[MPICH] MPICH 105, SUN NIAGARA dead in the water

[chong tan]

yes and no.  The same code achieved almost 4X performance improvement using nemesis on X86 running Linux, so comm cost is not as high as one would think.   26B is the combined count for both send and recieve on the master whose job is in  syncing all the slaves.  The packages are small,  packed or not packed, the overhead is there.  packing is not going to speed up the thing by more than 4X.

Don't have the number on how the sock comm cost will be on Linux.  On INTEL SMP, MPI memesis can handle more than 1 million send or recv per second.

tan

----- Original Message ----
From: Anthony Chan <chan at mcs.anl.gov>
To: chong tan <chong_guan_tan at yahoo.com>
Cc: mpich-discuss at mcs.anl.gov
Sent: Thursday, April 26, 2007 11:43:25 AM
Subject: Re: [MPICH] MPICH 105, SUN NIAGARA dead in the water


On Thu, 26 Apr 2007, chong tan wrote:

> shm/ssm  : dropped pacakge
> nemesis   : not supported
> socket     : works, but very-very-very-slow due to the number of communication.  In one test, with 26 billion send+recieve, 6 processes with MPI is more than 10X slower than uni-process  (uni-process takes 15 hours)

This is off from the original topic.  But your stated performance
suggests your app's ratio of communication/computation may be too high
to archieve good performance.  Does your message tend to be small and
frequent ?  If so, is it possible to combine them using MPI_Pack ?
(I believe that there are tools that can do that for you.)

A.Chan

>
>
> any suggestion ?
>
> thanks
>
> tan
>
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