how many processes is better?

Yixun Liu yxliu at
Thu Oct 26 19:17:33 CDT 2006

Thanks. I will read it:-)
  ----- Original Message ----- 
  From: Matthew Knepley 
  To: petsc-users at 
  Sent: Thursday, October 26, 2006 8:53 PM
  Subject: Re: how many processes is better?

  On 10/26/06, Yixun Liu <yxliu at> wrote:
    I want to know how many processes is better. My computer is dual processors PC with superthread. According to the exampe ex2 I set the problem domain to 800*200. I set the number of processes to 1,2,4,10 respecively and the runtime is 26, 19, 18, 15 respectively. How many processes is better. In my opinion 4(2processors * 2superthreads) is better based on my computer, but why 10 ran more quickly?

  Again, this question is about gneric theory of parallel processing, and really has not answer
  as you pose it. I suggest the book "Parallel Computing" by Grama, et. al. 




  "Failure has a thousand explanations. Success doesn't need one" -- Sir Alec Guiness 
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