Re: Random seed (RANDOMIZE)

Hi Alfredo,
Yes this is correct and you understood perfectly.
Regards,
Denis

On 6/29/11 4:47 PM, "Alfredo Ferrari"<alfredo.ferrari_at_cern.ch> wrote:

> ... Chris proposal is naive and un-workable, and against what whichever
> Monte Carlo does for godd reasons. Of course it would make it impossible
> to have subsequent cycles following the same sequence, debugging the code
> etc etc.
>
> Reproducibility and predictability of the random number sequence implies
> starting from a deterministically defined random seed. The code can in no
> way know which sequences/up to which point have been already used in the
> past for the same problem obviously.
>
> I believe Denis question is different, if I understand correctly he would
> like to have a way through a user routine to input something equivalent to
> what is now input in what(2) of RANDOMIZe? Am I correct?
>
> Ciao
> Alfredo
>
>
> +----------------------------------------------------------------------+
> | Alfredo Ferrari || Tel.: +41.22.76.76119 |
> | CERN-EN/STI || Fax.: +41.22.76.69474 |
> | 1211 Geneva 23 || e-mail: Alfredo.Ferrari_at_cern.ch |
> | Switzerland || |
> +----------------------------------------------------------------------+
>
> On Tue, 28 Jun 2011, Alberto Fasso' wrote:
>
>> 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.
>>
>> Alberto
>>
>> 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: owner-fluka-discuss_at_mi.infn.it
>>> [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Alberto Fasso'
>>> Sent: 28 June 2011 16:03
>>> To: fluka-discuss_at_fluka.org
>>> 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 Thu Jun 30 2011 - 18:47:51 CEST