[mpich-discuss] Active loop in MPI_Waitany?

[Dorier, Matthieu]

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
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