Code: SDSC T3E sample code, modified for MCS572F98 for multi-data and timing
*URL/original:<"http://www.psc.edu/general/software/cray/t3d/mpich/mpich.html">
c****************************************************************************
c   pi.f - compute pi by integrating f(x) = 4/(1 + x**2)     
c     
c   Each node: 
c    1) receives the number of rectangles used in the approximation.
c    2) calculates the areas of it's rectangles.
c    3) Synchronizes for a global summation.
c   Node 0 prints the result.
c
c  Variables:
c
c    pi  the calculated result
c    n   number of points of integration.  
c    x           midpoint of each rectangle's interval
c    f           function to integrate
c    sum,pi      area of rectangles
c    tmp         temporary scratch space for global summation
c    i           do loop index
c****************************************************************************
      program main

      include 'mpif.h'

      real*8  PI25DT
      parameter        (PI25DT = 3.141592653589793238462643)

      real*8  mypi, pi, h, sum, x, f, a
      integer n, myid, numprocs, i, rc
c
*  Wall Time Declarations:
        real*8       start, finish, totalwalltime, traperror
c

c              Statement function to integrate
      f(a) = 4./ (1.+ a*a)

      call MPI_INIT( ierr )
      call MPI_COMM_RANK( MPI_COMM_WORLD, myid, ierr )
      call MPI_COMM_SIZE( MPI_COMM_WORLD, numprocs, ierr )
      print *, 'Process# ',myid,' of ',numprocs,' processors is alive'

      n = -1
      sizetype   = 1
      sumtype    = 2
      
 10   if ( myid .eq. 0 ) then
      write(6,98)
98      format('Enter the number of intervals: (0 quits)')
        read(5,99) n
99      format(i10)
           if(n.lt.0) n=100
* Fall 98:  Wall Timer Added:
        start = MPI_WTIME(ierr)
      endif
      
      call MPI_BCAST(n,1,MPI_INTEGER,0,MPI_COMM_WORLD,ierr)

c                                 check for quit signal
      if ( n .le. 0 ) goto 30

c                                 calculate the interval size
      h = 1.0/n

      sum  = 0.0
      do 20 i = myid+1, n, numprocs
         x = h * (i - 0.5)
         sum = sum + f(x)
 20   continue
      mypi = h * sum

c                                 collect all the partial sums
      call MPI_REDUCE(mypi,pi,1,MPI_DOUBLE_PRECISION,MPI_SUM,0,
     $     MPI_COMM_WORLD,ierr)

c                                 node 0 prints the answer.
      if (myid .eq. 0) then
* Fall 98:  Wall Timer Added:
         finish = MPI_WTIME(ierr)
         write(6, 97) pi, 100*(pi - PI25DT)/PI25DT 
 97      format('  pi is approximately: ', F18.16,
     +          '  Relative Error is: ', E16.8)
         totalwalltime=finish - start
         write(6,400) totalwalltime, numprocs, n
400      format(' ','Integration Wall Time =',f9.6,' Seconds on',
     &    i4,' Processors for n =',i10)
      endif

      goto 10

 30   call MPI_FINALIZE(rc)
      stop
      end