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Re: Fitting scheme [message #1988 is a reply to message #1987] Wed, 12 May 2010 10:03 Go to previous messageGo to previous message
Messages: 78
Registered: March 2006
Location: University of Victoria
rosemann wrote on Wed, 12 May 2010 04:52

Hi Jason,

So my proposal would be to call the two functions in the TrackFitterBase, including a third one (which is optional, but might be more interesting down the line)
  • calculateDistances(...)
  • calculateResiduals(...)
  • calculateResolution(...)

In fact, it is even more complicated than that. The "residuals" from the likelihood method are in units of charge or electrons.


I think it is not a good idea to let the processor handle the logic, for several reasons. The extra overhead needed for the determination of the fit method is not large, but somehow confusing. As you mention, several things would get mixed by doing it this way.

I agree, this is what led me to the idea of having pairs of fitting processors: one for fitting and one for doing the analysis.


The underlying problem is of course something else -- the LCIO objects lack some, eventually fundamental functionality. For example, if it was possible to attach a hit to track, but mark it "unused", then we would have the solution. This would encode all information from the fitting inside the data object. It would also go beyond the scope of fitting.

There is an LCRelation from LCIO. I believe these are used to abstractly associate two LCIO objects with a single weighting parameter.

Do you mean marking a track as unused for the purpose of calculating the "distance" measure that was previously defined?

If that is the case then this would be a good motivator for using the dual-class approach. The algorithm for calculation these distances could be contained in a "TrackResidualChiSquaredProcessor".


a) what do you mean by "reconstruction method" ?

The type of fitter used. So, is it likely that multiple types of track fitters will be used to reconstruct/analyse the data during one execution of Marlin processor chain?
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