Help with random numbers

[fishytiger]

I am trying to produce random numbers by using the FORTRAN commands:

call RANDOM_SEED(DATE_TIME(8))
call RANDOM_NUMBER(HARVEST=X)

but each time i run the program, I get the same set of numbers, any idea how to produce different set of numbers at every time?

Fishyiger

 

[fishytiger]

Hey!, I just learned the built in fortran random subroutine is pseudorandom,
thanks for the help tough!,

The best approach is to build onew own random generator!

fishy

 

[xwb]

I normally use the following: it is a variant of the one from

http://www.psc.edu/~burkardt/src/fftpack/fftpack.f90.

He moans a lot about the lack of randomness but it appears to be OK on my system

subroutine random_initialize ( )
  integer date_time(8), i, seed, seed_size
  integer, allocatable :: seed_vec(:)
  real t
!
!  Get the seed size
   call random_seed (size = seed_size)
!
!  Allocate space for the seed
   allocate (seed_vec(seed_size))
!
!  Get the current date and time.
   call date_and_time (values = date_time)
!
!  Construct a seed from the date/time
   seed = 0
   do i = 1, 8
      seed = ieor (seed, date_time(i))
   end do
!
!  Create a seed
   do i = 1, seed_size
      seed_vec(i) = ieor (seed, i)
   end do
!
!  Set the random number seed value.
   call random_seed (size = seed_size, put = seed_vec(1:seed_size))
!
!  Free up the seed space.
   deallocate (seed_vec)
   return
end subroutine random_initialize
!
! Test it
program main
   real t
   integer i
   call random_initialize ()
   do i = 1, 10
      call random_number (harvest = t)
      write (*,*) t
   end do
end program main