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Re: Enable multicore calculation ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88178] Re: Enable multicore calculation ?
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Sun, 27 Apr 2008 04:59:13 -0400 (EDT)
  • Organization: University of Bergen
  • References: <fuumac$877$1@smc.vnet.net> <fuv09k$eje$1@smc.vnet.net>

Michael Weyrauch wrote:
> Hello,
> 
>    I run some larger calculations on Linux with Mathematica 6.0.2.1 and 
> 8 cores essentially using NDSolve, and these calculations definitly use
> usually 4 cores without any interference from my side. Mathematica
> seems to detect the multicore environment automatically and the
> software acts then accordingly. In a sense I was (positively) surprised.
> 
>    However, not everything in Mathematica supports multicore, and it is
> my guess and partly my experience that it is mostly (maybe only) 
> numerical stuff which uses multicores.
> 

Dear Michael,

I do not have access to any multiprocessor machines which have 
Mathematica.  I am curious:  do functions like Map or Inner use multiple 
  processors (in principle it is easy to parallellize these)?  More 
generally, can those functions that call other Mathematica functions use 
more than one processor?  Or is this capability restricted to built-in 
operations that are implemented at a lower level than the Mathematica 
language (such as numerical linear algebra)?

Is it guaranteed that Map evaluates the elements of a list in order? 
What about misuses such as the following:

a = 123;
Map[(a = 100 + Mod[a, #]) &, {5, 6, 7, 8}];
a

(Actually this one must be pretty hard to parallellize even if there are 
no guarantees about evaluation order.)

Szabolcs


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