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Subject: [OMPI users] MPI_Allreduce()
From: Brock Palen (brockp_at_[hidden])
Date: 2008-03-12 17:01:49

I have always been told that calls like MPI_Barrior() MPI_Allreduce()
and MPI_Alltoall() should be avoided.

I understand MPI_Alltoall() as it goes n*(n-1) sends and thus grows
very very quickly. MPI_Barrior() is very latency sensitive and
generally is not needed in most cases I have seen it used.

But why MPI_Allreduce()?
What other functions should generally be avoided?

Sorry this is kinda off topic for the list :-)

Brock Palen
Center for Advanced Computing