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Re: Enable multicore calculation ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88164] Re: Enable multicore calculation ?
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sun, 27 Apr 2008 04:56:38 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <fuumac$877$1@smc.vnet.net>

guerom00 wrote:

> I'm running Mathematica 6.0.2 on a MacPro with 8 cores. I've noticed
> that the kernel only uses 1 core=85 Is it possible to enable multicore
> calculations ?

By default, a regular version of Mathematica 6.0.2 for Mac OS X on Intel 
Mac uses its *multi-threading* capabilities [1].

Which means that some functions (mostly linear algebra) may use 
extensively more than one core at some point during a computation.

Which also means that only a small subset of Mathematica functions have 
natively multi-threading capabilities and one cannot write one's own 
parallel/multi-threaded functions with a regular version of Mathematica. 
To do so, depending of your needs and budget, several solutions are 
available from WRI [3, 4, 5].

So to see many cores used on oneâ??s multi-core system, one may try a 
singular value decomposition or compute eigenvalues on a large numeric 
matrix.

Your mileage may vary, but on my dual-core system, the SVD starts by 
using mostly only one core, then, after a while both core are used (as 
seen thanks to the Activity Monitor or the top command). On the other 
hand, the eigenvalues used mostly one core at a time (i.e. starts on one 
core, then switches to the other, then comes back to the first core).


Timing[
  SingularValueDecomposition[RandomReal[1, {3000, 3000}]];]

(* {105.685, Null} *)

Timing[Eigenvalues[RandomReal[1, {2500, 2500}]];]

(* {109.357, Null} *)

$Version

(* "6.0 for Mac OS X x86 (64-bit) (February 7, 2008)" *)


HTH,
Jean-Marc

[1] http://forums.wolfram.com/mathgroup/archive/2006/Apr/msg00708.html

[2] "Does Mathematica take advantage of multiple processors?"
http://support.wolfram.com/mathematica/systems/allplatforms/multipleprocessors.en.html

[3] "Wolfram gridMathematica"
http://www.wolfram.com/products/gridmathematica/

[4] "Wolfram Mathematica Parallel Computing Toolkit"
http://www.wolfram.com/products/applications/parallel/

[5] "Wolfram Mathematica Personal Grid Edition"
http://www.wolfram.com/products/personalgrid/


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