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From: George Bosilca (bosilca_at_[hidden])
Date: 2007-03-06 11:28:16


I doubt this come from the MPI_Pack/MPI_Unpack. The difference is 137
seconds for 5 calls. That's basically 27 seconds by call to MPI_Pack,
for packing 8 integers. I know the code and I'm affirmative there is
no way to spend 27 seconds over there.

Can you run your application using valgrind with the callgrind tool.
This will give you some basic informations about where the time is
spend. This will give us additional information about where to look.

   Thanks,
     george.

On Mar 6, 2007, at 11:26 AM, Michael wrote:

> 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
>
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