# Fortran Wiki kiss64

A 64-bit KISS random number generator by George Margaglia, originally posted to comp.lang.fortran in the message 64-bit KISS RNGs. No license was specified.

This version was modified by Jason Blevins to use implicit none? and to portably declare the 64-bit/eight-byte integer type.

program test_kiss64
implicit none
integer, parameter :: i8b = selected_int_kind(18)  ! eight-byte integer
integer(i8b) :: i, t

do i = 1, 100000000
t = kiss64()
end do

if (t .eq. 1666297717051644203_i8b) then
print *, "100 million calls to KISS() OK"
else
print *, "Fail"
end if

contains

function kiss64()
integer(i8b), save :: x, y, z, c
integer(i8b) :: t, k, m, s, kiss64
data x, y, z, c &
/ 1234567890987654321_i8b, &
362436362436362436_i8b, &
1066149217761810_i8b, &
123456123456123456_i8b /
m(x,k) = ieor(x, ishft(x,k))  ! statement function
s(x) = ishft(x, -63)          ! statement function
t = ishft(x, 58) + c
if (s(x) .eq. s(t)) then
c = ishft(x, -6) + s(x)
else
c = ishft(x, -6) + 1 - s(x + t)
endif
x = t + x
y = m(m(m(y,13_i8b),-17_i8b), 43_i8b)
z = 6906969069_i8b * z + 1234567
kiss64 = x + y + z
end function kiss64

end program test_kiss64