petsc-3.11.4 2019-09-28
Report Typos and Errors


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


#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())


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.


1. -Hoefler, Siebert and Lumsdaine, The MPI_Ibarrier implementation uses the algorithm in Scalable communication protocols for dynamic sparse data exchange, 2010.

See Also

PetscCommBuildTwoSided(), PetscCommBuildTwoSidedF(), PetscGatherNumberOfMessages(), PetscGatherMessageLengths()




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