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Command-line SETI use both processors?

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h0mersimps0n

Member
Joined
Mar 22, 2002
Hey guys, I'm running SETI on my DUAL PII 400 machine and noticed that it only runs one processors at 100%?

OK, so I was just sitting here thinking, if I added another instance of the command line running would it bump the first one on the first processor or use the second processor all by itself?

I just did it and turns out both CPU's are running at 100% now... Is this accurate? Is this the whole idea behind multiprocessing? Windows gives seti its own processor or just bumps the extra processing need to the overflow (second processor)...

sorry if this is a dumb question...
 
There are two ways to take advantage of a multi-processor system. First is if your software is written to use multilple threads then those threads can be shared bewteen the cpus and the work gets done faster. Second is the ability to run a program on each cpu simultaneously as you see with SETI. Now each OS that has smp ability handles this slightly differently but the OS will either share the threads with the cpus or if the program is not multi-threaded then it will assign programs to each cpu. Multiple cpus give better performance through one means or the other. Software that is written to be multi-threaded gives the best overall performance boost. Multi-tasking is much smoother on a smp system because the OS is able to share the jobs with the cpus. There is a diminishing return though as each additional processor requires a little more overhead to manage so the benefits do not scale perfectly. Meaning that 2 cpus will not give twice the speed of one and four will not give twice the speed of 2 etc.

EDIT: This simple explination in no way takes into account Intel's new technology called Hyperthreading. That is like having two cpus in one cpu...sort of. ;)

Most people do what you figured out and that is run a separate instance of SETI for each cpu. :)

Cy
 
The only problem is that SETI@home is not written to use a SMP setup. The only way that two (or more processors) help crunching is adding a new instance to crunch a different WU. SO if you have two processors you can run 2 WU at the same time with no penalty to the time involved.

If you are using the SETIDriver software you can use the maximum processes field to increase the number of units you are running. Other way is using the - N CPU modifier to the CLC to especify whcih CPU the CLC is running with. N starts in 0 and goes up to the maximum number of processor you have minus 1.
 
Yeah. I would suggest Driver as well. We had a dual setup we were messing with, and SetiDriver actually automatically set the number of max processes to two when it saw that there were two procs.
 
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