Re: Fortran, no RAN ?

On 6/17/2024 7:49 PM, Arne Vajhøj wrote:

But if RNDOM is REAL*4 then my guess would be:
 RAN_LONGER_CYCLE(SEED1, SEED2)
 Example:
        real*4 function ran2arg(seed1, seed2)
       implicit none
       integer*4 seed1, seed2
       integer*4 temp
       real*4 dummy
       temp = xor(seed1, seed2)
       ran2arg = ran(temp)
       seed1 = xor(ishc(seed1, 1), temp)
       seed2 = xor(ishc(seed2, -1), temp)
       end
 Disclaimer: I do not know if the cycle from this one is actual longer.

I did an experiment with start seeds 1234567 and 7654321.
I aborted after burning a little over 2 CPU hours.
No cycle detected after 1281 billion calls.
That doesn't prove that cycle will always be longer.
But it does not provide any basis for pessimism either.
Arne