Implement a function for computing the number of messages received per MPI process #7145
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masterleinad
requested changes
Sep 4, 2018
include/deal.II/base/mpi.h
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| * destination more than once in their destinations list. | ||
| */ | ||
| unsigned int | ||
| compute_point_to_point_communications( |
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We usually prefix variables storing counts with n_. Hence, I think compute_n_point_to_point_communications would be a better name for this function.
source/base/mpi.cc
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| ++dest_vector[el]; | ||
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| # if DEAL_II_MPI_VERSION_GTE(2, 2) | ||
| // Find how many processes will send to this one |
source/base/mpi.cc
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| return n_recv_from; | ||
| # else | ||
| // Find how many processes will send to this one |
eldarkh
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@masterleinad I addressed your comments and added a |
masterleinad
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Sep 4, 2018
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/run-tests |
bangerth
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Sep 4, 2018
include/deal.II/base/mpi.h
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| * contains duplicate entries that means that multiple messages are | ||
| * intended for a given destination. | ||
| * | ||
| * @return A list of processors that have indicated that they want to send |
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This is no longer true. Can you update the return value description?
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@bangerth I made the change, thanks for pointing it out |
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Great, thanks @eldarkh ! |
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This pull request is to resolve #6954.
I implemented a new function that only computes the number of processes to expect communication from, without actually knowing what their ranks are. Currently in the library calls to
compute_point_to_point_communication_pattern()are always followed by using the size of the returned vector, so the actual pattern is never used.The implementation uses
MPI_Reduce_scatter_blockforMPIversions higher than 2.2, andMPI_Reducefollowed byMPI_scatterfor older version - as discussed in #6954 this speeds things up a bit.