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Re: why running multiple instances of the same program is faster than running single instance?

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On 02/06/14 16:12, www wrote:
> Hi:
>
> We have a software(some code from ours and some from the 3rd party) doing scientific calculation. It runs for several hours for finishing two years calculation. We use linux and it has four CPUs. Our code is not con-current multi-threaded yet.
>
> We are puzzled that when we run multiple instances on the same linux computer, the run finishes earlier than running singe instance. When we run multiple instances, each instance is independently doing its own two year calculation. For example, one instance is calculating 1980-1981, another instance is calculating 1982-1983, etc. If running single instance for 1980-1981 takes 120 minutes to finish, when running together with other instances, it only needs 100 minutes to finish 1980-1981.
>
> Any suggestions why this is happening? Thank you very much.
>

Might it have something to do with the IO overhead of paging?

If you have a single process with a given amount of memory that runs for 
a long time then eventually some paging will occur.

If you have multiple processes with a (similar?) given amount of memory 
then there will be less need for paging, what happens if you increase 
the heap space of the single process (at least double) and reduce the 
heap space of the multiple processes (by half)

-- 
lipska the kat - treacherous feline.
Proudly nominated for IPOTY 2014 - LIGAF
GNU/Linux user #560883 - linuxcounter.net

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why running multiple instances of the same program is faster than running single instance? www <xsli2@yahoo.com> - 2014-06-02 08:12 -0700
  Re: why running multiple instances of the same program is faster than running single instance? Joerg Meier <joergmmeier@arcor.de> - 2014-06-02 23:59 +0200
    Re: why running multiple instances of the same program is faster than running single instance? Arivald <arivald_@AT_interia_DOT_.pl> - 2014-06-03 13:25 +0200
  Re: why running multiple instances of the same program is faster than running single instance? Josip Almasi <joe@vrspace.org> - 2014-06-03 09:40 +0200
  Re: why running multiple instances of the same program is faster than running single instance? lipska the kat <lipskathekat@example.com> - 2014-06-03 10:02 +0100
  Re: why running multiple instances of the same program is faster than running single instance? Rupert Smith <rupertlssmith@googlemail.com> - 2014-06-03 03:24 -0700
    Re: why running multiple instances of the same program is faster than running single instance? Rupert Smith <rupertlssmith@googlemail.com> - 2014-06-03 03:26 -0700
  Re: why running multiple instances of the same program is faster than running single instance? Roedy Green <see_website@mindprod.com.invalid> - 2014-06-06 19:50 -0700

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