Confusion with Uni and SMP clients

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Confusion with Uni and SMP clients

Postby elliott94 » Wed Sep 14, 2011 11:44 am

Hi everyone.

I've been reading through the various guides on the website, and am somewhat confused between the Uni and SMP clients.

My PC is using a dual-core processer, so at first I would have thought that I would need the SMP client. However, the Uniprocesser guide reads:

Do NOT lock cores to specific CPU: Turning this one will allow the client to use any free CPU/core on a multicore processor. If left unchecked, it will only use one core regardless if others are free or not.

If this is the case, what's the difference of the two clients?

I'm probably missing something obvious, but it seems a strange if the Uniprocesser client can support multiple cores anyway.

Thanks.

Elliott.
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Re: Confusion with Uni and SMP clients

Postby parkut » Wed Sep 14, 2011 12:59 pm

The Uniprocessor client will only utilize one core.

Launching a second uniprocessor client (in a different work directory) will utilize a 2nd core in a multi-core machine.

The SMP client recognizes how many cores you have and will utilize them all at the same time.
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Re: Confusion with Uni and SMP clients

Postby elliott94 » Wed Sep 14, 2011 1:33 pm

Hi, and thanks for your reply.

That makes sense. However, if that is the case, what is the purpose of the "Do NOT lock cores to specific CPU" checkbox, if only one core can be utalysed with the Uniprocesser version anyway?

Thanks again.
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Re: Confusion with Uni and SMP clients

Postby P5-133XL » Wed Sep 14, 2011 2:16 pm

The do not lock core option allows the uniprocessor core (and the GPU folding core) to float between multiple processor cores even though it is using at most a single processor core. Normal Windows behavior, will suspend a process when there is a higher priority process and then when the higher priority process is done it will unsuspend the lower priority process using whatever processor core is avail. When it is locked, then the folding core will stay attached to a specific processor core and not move around between processor cores i.e. no floating.

Generally you are better off not locking so that after being suspended, when any processor core becomes avail it will be taken rather than waiting for a specific processor core to become avail. That being said, there is a certain overhead that happens when switching a process between processor cores.
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Re: Confusion with Uni and SMP clients

Postby elliott94 » Wed Sep 14, 2011 2:52 pm

Hi, and thanks for your help.

In that case, would you say that I'd be better off simply running the SMP client if I've got 2 cores?

Cheers.
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Re: Confusion with Uni and SMP clients

Postby Jesse_V » Wed Sep 14, 2011 2:59 pm

elliott94 wrote:Hi, and thanks for your help.

In that case, would you say that I'd be better off simply running the SMP client if I've got 2 cores?

Cheers.


From the SMP Installation Guide: "The system must have a recent dual core processor or better to run this client with the -smp switch in SMP mode. Four cores or more are strongly recommended. This means older single core processors cannot run this client with the -smp switch, and older dual cores will not meet the very short work unit deadlines. If after running this client with the -smp switch on an older dual or an older quad core system, and the client does not meet the work unit preferred deadline, please remove the SMP client and replace it with one or more instances of the CPU client and/or GPU client."

So basically, unless you have a newer dual-core, you may not be able to get the work done fast enough. SMP has much shorter deadlines than uniprocessors, and will impact your system more, but it is more productive in terms of science throughput. IMHO, I'd think the uniprocessor is right for you, even two of them if you so want. Look in the uniprocessor guide how to install multiple instances of it.
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Re: Confusion with Uni and SMP clients

Postby ChasR » Wed Sep 14, 2011 3:25 pm

An Intel T7200 (C2D @ 2.0 GHz) meets all the deadlines with time to spare and makes about 1700 ppd on most of the WUs. If you have something faster than that and are running 24/7, you should have no problem running smp.
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