using SetFCN

Dear all

I have difficulties whit changing fitting function. There is a need to fit a histogram event-by-event with "I" integral option but it is very slow. To make it faster I decided to reduce the precision of integral calculation. For that I just copy TFitter::FitChisquareI function, modify few lines in oreder to be able to compile it ( get pointer to fitter, and replace direct use of data members with fitter->fDataMember, see the attachment). May be there is a better way to reduce the precision of integral calculation, but at least I don't know it.

First I would like to be sure that it works with default 1e-12 precision and in my code I call

(TVirtualFitter::Fitter(h))->SetFCN(MyH1FitChisquareIntegral); h->Fit(f, "U");

but the fit fails, while if I don't call SetFCN and do h->Fit(f, "I") it works. Am I missing something ?

Thanks a lot,
Margar

P.S I am using ROOT 5.14 on SLC3 with gcc 3.2.3