implicit real(8) (x-z)
  integer(8), parameter :: n= 10000000
  real(8)               :: t1 = 0.0, t2 = 0.0, t3 = 0.0
  real(8)               :: dt1
  real(4)               :: xin(1024), yin(1024), z(n)
  integer(8)            :: i, j, m

  xin = (/(dble(j),j=1,1024)/)
  yin = xin

  print '(a/a/)', "DOT_PRODUCT test", "   array length        time(ns)"
  do l = 2,10

    m = 2**l
    t1 = tim ()

    do i = 1, n
      z(i) = dot_product (xin(1:m), yin(1:m))
    end do

    t2 = tim ()

    do i = 1, n
      z(i) = 0d0
    end do

    t3 = tim ()

    dt1 = 1e9_8 * (2d0*t2 - t1 - t3) / (dble (n))
    print '(5x,i4,12x,f8.2,12x,f8.2)', m, dt1
  end do

contains

! Do not use secnds - various compilers do not support it.
  real(8) function tim ()
    character(12)         :: ddate, dtime, zone
    integer(4)            :: elems (8)
    call date_and_time (ddate, dtime, zone, elems)
    tim = 60.0_8 * elems(6) + elems(7) + 0.001_8 * elems(8)
  end function tim

  end