Hi, this is where my profound ignorance shows up. Have downloaded mprime2414.tar.gz, uncompressed and tried the first line to start the first instance, alas I get no questions from PrimeNet and no work to do. I guess I have done something wrong but a clue would be appreciated.
Regards,
Budgie.

Show us the exact dialog of your interaction with the console.

[quote=Xyzzy;99558]Show us the exact dialog of your interaction with the console.[/quote]
Hi, now there's a question! I just entered the commands one at a time in the console and they ran, just like that. No dialogue, nothing.

I have checked the log files and all four instances are working as expected Computer IDs have been assigned but no user ID or password.

Just a thought, all machines are on same lan using same router and my OS/2 machine is running mprime all the time too. Could the PrimeNet server have recognised me somehow by virtue of this connection?

If I could locate these accounts on PrimeNet I could hopefully put them all under my ID but cannot see them there at present.

Any suggestions would be much appreciated.
Regards,
Budgie

They are running in the background then. Use "top" to view them. There are various controls in the shell to control them. I'd suggest setting up a cron job to start them and keep them running and set up an output file for each so you can see the progress. All of these have been covered here (somewhere) before.

Also, for each instance, you need to run:

./mprime -m

to set it up.

(Note: I've never set up a multiprocessor deal before.)