RE: Random seed (RANDOMIZE)

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Tue, 28 Jun 2011 10:34:47 -0700 (PDT)

Hi Chris,

reproducing a random number sequence may not be important for the
user, but is very important for whoever will have to debug a user
input after a crash.
The generator used in FLUKA is described in:
G. Marsaglia and W.W Tsang
The 64-bit universal RNG
Statistics& Probability Letters 66, 183-187 (2004)

I have not done myself tests as you suggest on that generator, but the authors
and plenty of other people have. Look up "The 64-bit universal RNG" on
Google and you will find many discussions about it.


On Tue, 28 Jun 2011, Chris Theis wrote:

> Alberto,
>> You can input any number you want: how can it be more flexible???
> from the user's point of view it would be more flexible if the user did not
> have to input different seeds but the program makes sure by itself that
> different runs are initiated with different values. The feature of
> reproducability, which is without any question important for development and
> sometimes also for a user, could be retained by specifically requesting it.
> Most of the time the user is not interested in reproducing the random number
> sequence and choosing a "good" seed is not necessarily trivial, depending on
> the mathematical details of the RNG implementation. By the way, did you ever
> investigate the influence of the chosen seeds on the cross-correlation and the
> period of the implemented RNG? In case you do have test results or some
> references for the one that is used I'd be interested and appreciate if you
> would be willing to share them with me.
> Cheers
> Chris
> -----Original Message-----
> From: [] On Behalf Of Alberto Fasso'
> Sent: 28 June 2011 16:03
> To:
> Cc: denis bertini
> Subject: Re: Random seed (RANDOMIZE)
> Denis,
> can you please explain what do you mean by "not particularly flexible"?
> You can input any number you want: how can it be more flexible???
> What is your purpose in setting a seed from a user routine?
> In any case any reference to function FLRNDM() changes the current random number. Is that what you want?
> Alberto
> On Tue, 28 Jun 2011, denis wrote:
>> Dear Fluka experts,
>> Could you tell me how to set a seed from a user fortran routine (
>> putting a number with RANDOMIZE in the input file being not
>> particularly flexible ) Thanks in advance,
>> Denis Bertini
Received on Wed Jun 29 2011 - 16:31:48 CEST

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