petsc-3.4.5 2014-06-29


discovers communicating ranks given one-sided information, moving constant-sized data in the process (often message lengths)


#include "petscsys.h"  
PetscErrorCode PetscCommBuildTwoSided(MPI_Comm comm,PetscMPIInt count,MPI_Datatype dtype,PetscInt nto,const PetscMPIInt *toranks,const void *todata,PetscInt *nfrom,PetscMPIInt **fromranks,void *fromdata)
Collective on MPI_Comm

Input Arguments

comm - communicator
count - number of entries to send/receive (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)

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())


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

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


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

See Also

PetscGatherNumberOfMessages(), PetscGatherMessageLengths()

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