Newsgroups: comp.parallel
From: Werner@rus.uni-stuttgart.de (Andreas Werner)
Subject: Different Programs on Cray-T3D nodes ?
Organization: Comp.Center (RUS), U of Stuttgart, FRG
Date: 2 Mar 1995 15:52:38 GMT
Message-ID: <3ja72s$crv@usenet.srv.cis.pitt.edu>

I have a problem on the Cray T3D MPP system: I want to
start four different programs on several nodes of the
MPP system.

I could do this with network pvm, but then the processes 
are in different partitions and cannot communicate fast
with each other (pvm_channel or shmem).

What I actually need is e.g.

    - open a partition
    - start Program A on nodes 00-03  or  00-07
    - start Program B on nodes 04-07  or  08-15  
    - start Program C on nodes 08-23  or  16-47
    - start Program D on nodes 24-31  or  48-63

All these programs MUST be able to use fast communication.

On the Paragon this is no problem at all. You open a partition
and start the programs you want on the nodes you like. On the 
Cray at the moment the only possibility I see is to start a fat 
binary on all nodes, with each nodes wasting a whole lot of memory 
for some code that will never be executed. And there is only 64 MB 
on every node!

Is there any other way to solve my problem? I think my problem is
fairly general, because every real program (except benchmarks, of
course) has I/O parts which are best done asynchronously on seperate
nodes while the others carry on calculating. Parallel pipelining
programs (that's what I'm doing right now) need this too.

Having different programs on different nodes of an MPP is one
of the most fundamental things in parallel programming. If this
is not possible, the MPP system degrades to some kind of "modern
vector-processor" which may be one, but clearly isn't the only
way of parallel programming.

Andreas Werner


