[MPICH] Best way to time MPI_Allreduce

[Mehmet Belgin]

Hi,

I am trying to do some timing measurements with MPI_Allreduce. I get
different results from every processor, as expected. Should I use the
MPI_Barrier before and after the MPI_Allreduce call and then time it (which
will include the overhead of MPI_Barrier to the timing)? Or will it be
accurate if I simply get the maximum of the timing results I collected form
each processor.

Thank you so much in  advance,
Memo
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