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Re: Re: Illusory Multicore Support in 5.2?

  • To: mathgroup at
  • Subject: [mg66070] Re: [mg66041] Re: Illusory Multicore Support in 5.2?
  • From: "Pratik Desai <pratikd at>" <Antti.I.Penttila at>
  • Date: Fri, 28 Apr 2006 06:33:18 -0400 (EDT)
  • References: <> <e2pp8k$su2$> <>
  • Sender: owner-wri-mathgroup at

Antti Penttilä wrote:
> Pratik Desai wrote:
>> Try using SingularValueDecomposition on a sufficiently large matrix
>> Pratik
>> Wolfram Research, Inc.
>> Tech Support
> I have a new dual-core Athlon 64 X2 and WinXP 64-bit edition with 
> Mathematica 5.2. SingularValueDecomposition with a random 2000x2000 
> matrix takes about 41 seconds to complete but the processor load stays 
> around 50% all the time. It seems that we'll have to start getting some 
> refund of the price of Mathematica.
> Best regards,
> Antti Penttilä
Hello Antti

Mathematica 5.2 defaults to using only one thread for linear algebra on 
Windows. To use multiple threads and take advantage of multiple 
processors or cores, you will need to set OMP_NUM_THREADS to a value of 
% NUMBER_OF_PROCESSORS% in your environment. You can do this by going to 
My Computer and get to the properties template by right clicking and 
clicking Properties, click the Advanced Tab and then click on 
Environment Variables. Click on New right below the System Variables 
list. In the the variable name type in OMP_NUM_THREADS and variable 
value type in % NUMBER_OF_PROCESSORS%

Variable Name : OMP_NUM_THREADS

Now you can try your linear algebra operations. Dot on two matrices is 
the best indicator of your multiprocessing capabilities. If you have 
have further questions please let me know, or you can e-mail us directly 
at support at I apologize for any confusion.

Best regards,


Pratik Desai
Wolfram Research, Inc
Technical Support 

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