In an mpi parallel code which of the following two is a better way:
1) Read the input data from input data files only by the master process
and then broadcast it other processes.
2) All the processes read the input data directly from input data files
(no need of broadcast from the master process). Is it possible?.
2 is certainly possible; whether it's any advantage depends too much
on your filesystem, size of data, etc. I'd expect 2 to be faster only
if your file setup is peculiar - for instance, if you can expect all
nodes to have the input files cached already. otherwise, with a FS
like NFS, 2 will lose, since MPI broadcast is almost certainly more
time-efficient than N nodes all fetching the file separately.
but you should ask whether the data involved is large, and whether
each rank actually needs it. if each rank needs only a different
subset of data, then reading separately could easily be faster.
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