[gate-users] splitting a GATE simulation by TIME

[ludovic Ferrer]

Hello Qianmei,

>> to make sure that the results from different jobs are independed, 
>> what should i do?
>>
>> I tried to use the command
>> /random/resetEngineFrom endOFRun1.rndm  in job1
>> /random/resetEngineFrom endOFRun2.rndm  in job1
>> /random/resetEngineFrom endOFRun3.rndm  in job1
>> .....
>> so that the random number will be called from the different files. 
>> Then i changed the random numbers (from the second number in the 
>> endOfRun.rndm) in each file to make sure that random numbers in 
>> different file are different.

Changing the first number is not sufficient. In fact, the first number 
(the seed) is strongly connected to 97 subsequent random numbers. For 
more explanation have a look to CLHEP doc. So, doing so, you may have 
some troubles with the random sequence and you cannot be sure that all 
the random numbers are generated with a long period or with a flat 
uniform sequence.

>>  My question is: Am i right to doing so. If yes, how many random 
>> numbers i should change? I tried to change one random number and 
>> found out the random numbers from the endOfRun have changed 
>> completely from a short run.
>>

>> Can you explain the meaning of the first and last four numbers(c, 
>> cd,cm etc) in the endOfRun.rndm file to me, such as
>>
The first is the seed of the generator machine
the 97's numbers are the useful for the HepJamesRandom generator (used 
by default)
c, cd and cm are numbers that are used to calculate the random number.

So, to run your jobs onto different nodes, you should send to each node 
a file that looks like beginOfRun.rndm or endOfRun.rndm.
A possible trick is to generate those files beforehand and then send 
one file per node. This is the "official" trick and some  are doing so. 
I don't have personally  them.
And other trick is to modify the code and force Gate to generate the 
correct sequence of 97 numbers with the seed you gave ( in file 
containing the seed ).

To get the files I mentionned, you should write to Lydia Maigne.

Hope this help
Ludovic Ferrer
service de physique médical
Centre René Gauducheau
44805 St HERBLAIN
tel : 33 (0)240679954
fax : 33 (0)240679731