PetscGatherNumberOfMessages#

Computes the number of messages an MPI rank expects to receive during a neighbor communication

Synopsis#

#include "petscsys.h"  
PetscErrorCode PetscGatherNumberOfMessages(MPI_Comm comm, const PetscMPIInt iflags[], const PetscMPIInt ilengths[], PetscMPIInt *nrecvs)

Collective, No Fortran Support

Input Parameters#

comm - Communicator
iflags - an array of integers of length sizeof(comm). A ‘1’ in ilengths[i] represent a message from current node to ith node. Optionally NULL
ilengths - Non zero ilengths[i] represent a message to i of length ilengths[i]. Optionally NULL.

Output Parameter#

nrecvs - number of messages received

Notes#

With this info, the correct message lengths can be determined using PetscGatherMessageLengths()

Either iflags or ilengths should be provided. If iflags is not provided (NULL) it can be computed from ilengths. If iflags is provided, ilengths is not required.

Level#

developer

Location#

src/sys/utils/mpimesg.c

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