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Subject: [OMPI users] MPI_Bcast not broadcast to all processes
From: alireza ghahremanian (mat2ag_at_[hidden])
Date: 2007-12-05 04:08:20


Dear Friends,

I am writing a matrix multiplication program with MPI. MPI_Bcast does
not broadcast to all processes, in last iteration for block size
greater than a specific size. I test it with both MPICH and OPENMPI.I
have 12 processes which 7 of them are reached to MPI_Bcast but when
master (rank 0) send only 6 of them receive the broadcast (exactly from
rank 1 to 6) and rank 7 stays in waiting. Surprisingly this happen only
in iteration 3999 from 4000 and in the rest of cases every thing is all
right, also if I reduce the block size, which, will be sent, every
thing will be done correctly.

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