RooBinnedGenContext.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 RooBinnedGenContext.cxx
\class RooBinnedGenContext
\ingroup Roofitcore

RooBinnedGenContext is an efficient implementation of the
generator context specific for binned pdfs
**/


#include "RooFit.h"

#include "Riostream.h"


#include "RooMsgService.h"
#include "RooBinnedGenContext.h"
#include "RooAbsPdf.h"
#include "RooRealVar.h"
#include "RooDataHist.h"
#include "RooDataSet.h"
#include "RooRandom.h"

using namespace std;

ClassImp(RooBinnedGenContext)
;
  

////////////////////////////////////////////////////////////////////////////////
/// Constructor

RooBinnedGenContext::RooBinnedGenContext(const RooAbsPdf &model, const RooArgSet &vars, 
               const RooDataSet *prototype, const RooArgSet* auxProto,
               Bool_t verbose) :
  RooAbsGenContext(model,vars,prototype,auxProto,verbose)
{
  cxcoutI(Generation) << "RooBinnedGenContext::ctor() setting up event special generator context for sum p.d.f. " << model.GetName() 
         << " for generation of observable(s) " << vars ;
  if (prototype) ccxcoutI(Generation) << " with prototype data for " << *prototype->get() ;
  if (auxProto && auxProto->getSize()>0)  ccxcoutI(Generation) << " with auxiliary prototypes " << *auxProto ;
  ccxcoutI(Generation) << endl ;

  // Constructor. Build an array of generator contexts for each product component PDF
  _pdfSet = (RooArgSet*) RooArgSet(model).snapshot(kTRUE) ;
  _pdf = (RooAbsPdf*) _pdfSet->find(model.GetName()) ;
  _pdf->setOperMode(RooAbsArg::ADirty,kTRUE) ;

  // Fix normalization set of this RooAddPdf
  if (prototype) 
    {
      RooArgSet coefNSet(vars) ;
      coefNSet.add(*prototype->get()) ;
      _pdf->fixAddCoefNormalization(coefNSet) ;
    }

  _pdf->recursiveRedirectServers(*_theEvent) ;
  _vars = _pdf->getObservables(vars) ;

  // If pdf has boundary definitions, follow those for the binning 
  RooFIter viter = _vars->fwdIterator() ;
  RooAbsArg* var ;
  while((var=viter.next())) {
    RooRealVar* rvar = dynamic_cast<RooRealVar*>(var) ;
    if (rvar) {
      list<Double_t>* binb = model.binBoundaries(*rvar,rvar->getMin(),rvar->getMax()) ;
      delete binb ;
    }
  }


  // Create empty RooDataHist
  _hist = new RooDataHist("genData","genData",*_vars) ;

  _expectedData = kFALSE ;
}


////////////////////////////////////////////////////////////////////////////////
/// Destructor. Delete all owned subgenerator contexts

RooBinnedGenContext::~RooBinnedGenContext()
{
  delete _vars ;
  delete _pdfSet ;
  delete _hist ;
}



////////////////////////////////////////////////////////////////////////////////
/// Attach given set of variables to internal p.d.f. clone

void RooBinnedGenContext::attach(const RooArgSet& args) 
{
  _pdf->recursiveRedirectServers(args) ;
}



////////////////////////////////////////////////////////////////////////////////
/// One-time initialization of generator contex. Attach theEvent
/// to internal p.d.f clone and forward initialization call to 
/// the component generators

void RooBinnedGenContext::initGenerator(const RooArgSet &theEvent)
{
  _pdf->recursiveRedirectServers(theEvent) ;

}


////////////////////////////////////////////////////////////////////////////////

void RooBinnedGenContext::setExpectedData(Bool_t flag) 
{
  _expectedData = flag ;
}


////////////////////////////////////////////////////////////////////////////////

RooDataSet *RooBinnedGenContext::generate(Double_t nEvt, Bool_t /*skipInit*/, Bool_t extended)
{
  // Scale to number of events and introduce Poisson fluctuations
  _hist->reset() ;

