C
C   Test Problem 1 - - ** Np tasks <= 11 **
C
C   This program evaluates the trapezoidal rule estimate
C   for an integral of F(x). In this case, F(x) is exp(x)
C   evaluated for the interval of 0 to 1. Each case provides
C   2X increase in precision. Therefore each result should be
C   similar but, not the same.
C
C   Testing for Nps 1 ... 11 should execute programs.
C   Testing for Nps 12 and above should stop the program.
C
C   This program requires the following call(s)
C        MPI_INIT, MPI_COMM_RANK, MPI_COMM_SIZE, MPI_ABORT, MPI_FINALIZE

	program main 
        include 'mpif.h'
        PARAMETER (KASES=11)
        DIMENSION TN(KASES)
        DIMENSION TARRAY(2)
        INTEGER N(KASES)
        INTEGER nworkers, whoami
        DATA A / 0.0 /
        DATA B / 1.0 /
        DATA N / 100, 200, 400, 800, 1600, 3200,
     x        6400, 12800, 25600, 51200, 102400 /

C
C    Initialize environment
C
        call mpi_init(ierr)
        call mpi_comm_rank(MPI_COMM_WORLD, whoami, ierr)
        call mpi_comm_size(MPI_COMM_WORLD, nworkers, ierr)
        PRINT 100,nworkers,KASES
  100   FORMAT ('Environment allocated ', I6,' workers out of ', I6)

        if( whoami .GE. KASES ) then
            call mpi_abort(MPI_COMM_WORLD, ierr)
        endif
           whoami = whoami + 1
           H = (B-A)/(N(whoami))
           SUM = 0.0
           DO 10 I = 1, N(whoami)-1
              SUM = SUM+F(A+H*I)
   10      CONTINUE
        TN(whoami) = H*((F(A)+F(B))/2.+SUM)

           PRINT 30,A,B,whoami,N(whoami)
   30      FORMAT ('PROBLEM 1 WITH A,B,whoami,N = ',2F10.3,5X,I6,I6)
           PRINT 40,TN(whoami)
   40      FORMAT ('GIVES TN =',F10.6)

   60   FORMAT (F8.4,' USER, ',F8.4,' SYSTEM')

        call mpi_finalize(ierr)
        END
C
C
        FUNCTION F (X)
        F = EXP(X)
C	F = 4.0D0/(1.0D0+X*X)
        RETURN
        END