petsc-3.8.4 2018-03-24

PetscCommBuildTwoSidedFReq

discovers communicating ranks given one-sided information, calling user-defined functions during rendezvous, returns requests

Synopsis

#include "petscsys.h"  
PetscErrorCode PetscCommBuildTwoSidedFReq(MPI_Comm comm,PetscMPIInt count,MPI_Datatype dtype,PetscMPIInt nto,const PetscMPIInt *toranks,const void *todata,
                                          PetscMPIInt *nfrom,PetscMPIInt **fromranks,void *fromdata,PetscMPIInt ntags,MPI_Request **toreqs,MPI_Request **fromreqs,
                                          PetscErrorCode (*send)(MPI_Comm,const PetscMPIInt[],PetscMPIInt,PetscMPIInt,void*,MPI_Request[],void*),
                                          PetscErrorCode (*recv)(MPI_Comm,const PetscMPIInt[],PetscMPIInt,void*,MPI_Request[],void*),void *ctx)

Collective on MPI_Comm

Input Arguments

	comm	- communicator
	count	- number of entries to send/receive in initial rendezvous (must match on all ranks)
	dtype	- datatype to send/receive from each rank (must match on all ranks)
	nto	- number of ranks to send data to
	toranks	- ranks to send to (array of length nto)
	todata	- data to send to each rank (packed)
	ntags	- number of tags needed by send/recv callbacks
	send	- callback invoked on sending process when ready to send primary payload
	recv	- callback invoked on receiving process after delivery of rendezvous message
	ctx	- context for callbacks

Output Arguments

	nfrom	- number of ranks receiving messages from
	fromranks	- ranks receiving messages from (length nfrom; caller should PetscFree())
	fromdata	- packed data from each rank, each with count entries of type dtype (length nfrom, caller responsible for PetscFree())
	toreqs	- array of nto*ntags sender requests (caller must wait on these, then PetscFree())
	fromreqs	- array of nfrom*ntags receiver requests (caller must wait on these, then PetscFree())

Notes

This memory-scalable interface is an alternative to calling PetscGatherNumberOfMessages() and PetscGatherMessageLengths(), possibly with a subsequent round of communication to send other data.

Basic data types as well as contiguous types are supported, but non-contiguous (e.g., strided) types are not.

References