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Subject: Re: What's the difference between NUMA, SMP and MPI for chess?

Author: Robert Hyatt

Date: 10:05:12 04/15/04

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On April 15, 2004 at 11:26:28, Joachim Rang wrote:

>On April 15, 2004 at 08:59:24, Robert Hyatt wrote:
>
>>On April 15, 2004 at 06:30:14, Joachim Rang wrote:
>>
>>>Hi,
>>>
>>>I read in the past of some differences between multiprocessor-Architectures
>>>between NUMA and SMP. Now I heard of something called MPI? Can enybody enlighten
>>>me what are the differences between this multiprocessor-Architectures(please not
>>>too technical) and what the main advantages/disadvantages for Chessengines?
>>>
>>>thanks in advance
>>
>>
>>SMP -> Symmetric MultiProcessing.  N cpus, all can do everything from handling
>>interrupts to initiating I/O.  Memory is shared.
>>
>>NUMA -> Non-Uniform Memory Access. Just like SMP except that each CPU has local
>>memory that can be accessed faster than memory on other processors.
>>
>>MPI -> Message Passing Interface.  It is a message passing library similar to
>>PVM that works mainly on clusters.  Those not knowing what they are doing might
>>use it on a NUMA box but it is not the best approach there.
>>
>>NUMA offers some problems in that it is more efficient for a CPU to access some
>>parts of memory than it is to access others.  If you don't plan for this, you
>>simply run slower than optimal.
>
>
>So for a chessengine a SMP-System is the best and a NUMA-System must be
>addressed with special code, right? MPI works for cluster but cluster are not
>efficient for chess because of latency and sharing problems, right?
>
>regards Joachim


You got it.  SMP is the easiest to use.  NUMA offers more processors
(scalability) but requires more programming effort and expertise.  Clusters take
this a step further with even larger scalability but _way_ more effort to use
it.




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