int MPI_Reduce(void*
operand, void* result, int count, MPI_Datatype datatype, MPI_Op op, int
root, MPI_Comm comm)
MPI_Reduce combines the operands stored in
*operand using operation op
and stores the result in *result on process
root. Both operand and result refer
to count memory locations with type datatype.
MPI Reduce must be called by
all processes in the communicator comm, and
count, datatype, and op must
be the same on each process.
among others, op may be
MPI_MAX Maximum
MPI_MIN Minimum
MPI_SUM Sum
MPI_PROD Product