petsc-3.10.5 2019-03-28
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# PetscBuildTwoSidedType

algorithm for setting up two-sided communication

### Synopsis

    typedef enum {
      PETSC_BUILDTWOSIDED_NOTSET = -1,
      PETSC_BUILDTWOSIDED_ALLREDUCE = 0,
      PETSC_BUILDTWOSIDED_IBARRIER = 1,
      PETSC_BUILDTWOSIDED_REDSCATTER = 2
      /* Updates here must be accompanied by updates in finclude/petscsys.h and the string array in mpits.c */
    } PetscBuildTwoSidedType;

     PETSC_BUILDTWOSIDED_ALLREDUCE - classical algorithm using an MPI_Allreduce with

         a buffer of length equal to the communicator size. Not memory-scalable due to

         the large reduction size. Requires only MPI-1.

     PETSC_BUILDTWOSIDED_IBARRIER - nonblocking algorithm based on MPI_Issend and MPI_Ibarrier.

         Proved communication-optimal in Hoefler, Siebert, and Lumsdaine (2010). Requires MPI-3.

     PETSC_BUILDTWOSIDED_REDSCATTER - similar to above, but use more optimized function

         that only communicates the part of the reduction that is necessary.  Requires MPI-2.

### See Also

PetscCommBuildTwoSided(), PetscCommBuildTwoSidedSetType(), PetscCommBuildTwoSidedGetType()

### Level

developer

### Location

include/petscsys.h
Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages