Re: [fluka-discuss]: MC error calculation

From: Stefan E. Mueller <stefan.mueller_at_hzdr.de>
Date: Fri, 15 Mar 2024 09:34:00 +0100 (CET)

Dear Amandeep Sharma,

the FLUKA postprocessing routines (either invoked from FLAIR's
"Process"-Button in the "Run"->"Data" menu, or using directly the
executables in $FLUPRO/flutil/*suw) use the Central Limit Theorem to
express the statistical uncertainty of the scorer result as the standard
deviation (sigma) of a normal distribution. For this, the postprocessing
routines need at least 5 independent FLUKA runs.

See e.g.

https://indico.cern.ch/event/753612/contributions/3121551/attachments/1974578/3285956/MC_2019.pdf
(slides 20ff)

As a (crude) rule of thumb, the simulation has converged if this
uncertainty is better then 5 percent.

All other uncertainties (often called "systematic uncertainties")
unfortunately have to be (gu)es(s)timated by the user.

Cheers,

         Stefan

--
Stefan E. Mueller
Department of Information Services and Computing - Computational Science
and Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf
Tel: +49 (0351) 260 3847
Stefan.Mueller_at_hzdr.de
http://www.hzdr.de
Vorstand: Prof. Dr. Sebastian M. Schmidt, Dr. Diana Stiller
Vereinsregister: VR 1693 beim Amtsgericht Dresden
On Thu, 14 Mar 2024, Amandeep Sharma wrote:
> Whether it represents the statistical uncertainity in results or it is
> different from statistical uncertainity? 
> Regards ! 
> 
> On Thu, 14 Mar, 2024, 10:15 pm Stefan E. Mueller, <stefan.mueller_at_hzdr.de>
> wrote:
>       Dear Imen Hammami,
>
>       judging from your screenshot, I would say that your uncertainty
>       is
>       on the order of 0.014% for all your results. No need to multiply
>       by 100.
>       These are already percentage errors.
>
>       Cheers,
>
>               Stefan
>
>       --
>       Stefan E. Mueller
>       Department of Information Services and Computing - Computational
>       Science
>       and Institute of Radiation Physics
>       Helmholtz-Zentrum Dresden-Rossendorf
>       Tel: +49 (0351) 260 3847
>       Stefan.Mueller_at_hzdr.de
>       http://www.hzdr.de
>
>       Vorstand: Prof. Dr. Sebastian M. Schmidt, Dr. Diana Stiller
>       Vereinsregister: VR 1693 beim Amtsgericht Dresden
>
>       On Thu, 14 Mar 2024, imen hammami wrote:
>
>       >  Hi, Could someone provide guidance on how to calculate the
>       Monte Carlo
>       > error from the output of the USRBIN card, given that we've
>       utilized 5*10^7
>       > primaries for 5 cycles to calculate the dose?  Do I need to
>       multiply the
>       > values in the red box by 100 to get the exact error value in
>       percentage? Any
>       > insights would be greatly appreciated. 
>       >
>       > Regards
>       >
>       >
>       >
>       >
>       >
>       >
>       > image.png
>       >
>       >
> 
> 
>

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Received on Fri Mar 15 2024 - 12:35:21 CET