program main

c*********************************************************************72
c
cc MAIN is the main program for L1_NORM.
c
      include 'omp_lib.h'

      integer n
      parameter ( n = 1000 )
 
      integer i
      integer num_threads
      integer seed
      double precision wtime
      double precision wtime1
      double precision wtime2
      real x(n)
      real x_l1_norm

c$omp parallel
      num_threads = omp_get_num_threads ( )
c$omp end parallel

      write ( *, * ) ' '
      write ( *, * ) 'L1_NORM'
      write ( *, * ) '  FORTRAN77 version'
      write ( *, * ) '  Number of threads is ', num_threads
c
c  Set X to random values.
c
      seed = 11857
      do i = 1, n
        x(i) = real ( seed ) / real ( 16384 )
        seed = mod ( 3125 * seed, 16384 ) 
      end do
c
c  Compute norm sequentially.
c
      wtime1 = omp_get_wtime ( )
      x_l1_norm = 0.0
      do i = 1, n
        x_l1_norm = x_l1_norm + abs ( x(i) )
      end do
      wtime2 = omp_get_wtime ( )
      wtime = wtime2 - wtime1

      write ( *, * ) ' '
      write ( *, * ) 'Sequential calculation:'
      write ( *, * ) '  L1_NORM = ', x_l1_norm
      write ( *, * ) '  Time =    ', wtime
c
c  Compute norm using OpenMP loop.
c
      wtime1 = omp_get_wtime ( )
      x_l1_norm = 0.0
c$ omp parallel shared ( x ) private ( i ) reduction ( + : x_l1_norm )
c$ omp do
      do i = 1, n
        x_l1_norm = x_l1_norm + abs ( x(i) )
      end do
c$ omp end do
c$ omp end parallel
      wtime2 = omp_get_wtime ( )
      wtime = wtime2 - wtime1

      write ( *, * ) ' '
      write ( *, * ) 'Parallel calculation:'
      write ( *, * ) '  L1_NORM = ', x_l1_norm
      write ( *, * ) '  Time =    ', wtime

      stop
      end