Newsgroups: comp.parallel.mpi
From: christal@imag.fr (Michel Christaller)
Subject: Re: MPI_Ibsend()
Organization: Institute IMAG, Grenoble, France
Date: 25 Jan 1996 21:39:12 GMT
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit
Message-ID: <4e8ta0$qb9@imag.imag.fr>

Eric Salo (salo@mrjones.engr.sgi.com) wrote:
: What exactly are the semantics of this very strange call? What does it
: mean for the request to be completed? I'm guessing that a completed
: request means that the data has been successfully copied into the
: user-provided buffer, but that doesn't appear to be significantly
: different behavior from MPI_Bsend().

It is significantly different if the message is huge. With sophisticated 
hardware (aka DMA), the copy can be done in background and the main processor
is free to do something else.

: I suppose maybe you could use this function to queue up buffered
: message requests? But in that case, calling MPI_Ibsend() when there is
: insufficient buffer space available would have to not be an error and
: I certainly couldn't find anything in the standard on that topic.

To my knowledge, one have to specify the size of the copy-buffer for
all buffered sends, always. MPI doesn't manage any buffer in your place
(it's one big difference from PVM).

: Comments?

: Eric Salo         Silicon Graphics Inc.             "Do you know what the
: (415)390-2998     2011 N. Shoreline Blvd, 7L-802     last Xon said, just
: salo@sgi.com      Mountain View, CA   94043-1389     before he died?"

--


-----------------------------------------------------------------------
Michel Christaller                   Campus Universitaire
                                     LMC, Institut Fourier, BP 53X
Michel.Christaller@imag.fr           100 Rue des Mathematiques
Tel: (33) 76 51 46 31                38041 Grenoble CEDEX 9, FRANCE
Fax: (33) 76 63 12 63
#######################################################################
TRY LINUX ! A FULL UNIX SYSTEM FOR FREE ! 
thanks to all those who contributed
#######################################################################


