Newsgroups: comp.parallel.mpi
From: Jinsheng Xu <xujinshe@cps.msu.edu>
Subject: Re: MPI_Alltoall() on Cray T3D
Organization: Michigan State University, College of Engineering
Date: Sun, 10 Nov 1996 13:05:11 -0500
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Message-ID: <32861957.7882@cps.msu.edu>

N Sundar wrote:
> 
> MPI provides a call called MPI_Alltoall() that performs complete
> (all-to-all personalized) exchange. We are using it on the Cray T3D,
> which has an MPI implementation from EPCC, Edinburg (sp?), U.K.
> Does anybody out there know what algorithm is used by this
> implementation to perform all-to-all? Alternatively, are there any
> pointers to this?
> 
> Thanks in advance.
> Sundar.
> --
> ------------+----------------Disclaimer: These are my opinions only.
> N. S. Sundar!    I am ardently against all awkward, affected,
> GTA,CIS,OSU.!    arbitrary and aimless alliteration.
> INTJ        !    WWW: http://www.cis.ohio-state.edu/~sundar/

Good question. I also want to know whether this call is more
efficient than several send and receive calls which have
the same functionality as MPI_Alltoall(). 

MPI_Alltoall() call has many restrictions.
For example, send and receive buffer have to be continuous and
the receive message size has to be specified. It's very bad
if the receiver doesn't know the message size of the sender.

