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Subject: [OMPI users] Broadcast and root process
From: giggzounet (giggzounet_at_[hidden])
Date: 2013-04-29 07:15:04


Hi,

I'm new on this list. I'm using MPI for years but I don't have written a
lot of code with MPI. Therefore is my question perhaps ridiculous:

I'm using a Computational Fluid Mechanics (CFD) Solver. This Solver uses
MPI to exchange the data between the different partitions. In this
solver the "root processor" is always the processor 1. So this proc
reads the input, broadcast a lot of things and writes the output.

During a time step the solver computes the reference pressure at a
point. This computation is done on a processor, which may not be the
root processor. Therefore after the computation a broadcast of the value
is necessary. For the moment in the code the broadcast is done with the
processor, where the reference pressure is computed, as root processor
(and not with the standard "root processor").

Is it false ? Must the root processor be the same during a computation
for all broadcasts ?

Best regards,
Guillaume