[Gate-users] problem with random number seed?
Andrej
andrej.studen at ijs.si
Mon Feb 1 17:08:25 CET 2016
A quick and dirty fix is to set the randomSeed to some run related
number. I know that in geant people would sometimes start each event
with a seed equal to that event number. Here you only have to do it
run-wise.
Cheers
Andrej
surabhi balagopal nair je 2/1/2016 ob 4:40 PM napisal:
> Hello,
>
> Can anyone tell me whether the Virtual Gate is built on GEANT4
> multithread ON or OFF?
>
> Thank you,
> SN
>
> On 1 February 2016 at 10:14, David Boersma
> <david.boersma at physics.uu.se <mailto:david.boersma at physics.uu.se>> wrote:
>
> Hi,
>
> It looks like Thomas Deschler was right: random number seeding in
> Gate (current develop version, but I suspect the conclusions also
> hold for release 7.1) only works correctly if the Geant4 10.1
> libraries were compiled with multithreading OFF. By "correctly" we
> mean: with "auto" seeding you get a different seed every time you
> run it, and therefore statistically independent outputs. If you
> use a geant4 installation built with multithreading=ON, then
> successive Gate runs will give identical outputs.
>
> We verified this (on Linux and on MacOSX) by compiling Geant4 with
> and without multithreading, and then building Gate with it. We ran
> Hediye's minimal RT macro (shoot electrons on a target foil, and
> collect a phasespace of the particles after it, stored in a ROOT
> output file). We ran the macro twice (renaming the output
> directory in between). "Ekine" histograms of the two runs were
> numerically identical when we ran *with* multithreading and they
> were clearly different *without* multithreading.
>
> Short term action item: it would be good to document this clearly
> in the README file and/or the 7.1 installation guide on the wiki.
>
> Medium/long term action item: fix Gate to work correctly with
> multithreaded geant4.
>
> I have more comments, but they are more technical, will submit
> them as "issues" on GitHub.
>
> HTH,
> David B.
>
>
> Den 01/02/2016 kl. 11:18, skrev hediye acun:
>
> Hello Loic,
>
> We tried your recommendations with David Boersma. First we
> run main
> macro file for 20 particles and stored output in PhS_new.root
> file. We
> got particle's properties(location and energy) in root with
> Scan command
> and then we closed root to make sure root will not remember
> the first
> output file due to the same tree's name. We run main macro
> second time
> with same particle number(20) to get second output file which
> called
> PhS_try.root. In root with scan we obtained particle's
> properties again
> for second run. After that we compared two text files which
> include
> particle's location and energies and there was no difference
> between them.
>
> David Boersma run same macro file in his computer which has Geant4
> compiled with multithread OFF, and he obtained different
> results for
> same number of primaries. My Geant4 compiled with multithread
> ON. We
> are going to try to compile on my computer with multitherad
> OFF and on
> David's computer multithread ON to investigate whether it
> really depends
> on the multithreading.
>
> Best regards.
>
> Hediye acun
>
> PS. It looks like the mailing list not working today. David didn't
> receive your reply and we didn't see on the archive either.
>
>
> ------------------------------------------------------------------------
> *From:* Grevillot Loic <loic.grevillot at medaustron.at
> <mailto:loic.grevillot at medaustron.at>>
> *To:* hediye acun <acunhediye at yahoo.com
> <mailto:acunhediye at yahoo.com>>;
> "gate-users at lists.opengatecollaboration.org
> <mailto:gate-users at lists.opengatecollaboration.org>"
> <gate-users at lists.opengatecollaboration.org
> <mailto:gate-users at lists.opengatecollaboration.org>>
> *Sent:* Monday, February 1, 2016 9:20 AM
> *Subject:* RE: [Gate-users] problem with random number seed?
>
> Hello,
> In my experience the command"/gate/random/setEngineSeed
> auto"works.
> In your example you are looking at histograms, but to verify
> that issue
> I was thinking about something different:
> -If the seed did not change as you suspect, the physical
> properties from
> every single particle stored in your Phase Space one after the
> other
> shall be exactly the same (position, direction, energy, etc.)
> for 2
> simulations.
> -Could you check that on a particle basis for 10 or 20 particles?
> You could even try a very simple example where you could
> randomly sample
> 10 particles and look if they are the same for 2 simulations.
> Let us know!
> Thanks
> Image:Uncle_Sam_pointing_finger_small.jpgImage:We-Need-You1-324x500.jpgImage:superdupont-we-need-you.jpgImage:gsam_want_gnu_small.jpg
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> *On Behalf
> Of *hediye acun
> *Sent:* Friday, January 29, 2016 3:46 PM
> *To:* gate-users at lists.opengatecollaboration.org
> <mailto:gate-users at lists.opengatecollaboration.org>
> *Subject:* [Gate-users] problem with random number seed?
> Hello All,
> I have Gate "develop" version and at the same time
> geant4.10.1.0 and
> root_v5.34.32 on the GPU. My operating system is Linux Mint 17.2 .
> I am triying to simulate a linac head to get Phase Space of
> photons.
> Just for an example I run Gate for a basic geometry which
> include only
> electron beam, target filter and Phase space plane inside a linac
> geometry. When I run Gate two or more times for same "number of
> primaries" I got the exactly the same Phase Space distributions
> (histogram of Ekine completely identical). But I am using
> "/gate/random/setEngineSeed auto" command and according to the
> documentation that should give me the different seed every
> time when I
> run it. I would expect some random differences between PhS's from
> different runs.
> Does anyone have any idea about this issue? Thank you in advance.
> Hediye Acun
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