[Mpi-21] review of chapter 4
gabriel at [hidden]
Fri Mar 7 17:18:09 CST 2008
just a couple of minor comments to chapter 4 ( collective
communication). I apologize if some of the issues have already been
a) page 128, line 35: "MPI_Bcast broadcasts a message from the process
with rank root to all processes of the group, itself included."
I would suggest to modify the last part of the sentence to :"...,
itself included for intracommunicators" (or something similar), since
the statement does not make sense for inter-communicators, and we do not
distinguish at that point in the text the two types of communicators yet.
b) a similar issues arises for gather (page 130, line 1). E.g. the
sentence could be re-structured slightly to :"If comm is an
intracommunicator, each process....". The same issue for Gatherv (page
131, line 40).
c) I would suggest to extend the descriptions of the examples in section
4.6.1 to explicitly mentioning, that comm is an intracomm in those
examples. Similarly for the examples in section 4.7.1; section 4.8.1;
example 4.15 and 4.16 on page 154
d) In the examples 4.17, 4.18 and 4.19 on pages 157--159, the code
executes MPI_Comm_rank on MPI_COMM_WORLD, but the subsequent MPI_Reduce
( and the if myrank==root section) on 'comm'. This should probably be
the same communicator, else the code doesn't make sense. I suggest to
replace MPI_COMM_WORLD with comm, following the procedure of the
previous examples in that section; alternatively, we could add a line
with comm=MPI_COMM_WORLD, in order to get around the problem mentioned
in bullet c).
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