! This file created from test/mpi/f77/coll/exscanf.f with f77tof90

! -*- Mode: Fortran; -*-

!

!  (C) 2003 by Argonne National Laboratory.

!      See COPYRIGHT in top-level directory.

!

      subroutine uop( cin, cout, count, datatype )

      use mpi_f08

      integer cin(*), cout(*)

      integer count

      TYPE(MPI_Datatype) datatype

      integer i

      if (datatype .ne. MPI_INTEGER) then

         write(6,*) 'Invalid datatype passed to user_op()'

         return

      endif

      do i=1, count

         cout(i) = cin(i) + cout(i)

      enddo

      end

!

      program main

      use mpi_f08

      integer inbuf(2), outbuf(2)

      integer ans, rank, size

      TYPE(MPI_Comm) comm

      integer errs, ierr

      TYPE(MPI_Op) sumop

      external uop

      errs = 0

      call mtest_init( ierr )

!

! A simple test of exscan

      comm = MPI_COMM_WORLD

      call mpi_comm_rank( comm, rank, ierr )

      call mpi_comm_size( comm, size, ierr )

      inbuf(1) = rank

      inbuf(2) = -rank

      call mpi_exscan( inbuf, outbuf, 2, MPI_INTEGER, MPI_SUM, comm,  &

      &                 ierr )

! this process has the sum of i from 0 to rank-1, which is

! (rank)(rank-1)/2 and -i

      ans = (rank * (rank - 1))/2

      if (rank .gt. 0) then

         if (outbuf(1) .ne. ans) then

            errs = errs + 1

            print *, rank, ' Expected ', ans, ' got ', outbuf(1)

         endif

         if (outbuf(2) .ne. -ans) then

            errs = errs + 1

            print *, rank, ' Expected ', -ans, ' got ', outbuf(1)

         endif

      endif

!

! Try a user-defined operation

!

      call mpi_op_create( uop, .true., sumop, ierr )

      inbuf(1) = rank

      inbuf(2) = -rank

      call mpi_exscan( inbuf, outbuf, 2, MPI_INTEGER, sumop, comm,  &

      &                 ierr )

! this process has the sum of i from 0 to rank-1, which is

! (rank)(rank-1)/2 and -i

      ans = (rank * (rank - 1))/2

      if (rank .gt. 0) then

         if (outbuf(1) .ne. ans) then

            errs = errs + 1

            print *, rank, ' sumop: Expected ', ans, ' got ', outbuf(1)

         endif

         if (outbuf(2) .ne. -ans) then

            errs = errs + 1

            print *, rank, ' sumop: Expected ', -ans, ' got ', outbuf(1)

         endif

      endif

      call mpi_op_free( sumop, ierr )

!

! Try a user-defined operation (and don't claim it is commutative)

!

      call mpi_op_create( uop, .false., sumop, ierr )

      inbuf(1) = rank

      inbuf(2) = -rank

      call mpi_exscan( inbuf, outbuf, 2, MPI_INTEGER, sumop, comm,  &

      &                 ierr )

! this process has the sum of i from 0 to rank-1, which is

! (rank)(rank-1)/2 and -i

      ans = (rank * (rank - 1))/2

      if (rank .gt. 0) then

         if (outbuf(1) .ne. ans) then

            errs = errs + 1

            print *, rank, ' sumop2: Expected ', ans, ' got ', outbuf(1)

         endif

         if (outbuf(2) .ne. -ans) then

            errs = errs + 1

            print *, rank, ' sumop2: Expected ', -ans, ' got ',outbuf(1)

         endif

      endif

      call mpi_op_free( sumop, ierr )

      call mtest_finalize( errs )

      end