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Subject: [OMPI users] [Fwd: mpi alltoall memory requirement]
From: vkm (viral.vkm_at_[hidden])
Date: 2009-04-22 03:10:01


Hi,
I am running MPI alltoall test on my 8nodes cluster. They all have
24core cpus.
So total number of processes that I am running is 8*24=192. In summary,
alltoall test on 8nodes and 24 processes per node.

But, my test consumes all RAM and swap space memory. However, if I count
required memory then calculation comes up as below.

Alltoall test runs max upto 4M datasizes. Each proc will have ONE
sendbuf and ONE recvbuf for all remaining 191 processes to talk(and one
to talk to itself).

So, on one node one process will need 192*4M = 768M memory for sendbuf.
Now, one one node there are in fact 24 process running. So on one node,
in total, I need 768M *24 = 18432M = ~18G for sendbuf

The same amount of memory required for recvbuf. So at the least each
node should have 36GB of memory.

Am I calculating right ? Please correct.