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From: Michael (mklus_at_[hidden])
Date: 2007-03-06 11:26:04


I have a section of code were I need to send 8 separate integers via
BCAST.

Initially I was just putting the 8 integers into an array and then
sending that array.

I just tried using MPI_PACK on those 8 integers and I'm seeing a
massive slow down in the code, I have a lot of other communication
and this section is being used only 5 times. I went from 140 seconds
to 277 seconds on 16 processors using TCP via a dual gigabit ethernet
setup (I'm the only user working on this system today).

This was run with OpenMPI 1.1.2 to maintain compatibility with a
major HPC site.

Is there a know problem with MPI_PACK/UNPACK in OpenMPI?

Michael