fortran simple benchmark

      program prog

      implicit none

    integer, parameter :: x_min = -20, x_max = 20
    integer, parameter :: y_min = -20, y_max = 20
    integer, parameter :: z_min = -20, z_max = 20
    real(8), parameter :: step = 0.1_8

    real(8) :: r, sum
    real(8) :: x,y,z
    real(8) :: t0, t1

    call cpu_time(t0)
    r = 0.0_8
    sum = 0.0_8

    do x = x_min, x_max, step
        do y = y_min, y_max, step
            do z = z_min, z_max, step
                r = sqrt(x*x + y*y + z*z)
                sum = sum + sin(-r)*exp(-r)
            end do
        end do
    end do
    call cpu_time(t1)
    write(*,*) sum-1
    write(*,*) t1-t0
      end program prog