[Gate-users] problem with random number seed?

[surabhi balagopal nair]

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>
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>
>> *To:* hediye acun <acunhediye at yahoo.com>;
>> "gate-users at lists.opengatecollaboration.org"
>> <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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>> *From:*gate-users-bounces at lists.opengatecollaboration.org
>> [mailto:gate-users-bounces at lists.opengatecollaboration.org] *On Behalf
>> Of *hediye acun
>> *Sent:* Friday, January 29, 2016 3:46 PM
>> *To:* 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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