petsc-3.7.3 2016-08-01

PetscGatherMessageLengths

Computes info about messages that a MPI-node 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 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

Notes

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()

PetscGatherMessageLengths

Synopsis

Input Parameters

Output Parameters

Notes

See Also