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Subject: Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS
From: jody (jody.xha_at_[hidden])
Date: 2010-04-26 02:25:15


Hi Asad

I must admit i don't know how one can find out whether extended precision
is being used or not.
I think one has to read up on the CPU's information.
I only know that most Intel 32bit-Processors use the extended precision
  http://en.wikipedia.org/wiki/X86
as does AMD Athlon
  http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/fpu_wp.pdf
but i think AMD Opteron does not.
But i am no expert in this area - i only found out about this when i
mentioned to someone
the differences in the results obtained from a 32Bit platform and a
64bit platform. Sorry.

Jody

On Mon, Apr 26, 2010 at 4:33 AM, Asad Ali <asad06_at_[hidden]> wrote:
> Hi Jodi,
>
>> I once got different results when running on a 64-Bit platform instead of
>> a 32 bit platform - if i remember correctly, the reason was that on the
>> 32-bit platform 80bit extended precision floats were used but on the 64bit
>> platform only 64bit floats.
>
> Could you please give me an idea as how to check this extended precision.
> Also I don't use float rather I use only double or long double.
>
> Cheers,
>
> Asad
> --
> "Statistical thinking will one day be as necessary for efficient citizenship
> as the ability to read and write." - H.G. Wells
>
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