[RF] RooTruthModel analytical integrals for general integration ranges

The analytical integral code of the `RooTruthModel` was making the wrong
assumption that if one uses the single-sided bases, the minimum x value
is always at zero (or the maximum value at zero, for the case of the
flipped bases).

This resulted in wrong integral values when integrating over a subrange,
as reported here on the forum:

https://root-forum.cern.ch/t/possible-bug-in-integration-of-roobdecay-and-rooabsanaconvpdf/56968

This commit rewrites the RooTruthModel analytical integral code to also
consider these cases. To avoid that with the additional code branches
the code becomes too verbose, the code was refactored to use a helper
function for evaluating indefinite integrals of symmetric or asymmetric
basis functions.

The refactored code is tested by the integration tests in `stressRooFit`,
and the problem that was reported on the forum is covered by a new unit
test.

roofit/roofitcore/inc/RooTruthModel.h

@@ -39,7 +39,6 @@ class RooTruthModel : public RooResolutionModel {
   RooTruthModel(const char *name, const char *title, RooAbsRealLValue& x) ;
   RooTruthModel(const RooTruthModel& other, const char* name=nullptr);
   TObject* clone(const char* newname) const override { return new RooTruthModel(*this,newname) ; }
-  ~RooTruthModel() override;
 
   Int_t basisCode(const char* name) const override ;
 

roofit/roofitcore/src/RooAbsAnaConvPdf.cxx

@@ -467,66 +467,57 @@ Int_t RooAbsAnaConvPdf::getAnalyticalIntegralWN(RooArgSet& allVars,
 /// Set \f$ x \f$ must be contained in \f$ v \f$ and set \f$ y \f$ must be contained in \f$ w \f$.
 ///
 
-double RooAbsAnaConvPdf::analyticalIntegralWN(Int_t code, const RooArgSet* normSet, const char* rangeName) const
+double RooAbsAnaConvPdf::analyticalIntegralWN(Int_t code, const RooArgSet *normSet, const char *rangeName) const
 {
-  // WVE needs adaptation to handle new rangeName feature
-
-  // Handle trivial passthrough scenario
-  if (code==0) return getVal(normSet) ;
-
-  // Unpack master code
-  RooArgSet *intCoefSet, *intConvSet, *normCoefSet, *normConvSet ;
-  _codeReg.retrieve(code-1,intCoefSet,intConvSet,normCoefSet,normConvSet) ;
-
-  Int_t index(0) ;
-  double answer(0) ;
-
-  if (normCoefSet==nullptr&&normConvSet==nullptr) {
-
-    // Integral over unnormalized function
-    double integral(0) ;
-    const TNamed *_rangeName = RooNameReg::ptr(rangeName);
-    for (auto convArg : _convSet) {
-      auto conv = static_cast<RooAbsPdf*>(convArg);
-      double coef = getCoefNorm(index++,intCoefSet,_rangeName) ;
-      //cout << "coefInt[" << index << "] = " << coef << " " ; intCoefSet->Print("1") ;
-      if (coef!=0) {
-   integral += coef* conv->getNormObj(nullptr,intConvSet,_rangeName)->getVal();
-   cxcoutD(Eval) << "RooAbsAnaConv::aiWN(" << GetName() << ") [" << index-1 << "] integral += " << conv->getNorm(intConvSet) << endl ;
+   // WVE needs adaptation to handle new rangeName feature
+
+   // Handle trivial passthrough scenario
+   if (code == 0)
+      return getVal(normSet);
+
+   // Unpack master code
+   RooArgSet *intCoefSet, *intConvSet, *normCoefSet, *normConvSet;
+   _codeReg.retrieve(code - 1, intCoefSet, intConvSet, normCoefSet, normConvSet);
+
+   Int_t index(0);
+
+   if (normCoefSet == nullptr && normConvSet == nullptr) {
+      // Integral over unnormalized function
+      double integral(0);
+      const TNamed *rangeNamePtr = RooNameReg::ptr(rangeName);
+      for (auto *conv : static_range_cast<RooAbsPdf *>(_convSet)) {
+         double coef = getCoefNorm(index++, intCoefSet, rangeNamePtr);
+         if (coef != 0) {
+            const double term = coef * conv->getNormObj(nullptr, intConvSet, rangeNamePtr)->getVal();
+            integral += term;
+            cxcoutD(Eval) << "RooAbsAnaConv::aiWN(" << GetName() << ") [" << index - 1 << "] integral += " << term
+                          << std::endl;
+         }
       }
+      return integral;
+   }
 
-    }
-    answer = integral ;
-
-  } else {
-
-    // Integral over normalized function
-    double integral(0) ;
-    double norm(0) ;
-    const TNamed *_rangeName = RooNameReg::ptr(rangeName);
-    for (auto convArg : _convSet) {
-      auto conv = static_cast<RooAbsPdf*>(convArg);
-
-      double coefInt = getCoefNorm(index,intCoefSet,_rangeName) ;
-      //cout << "coefInt[" << index << "] = " << coefInt << "*" << term << " " << (intCoefSet?*intCoefSet:RooArgSet()) << endl ;
-      if (coefInt!=0) {
-   double term = conv->getNormObj(nullptr,intConvSet,_rangeName)->getVal();
-   integral += coefInt*term ;
-      }
+   // Integral over normalized function
+   double integral(0);
+   double norm(0);
+   const TNamed *rangeNamePtr = RooNameReg::ptr(rangeName);
+   for (auto *conv : static_range_cast<RooAbsPdf *>(_convSet)) {
 
-      double coefNorm = getCoefNorm(index,normCoefSet) ;
-      //cout << "coefNorm[" << index << "] = " << coefNorm << "*" << term << " " << (normCoefSet?*normCoefSet:RooArgSet()) << endl ;
-      if (coefNorm!=0) {
-   double term = conv->getNormObj(nullptr,normConvSet)->getVal();
-   norm += coefNorm*term ;
+      double coefInt = getCoefNorm(index, intCoefSet, rangeNamePtr);
+      if (coefInt != 0) {
+         double term = conv->getNormObj(nullptr, intConvSet, rangeNamePtr)->getVal();
+         integral += coefInt * term;
       }
 
-      index++ ;
-    }
-    answer = integral/norm ;
-  }
+      double coefNorm = getCoefNorm(index, normCoefSet);
+      if (coefNorm != 0) {
+         double term = conv->getNormObj(nullptr, normConvSet)->getVal();
+         norm += coefNorm * term;
+      }
 
-  return answer ;
+      index++;
+   }
+   return integral / norm;
 }