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MathGroup Archive 2005

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Re: Multicore Calculations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60809] Re: [mg60769] Multicore Calculations
  • From: Jeff Bryant <jeffb at wolfram.com>
  • Date: Thu, 29 Sep 2005 05:41:25 -0400 (EDT)
  • References: <200509280541.BAA08344@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

   The results you get depend on a couple of factors.  I'll provide a 
couple comments and perhaps other, more qualified people can respond 
directly if necessary for additional details.

What platform (CPU and OS) are you running on? That will determine if
a) we support multiple processors/cores
and
b) if top shows threads independently  of their parent process.

Also, vector-vector (BLAS level 1) and matrix-vector operations (BLAS 
level 2) don't parallelize terribly well, so there will be little 
benefit to multiple processors for those types of operations, anyway.

-Jeff

Manuel Schmidt wrote:

> Hi all,
> 
> i'm wondering, how one can convince the MathKernel to do a numerical
> linear algebra calculation on two processors at the same time in 5.2.
> 
> Am I right, that this should be computed on two processors (if
> available):
> 
> vec1 = Table[Random[], {i, 5000000}];
> vec2 = Table[Random[], {i, 5000000}];
> 
> While[True,Dot[vec1, vec2]]
> 
> or a big matrix and a vector
> 
> matrix.vector;
> 
> Anyways, I see in top only one kernel running. There is only one thread.
> Are there different binaries for the multicore and the singlecore
> version?
> 
> Thanks,
> 
> Manuel
> 
> 


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