  Double_t nEvents = nEvt ;
  
  if (nEvents<=0) {
    if (!_pdf->canBeExtended()) {
      coutE(InputArguments) << "RooAbsPdf::generateBinned(" << GetName() 
             << ") ERROR: No event count provided and p.d.f does not provide expected number of events" << endl ;
      return 0 ;
    } else {
      // Don't round in expectedData mode
      if (_expectedData || extended) {
   nEvents = _pdf->expectedEvents(_vars) ;
      } else {
   nEvents = Int_t(_pdf->expectedEvents(_vars)+0.5) ;
      }
    }
  } 

  // Sample p.d.f. distribution
  _pdf->fillDataHist(_hist,_vars,1,kTRUE) ;  
  
  // Output container
  RooRealVar weight("weight","weight",0,1e9) ;
  RooArgSet tmp(*_vars) ;
  tmp.add(weight) ;
  RooDataSet* wudata = new RooDataSet("wu","wu",tmp,RooFit::WeightVar("weight")) ;

  vector<int> histOut(_hist->numEntries()) ;
  Double_t histMax(-1) ;
  Int_t histOutSum(0) ;
  for (int i=0 ; i<_hist->numEntries() ; i++) {
    _hist->get(i) ;
    if (_expectedData) { 

      // Expected data, multiply p.d.f by nEvents
      Double_t w=_hist->weight()*nEvents ;
      wudata->add(*_hist->get(),w) ;

    } else if (extended) {

      // Extended mode, set contents to Poisson(pdf*nEvents)
      Double_t w = RooRandom::randomGenerator()->Poisson(_hist->weight()*nEvents) ;
      wudata->add(*_hist->get(),w) ;
      
    } else {

      // Regular mode, fill array of weights with Poisson(pdf*nEvents), but to not fill
      // histogram yet.
      if (_hist->weight()>histMax) {
   histMax = _hist->weight() ;
      }
      histOut[i] = RooRandom::randomGenerator()->Poisson(_hist->weight()*nEvents) ;
      histOutSum += histOut[i] ;
    }
  }


  if (!_expectedData && !extended) {

    // Second pass for regular mode - Trim/Extend dataset to exact number of entries

    // Calculate difference between what is generated so far and what is requested
    Int_t nEvtExtra = abs(Int_t(nEvents)-histOutSum) ;
    Int_t wgt = (histOutSum>nEvents) ? -1 : 1 ;

    // Perform simple binned accept/reject procedure to get to exact event count
    while(nEvtExtra>0) {

      Int_t ibinRand = RooRandom::randomGenerator()->Integer(_hist->numEntries()) ;
      _hist->get(ibinRand) ;
      Double_t ranY = RooRandom::randomGenerator()->Uniform(histMax) ;

      if (ranY<_hist->weight()) {
   if (wgt==1) {
     histOut[ibinRand]++ ;
   } else {
     // If weight is negative, prior bin content must be at least 1
     if (histOut[ibinRand]>0) {
       histOut[ibinRand]-- ;
     } else {
       continue ;
     }
   }
   nEvtExtra-- ;
      }
    }

    // Transfer working array to histogram
    for (int i=0 ; i<_hist->numEntries() ; i++) {
      _hist->get(i) ;
      wudata->add(*_hist->get(),histOut[i]) ;      
    }    

  } 

  return wudata ;

}



////////////////////////////////////////////////////////////////////////////////
/// this method is not implemented for this context

void RooBinnedGenContext::generateEvent(RooArgSet&, Int_t)
{
  assert(0) ;
}



////////////////////////////////////////////////////////////////////////////////
/// Print the details of the context

void RooBinnedGenContext::printMultiline(ostream &os, Int_t content, Bool_t verbose, TString indent) const 
{
  RooAbsGenContext::printMultiline(os,content,verbose,indent) ;
  os << indent << "--- RooBinnedGenContext ---" << endl ;
  os << indent << "Using PDF ";
  _pdf->printStream(os,kName|kArgs|kClassName,kSingleLine,indent);
}