Dear LAM List,
I wrote a program where (almost) all processes write to the same file.
The processes are diveded in groups. During the main loop, all groups
(and so
all processes) write to the file. During the last cycle only some of the
groups
do so.
I could open the file in MPI_COMM_WORLD for the main loop and reopen it
again in
a reduced communicator for the last run.
Or I can open the file in one communicator per group and just not write
for some
of the groups in the last run.
What's difference? Performance issues? The code looks nicer with
group-wise
communicators.
Thank you for your help.
Michael
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