petsc-master 2015-11-27
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Computes info about messages that a MPI-node will receive, including (from-id,length) pairs for each message.


#include "petscsys.h"  
PetscErrorCode  PetscGatherMessageLengths(MPI_Comm comm,PetscMPIInt nsends,PetscMPIInt nrecvs,const PetscMPIInt ilengths[],PetscMPIInt **onodes,PetscMPIInt **olengths)
Collective on MPI_Comm

Input Parameters

comm - Communicator
nsends - number of messages that are to be sent.
nrecvs - number of messages being received
ilengths - an array of integers of length sizeof(comm) a non zero ilengths[i] represent a message to i of length ilengths[i]

Output Parameters

onodes - list of node-ids from which messages are expected
olengths - corresponding message lengths


With this info, the correct MPI_Irecv() can be posted with the correct from-id, with a buffer with the right amount of memory required.

The calling function deallocates the memory in onodes and olengths

To determine nrecevs, one can use PetscGatherNumberOfMessages()

See Also


Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages