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Subject: [OMPI users] shared memory (sm) module not working properly?
From: Nicolas Bock (nicolasbock_at_[hidden])
Date: 2010-01-15 17:47:16

Hello list,

I am running a job on a 4 quadcore AMD Opteron. This machine has 16 cores,
which I can verify by looking at /proc/cpuinfo. However, when I run a job

mpirun -np 16 -mca btl self,sm job

I get this error:

At least one pair of MPI processes are unable to reach each other for
MPI communications. This means that no Open MPI device has indicated
that it can be used to communicate between these processes. This is
an error; Open MPI requires that all MPI processes be able to reach
each other. This error can sometimes be the result of forgetting to
specify the "self" BTL.

  Process 1 ([[56972,2],0]) is on host: rust
  Process 2 ([[56972,1],0]) is on host: rust
  BTLs attempted: self sm

Your MPI job is now going to abort; sorry.

By adding the tcp btl I can run the job. I don't understand why openmpi
claims that a pair of processes can not reach each other, all processor
cores should have access to all memory after all. Do I need to set some
other btl limit?