Re: Random seed (RANDOMIZE)

... I think I have a solution along what you want. However I want to check
it first to be sure...

I'll come back tomorrow.

                    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 Wed, 29 Jun 2011, denis wrote:

> 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 - 18:46:18 CEST