Dear Roofit experts,
I’ve embedded a C++ function into my Roofit project creating a class that extends the RooAbsPdf.
The function is a black box with a method evaluatePDF(&pdf_val, &pdf_norm, observables…, parameters…).
Once called the pdf_val and pdf_nor are initialized with the result of the evaluation.
I’ve implemented the evaluate as follow:
Double_t MyPDF::evaluate() const {
double pdf_val;
double pdf_norm;
evaluatePDF(&pdf_norm, &pdf_val,x,a,b,c,high,low,e….);
return pdf_val;
}
high and low are the boundaries of the observable x.
and the getAnalyticalIntegral and analyticalIntegral as follow:
Int_t MyPDF::getAnalyticalIntegral(RooArgSet &allVars, RooArgSet &analVars, const char rangeName) const{
if(matchArgs(allVars, analVars, x)) return 1;
return 0;
}
Double_t MyPDF::analyticalIntegral(Int_t code, const char *rangeName) const{
if(code !=0) {
double pdf_norm;
double pdf_val;
evaluatePDF(&pdf_norm, &pdf_val,x,a,b,c,high,low,e….);
return pdf_norm;
}
return 0;
}
I’m finding several issues in normalization as plots are completely wrong, especially when using it inside a RooSimultaneous.
My concern is that I’m doing some mistakes in this analyticalIntegral implementation.
I did several checks and trials in order to find exactly the issue. In one of these checks I printed the integral of the simultaneous in the x variable in this way:
self.model = ROOT.RooSimultaneous(
”simultaneous”,
”simultaneous”,
mix_unmix_cat)
self.model.addPdf(mypdf1, MIX)
self.model.addPdf(mypdf2, UNMIX)
mix_unmix_cat.setLabel(MIX)
igx = self.model.createIntegral(RooArgSet(x))
print(”MIX gx_Int[dt] = %f”% (igx.getVal()))
mix_unmix_cat.setLabel(UNMIX)
igx = self.model.createIntegral(RooArgSet(x))
print(”UNMIX gx_Int[dt] = %f”% (igx.getVal()))
I printed first igx.getVal() when using the analyticalIntegral. The result was
not correct because I found :
UNMIXED gx_Int[dt] = 1.0000
MIX gx_Int[dt] = 1.0000
Then I forced the getAnalyticalIntegral to return always 0 in order to use the numerical integration and I got the correct result.
UNMIXED gx_Int[dt] = 0.816937
MIX gx_Int[dt] = 0.183063
Can you suggest me how to correctly implement the normalization when using the simultaneous pdf?
I think there are no issues without simultaneous in the normalization.
