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

From Josip Almasi <joe@vrspace.org>
Newsgroups comp.lang.java.programmer
Subject Re: why running multiple instances of the same program is faster than running single instance?
Date 2014-06-03 09:40 +0200
Organization B.net Hrvatska d.o.o.
Message-ID <lmju57$m4j$1@gregory.bnet.hr> (permalink)
References <de5dcb91-d280-463d-86f9-3ffb658d391f@googlegroups.com>

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On 06/02/2014 05:12 PM, 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.

Maybe you're lucky, and read-ahead kicked in.
But I have no clue how to monitor this on linux.
I/O may be faster with multiple instances, either due to readahead, or 
due to dentry/inode caching.
Maybe slaptop and vmstat provide some useful info.

Regards...

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Thread

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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