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Subject: Re: [OMPI users] MPI-IO, providing buffers
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-12-19 11:07:31


No, sorry -- there are no "buffered" variants of the MPI_FILE_* functions like there are with point-to-point communications. So when you do MPI_FILE_WRITE (for example), it'll be directly using the buffer that you pass to it (which is almost always what you want, anyway -- "buffered" modes of communication just force an extra copy, and therefore potentially lower performance).

That being said, if you need an extra copy so that you can start a non-blocking file operation and then free the old buffer, then you can make a copy yourself and allow the original buffer to be freed.

On Dec 17, 2009, at 6:25 AM, Ricardo Reis wrote:

>
> Hi all
>
> I have a doubt. I'm starting using MPI-IO and was wondering if I can use
> the MPI_BUFFER_ATTACH to provide the necessary IO buffer (or will it use
> the array I'm passing the MPI_Write...??)
>
> many thanks,
>
> Ricardo Reis
>
> 'Non Serviam'
>
> PhD candidate @ Lasef
> Computational Fluid Dynamics, High Performance Computing, Turbulence
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>
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-- 
Jeff Squyres
jsquyres_at_[hidden]