PetscGatherMessageLengths#
Computes information about messages that an MPI rank will receive, including (from-id,length) pairs for each message.
Synopsis#
#include "petscsys.h"
PetscErrorCode PetscGatherMessageLengths(MPI_Comm comm, PetscMPIInt nsends, PetscMPIInt nrecvs, const PetscMPIInt ilengths[], PetscMPIInt **onodes, PetscMPIInt **olengths)
Collective, No Fortran Support
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 lengthilengths
[i]
Output Parameters#
onodes - list of ranks from which messages are expected
olengths - corresponding message lengths
Notes#
With this info, the correct MPIU_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 nrecvs
, one can use PetscGatherNumberOfMessages()
See Also#
PetscGatherNumberOfMessages()
, PetscGatherMessageLengths2()
, PetscCommBuildTwoSided()
Level#
developer
Location#
Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages