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Subject: Re: [OMPI users] "self scheduled" work & mpi receive???
From: pooja varshneya (pooja.varshneya_at_[hidden])
Date: 2010-09-23 11:49:43


Hi Lewis,

On Thu, Sep 23, 2010 at 9:38 AM, Lewis, Ambrose J.
<AMBROSE.J.LEWIS_at_[hidden]> wrote:
> Hi All:
>
> I’ve written an openmpi program that “self schedules” the work.
>
> The master task is in a loop chunking up an input stream and handing off
> jobs to worker tasks.  At first the master gives the next job to the next
> highest rank.  After all ranks have their first job, the master waits via an
> MPI receive call for the next free worker.  The master parses out the rank
> from the MPI receive and sends the next job to this node.  The jobs aren’t
> all identical, so they run for slightly different durations based on the
> input data.
>
>
>
> When I plot a histogram of the number of jobs each worker performed, the
> lower mpi ranks are doing much more work than the higher ranks.  For
> example, in a 120 process run, rank 1 did 32 jobs while rank 119 only did 2.
>  My guess is that openmpi returns the lowest rank from the MPI Recv when
> I’ve got MPI_ANY_SOURCE set and multiple sends have happened since the last
> call.
>

What is the time taken by each computation ? It is possible that
computation time for longer tasks is much greater than computation
time for shorter tasks ?

>
>
> Is there a different Recv call to make that will spread out the data better?
>
>
>
> THANXS!
>
> amb
>
>
>
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