[mpich-discuss] Active loop in MPI_Waitany?

[Jeff Hammond]

Seems obvious that Waitany spins on the array of requests until one
completes. Is that an active loop by your definition?

Jeff

On Thursday, July 30, 2015, Dorier, Matthieu <mdorier at anl.gov> wrote:

> Hi,
>
> I have a code that looks like this:
>
> while(true) {
>    do some I/O (HDF5 POSIX output to a remote, parallel file system)
>    wait for communication (MPI_Waitany) from other processes (in the same
> node and outside the node)
> }
>
> I'm measuring the energy consumption of the node that runs this process
> for the same duration, as a function of the amount of data written in each
> I/O operation.
> Surprisingly, the larger the I/O in proposition to the communication, the
> lower the energy consumption. In other words, the longer I wait in
> MPI_Waitany, the more I consume.
>
> Does anyone have a good explanation for that? Is there an active loop in
> MPI_Waitany? Another reason?
>
> Thanks!
>
> Matthieu
>


-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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