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Forum: Event and Track Management
Re: Question Problem with TrackingAction::PostUserTrackingAсtion (Mark Chernikov)
Date: 16 Oct, 2017
From: Michael H. Kelsey <Michael H. Kelsey>

On Sun, 15 Oct 2017 16:22:53 GMT, Mark Chernikov wrote:
> Why the tracks of all particles in the
> TrackingAction::PostUserTrackingA&#1089;tion are called once, but
> specifically for the electron its track is called several times? The
> task is as follows: I pass the gamma through the Cherenkov radiator. As
> a result of the interaction of gammas with the radiator material Compton
> electrons are formed and the speed of some of them exceeds the speed of
> light in the medium. It is necessary to find the points of formation of
> those Compton electrons that formed at least one Cherenkov photon. I do
> it in the TrackingAction::PostUserTrackingA&#1089;tion. But why exactly
> the tracks of those electrons that gave the secondary photons then are
> called into the TrackingAction more than once? It causes a secondary
> recording of the same coordinate in output file and gives me wrong
> histogram. An example is taken as a basis: /extended/optical/OpNovice.
> Geant version: 4.10.03.p02. Thank you.

That is done because for optical physics, there can be so many (thousands or tens of thousands) new tracks created that the "stack" of tracks would become very large and introduce memory show downs (cache misses, paging, etc.). So the optical physics processes are configured such that at each step when secondaries are created, the main track is "paused," and the secondaries (the Cherenkov photons, for example) are immediately tracked to completion. Then tracking switches back to the electron, which takes another step, and so on.

  -- Michael Kelsey

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1 None: Re: Problem with TrackingAction::PostUserTrackingAction   (Mark Chernikov - 16 Oct, 2017)
(_ Idea: Re: Problem with TrackingAction::PostUserTrackingAction   (Michael H. Kelsey - 16 Oct, 2017)
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