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Unique random numbers series in fortran

I have this problem in Fortran where I need to generate a sequence of random numbers (precisely, 729 random numbers between 1 and 1000) and to do I use the intrinsic function random_number().

The problem, of course, is that it returns pseudorandom numbers and it happens to often that I get same values repeated. I'm not an expert in programming with Fortran, but how can I get 729 unique random numbers without repetitions? Can someone help me?

Solution

  • This shows how you can in an inelegant way solve your problem.

    program p
   implicit none
   integer, parameter :: n = 10
   logical :: a(n) = .false.
   integer b(n), cnt
   real x
   cnt = 1
   do
      call random_number(x)
      b(cnt) = n * x + 1
      if (.not. a(b(cnt))) then
         if (b(cnt) > n) cycle
         a(b(cnt)) = .true.
         cnt = cnt + 1
         if (cnt > n) exit
      end if
   end do
   print '(*(1X,I0))', b
end program p