Virtual Fitter question

Dear Rooters,

I am trying to find the best way to fit MC toy data. For this I created a small script (tamuMCtoy_0.cxx) where I generate the data according to some function and thereafter using the same function trying to fit toy data with various virtual fitters available in the ROOT. Using just default fitter MINUIT (as well as for FUMILI fitter) everything works OK, however when I
switched to MINUIT2 or FUMILI2 the fit is not working at all. Maybe I have
to modify the fitting function that it would be more appropriate to mentioned fitters. I would be appreciated for any help or suggestions.

In addition I am also curious why the value of the FCN (chi2) function in
the listing of fit (out.txt) is different from the explicit call of value for chi2?

FCN=5414.97 FROM MINOS STATUS=SUCCESSFUL vs —> chi2: 520.98264


6 August 2007
out.txt (4.31 KB)
tamuMCtoy_0.cxx (4.99 KB)

Lorenzo will investigate this problem with Minuit2 once he will be back from holidays.


Thank you Victor for reporting this.

There was a bug in the Minuit2 implementation of the TVirtualFitter and it should be fixed now in CVS,

Best Regards