c
c  Each process must use a different seed.
c
      seed = 123456789 + id
      q = 0.0D+00
      do sample = 1, sample_num
        call r8vec_uniform_01 ( dim_num, seed, x )
        q = q + f ( dim_num, x )
      end do
      q = q / dble ( sample_num )
      q_error = abs ( q - q_exact )

      write ( *, '(2x,i8,2x,i8,2x,i8,2x,f16.10,2x,g16.6)' ) 
     &  id, sample_num, dim_num, q, q_error
c
c  Have each process sent results to process MASTER for reduction
c  to final result.
c
      call MPI_Reduce ( q, q_total, 1, MPI_DOUBLE_PRECISION, MPI_SUM, 
     &  master, MPI_COMM_WORLD, ierr )