PetscBuildTwoSidedType

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

Level

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