RooRecursiveFraction.cxx

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/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitCore                                                       *
 * @(#)root/roofitcore:$Id$
 * Authors:                                                                  *
 *   WV, Wouter Verkerke, UC Santa Barbara, verkerke@slac.stanford.edu       *
 *   DK, David Kirkby,    UC Irvine,         dkirkby@uci.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/
 
/**
\file RooRecursiveFraction.cxx
\class RooRecursiveFraction
\ingroup Roofitcore
 
A RooAbsReal implementation that
calculates the plain fraction of sum of RooAddPdf components
from a set of recursive fractions: for a given set of input fractions
\f$ {a_i} \f$, it returns \f$ a_n * \prod_{i=0}^{n-1} (1 - a_i) \f$.
**/
 
#include "Riostream.h"
#include <cmath>
 
#include "RooRecursiveFraction.h"
#include "RooAbsReal.h"
#include "RooAbsPdf.h"
#include "RooErrorHandler.h"
#include "RooArgSet.h"
#include "RooMsgService.h"
 
#include <RooFit/Detail/MathFuncs.h>
 
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor of plain RooAddPdf fraction from list of recursive fractions
 
RooRecursiveFraction::RooRecursiveFraction(const char* name, const char* title, const RooArgList& fracList) :
  RooAbsReal(name, title),
  _list("list","First set of components",this)
{
  for (Int_t ifrac=fracList.size()-1 ; ifrac>=0 ; ifrac--) {
    RooAbsArg* comp = fracList.at(ifrac) ;
    if (!dynamic_cast<RooAbsReal*>(comp)) {
      std::stringstream errorMsg;
      errorMsg << "RooRecursiveFraction::ctor(" << GetName() << ") ERROR: component " << comp->GetName()
             << " is not of type RooAbsReal" << std::endl;
      coutE(InputArguments) << errorMsg.str();
      throw std::invalid_argument(errorMsg.str());
    }
 
    _list.add(*comp) ;
  }
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Copy constructor
 
RooRecursiveFraction::RooRecursiveFraction(const RooRecursiveFraction& other, const char* name) :
  RooAbsReal(other, name),
  _list("list",this,other._list)
{
 
}
 
////////////////////////////////////////////////////////////////////////////////
/// Calculate and return value of \f$ a_n * \prod_{i=0}^{n-1} (1 - a_i) \f$.
double RooRecursiveFraction::evaluate() const
{
  const RooArgSet* nset = _list.nset() ;
 
  // Note that input coefficients are saved in reverse in this list.
  double prod = static_cast<RooAbsReal&>(_list[0]).getVal(nset);
 
  for (unsigned int i=1; i < _list.size(); ++i) {
    prod *= (1 - static_cast<RooAbsReal&>(_list[i]).getVal(nset));
  }
 
  return prod ;
}