[gate-users] Random seed

[Dirk Kruecker]

Dear Martin,

What do you want to achieve? Do you want to get exactly the same
set of events? This is impossible if you change your setup. At some point the 
simulation will differ since it has to simulate the difference in your design 
and it will consume a different amount of random numbers.

?

Best Regards

Dirk

> Hello GATE users,
> We are having trouble with the random seed in GATE. We are developing a PET
> system with two different detectors, and we therefore run GATE twice with
> the same seed. The first time we attach detector type #1 as crystalSD, and
> detector type #2 as phantomSD, and in the second run - with the same seed
> - we switch the crystalSD and phantomSD for the detectors. This produces
> two output (singles) files which we later sort into sinograms. This
> approach is working with the exception of producing original data in
> different runs. If we subtract sinograms from two different runs (with
> different seeds) from each other, it turns out that all events, except for
> a few hundred, are identical. 
> We have tried several different approaches to getting original data. One
> approach is running a short dummy program, and copying the endOfRun.rndm
> file onto our random-file and then running GATE (both times) with :
> /gate/output/root/setSaveRndmFlag 0
> /random/resetEngineFrom beginOfRunDummy.rndm
>
> We have also tried setting "/gate/output/root/setSaveRndmFlag 1" for the
> first run, and copying beginOfRun.rndm onto our random file for the second
> simulation, but that doesn't produce correlated data. Does anybody have an
> idea of how to solve this problem?
> Sincerely,
> Martin Janecek