! bcastF.f90
! This program using MPI_BCAST (MPI Broadcast) to "broadcast" data - in this
! case PI - from the root process (processor 0) to all the other processors.
! Note that ALL of the processors have MPI_Bcast, not just the root process.
! One of the parameters in MPI_Bcast provides the numerical value of the root
! process.  In this program the root process is 'source', and it equals 0.
! This means that 0 is the root process sending the broadcast.  If the
! process is not 0, then it is receiving the broadcast from 0 (the 'source'
! parameter in MPI_Bcast).
! Make sure you see which parameter in MPI_Bcast represents the root process.

        program main
        include "mpif.h"

        double precision PI25DT
        parameter (PI25DT = 3.141592653589793238462643d0)
        double precision pi
        integer rank, size, count, source
        integer ierr, status(MPI_STATUS_SIZE)

        call MPI_INIT(ierr)
        call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
        call MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierr)

        count = 1;
        source = 0;
        if (rank .eq. source) then
                pi = PI25DT;
                print *, 'Rank ', rank, ' is broadcasting ', pi
        end if

        call MPI_BCAST(pi, 1, MPI_DOUBLE, source, MPI_COMM_WORLD, ierr)
        if (rank /= source) then
                print *, 'Rank ', rank, ' receives ', pi, &
                                ' from process ', source
        end if

        call MPI_FINALIZE(ierr)

        end program

! CRAY SV1:

! f90 bcast.c
! mpirun -np 8 a.out

! Rank  0  is broadcasting  3.14159265358979323846264300001E+0
! Rank  2  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  4  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  1  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  3  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  5  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  6  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  7  receives  3.14159265358978245785699378145E+0  from process  0

! mpirun -np 4 a.out

! Rank  0  is broadcasting  3.14159265358979323846264300001E+0
! Rank  2  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  3  receives  3.14159265358978245785699378145E+0  from process  0
! Rank  1  receives  3.14159265358978245785699378145E+0  from process  0