<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">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.</DIV>
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<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">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.<BR><BR>tan</DIV>
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<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">----- Original Message ----<BR>From: Anthony Chan <chan@mcs.anl.gov><BR>To: chong tan <chong_guan_tan@yahoo.com><BR>Cc: mpich-discuss@mcs.anl.gov<BR>Sent: Thursday, April 26, 2007 11:43:25 AM<BR>Subject: Re: [MPICH] MPICH 105, SUN NIAGARA dead in the water<BR><BR>
<DIV>On Thu, 26 Apr 2007, chong tan wrote:<BR><BR>> shm/ssm : dropped pacakge<BR>> nemesis : not supported<BR>> 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)<BR><BR>This is off from the original topic. But your stated performance<BR>suggests your app's ratio of communication/computation may be too high<BR>to archieve good performance. Does your message tend to be small and<BR>frequent ? If so, is it possible to combine them using MPI_Pack ?<BR>(I believe that there are tools that can do that for you.)<BR><BR>A.Chan<BR><BR>><BR>><BR>> any suggestion ?<BR>><BR>> thanks<BR>><BR>> tan<BR>><BR>> __________________________________________________<BR>> Do You Yahoo!?<BR>> Tired
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