//----------------------------------------------------------------
//
// File  : fit_problem.C
// Date  : 20060717
// Author: Jeroen Hegeman
//         (jhegeman@fnal.gov)
//
// How-to: root [0] .L fit_problem.C+
//         root [1] ShowProblem()
//
//----------------------------------------------------------------

#include <iostream>
#include "TH1F.h"
#include "TRandom.h"
#include "TVirtualFitter.h"

void MyFCN(Int_t& npar, Double_t* gin, Double_t& f, Double_t* par, Int_t flag);

void ShowProblem()
{
  TNamed dummy("dummy","dummy");

  TH1F* histo = new TH1F("histo","Gaussian",100,-8,8);

  gRandom->SetSeed();

  Float_t rnd;
  for (Int_t i = 0; i < 10000; ++i) {
    rnd = gRandom->Gaus(3,0.5);
    histo->Fill(rnd);
  } // for (i)

  TVirtualFitter* fitter = TVirtualFitter::Fitter(histo);
  fitter->Clear();

  fitter->SetFCN(MyFCN);
  fitter->SetObjectFit(&dummy);

  //================================================================
  TObject* fitObject = TVirtualFitter::GetFitter()->GetObjectFit();
  std::cout << "============================" << endl;
  std::cout << "ShowProblem fitObject            = '"
	    << fitObject << "'" << std::endl;
  if (fitObject)
    std::cout << "ShowProblem fitObject->GetName() = '"
	      << fitObject->GetName() << "'" << std::endl;
  std::cout << "============================" << endl;
  //================================================================

  histo->Fit("gaus","U");

  delete histo;
  histo = 0;

} // ShowProblem

//----------------------------------------------------------------

void MyFCN(Int_t& npar, Double_t* gin, Double_t& f, Double_t* par, Int_t flag)
{
  // Just to avoid a lot of the same messages...
  static size_t count = 0;

  if (count == 0) {
    //================================================================
    TObject* fitObject = TVirtualFitter::GetFitter()->GetObjectFit();
    std::cout << "============================" << endl;
    std::cout << "MyFCN fitObject            = '"
	      << fitObject << "'" << std::endl;
    if (fitObject)
      std::cout << "MyFCN fitObject->GetName() = '"
		<< fitObject->GetName() << "'" << std::endl;
    std::cout << "============================" << endl;
    //================================================================
  } // if (count)

  ++count;
  return;
} // MyFCN

//----------------------------------------------------------------