RootFitter does not do anything useful and needs updated

[spaulaus]

Description

The RootFitter class doesn't do anything useful. Development was stalled out on it since there was some kind of funky ROOT related compilation issue. This issue has since been resolved and this fitter should be fixed. Implementation of this fitter along with the additional Function classes provides programs that do fitting (utkscan, scope) a consistent functional framework to work from.

Work to be completed

• Update RootFitter so that it produces viable results
• Update unittest-RootFitter so that it tests all of the failure modes that the RootFitter can return.
• Update FittingAnalyzer so that it has an option for using the RootFitter class.
• Update FittingAnalyzer so that it still compiles if ROOT is not found in the system.
• Scope uses the VandleTimingFunction for fitting.

Acceptance Criteria

• Successful compilation if ROOT is not found in the system but GSL is found.
• RootFitter class passes all of the unittests.
• RootFitter analysis results are not statistically different than results from GslFitter.

[spaulaus]

Test data information

I analyzed kqxhc:/data/utk/pixieworkshop/pulser_003.ldf. The configuration file can be found here. I made minor modifications to the configuration file to reflect some updates to the software.

Results using GslFitter (reference histogram)

The FWHM of the Time Difference was 33.7208 ps

Results using RootFitter

The FWHM of the Time Difference was 33.7244 ps

Processing times

The scan spends on average (20 samples) 52% more time in the FittingAnalyzer when we are using the RootFitter than the GslFitter. This result isn't surprising. The GslFitter uses predefined functions and derivatives to perform the fit, where as ROOT uses numerical methods to calculate the derivatives. Another reason is that we are setting up a TGraph before each fit. The overhead of creating the TGraph at each iteration may be causing some speed issues as well.

Conclusions

The RootFitter will work for analyzing signals. It only supports the VandleTimingFunction.