%%cpp -d
#include "TH1.h"
#include "TF1.h"
#include "TH2D.h"
#include "TF2.h"
#include "TCanvas.h"
#include "TStopwatch.h"
#include "TSystem.h"
#include "TRandom3.h"
#include "TVirtualFitter.h"
#include "TPaveLabel.h"
#include "TStyle.h"


TF2 *fitFcn;
TH2D *histo;

%%cpp -d
double gaus2D(double *x, double *par) {
   double t1 =   x[0] - par[1];
   double t2 =   x[1] - par[2];
   return par[0]* exp( - 0.5 * (  t1*t1/( par[3]*par[3]) + t2*t2  /( par[4]*par[4] )  ) ) ;
}

%%cpp -d
double fitFunction(double *x, double *par) {
  return gaus2D(x,par);
}

%%cpp -d
void fillHisto(int n =10000) {

  gRandom = new TRandom3();
  for (int i = 0; i < n; ++i) {
     double x = gRandom->Gaus(2,3);
     double y = gRandom->Gaus(-1,4);
     histo->Fill(x,y,1.);
  }
}

%%cpp -d
void DoFit(const char* fitter, TVirtualPad *pad, int npass) {
   TStopwatch timer;
   TVirtualFitter::SetDefaultFitter(fitter);
   pad->SetGrid();
   fitFcn->SetParameters(100,0,0,2,7);
   fitFcn->Update();

   timer.Start();
   histo->Fit("fitFcn","0");
   timer.Stop();

   histo->Draw();
   double cputime = timer.CpuTime();
   printf("%s, npass=%d  : RT=%7.3f s, Cpu=%7.3f s\n",fitter,npass,timer.RealTime(),cputime);
   TPaveLabel *p = new TPaveLabel(0.5,0.7,0.85,0.8,Form("%s CPU= %g s",fitter,cputime),"brNDC");
   p->Draw();
   pad->Update();
}

int n = 100000;

TH1::AddDirectory(false);
TCanvas *c1 = new TCanvas("c1","Fitting Demo",10,10,900,900);
c1->Divide(2,2);

fitFcn = new TF2("fitFcn",fitFunction,-10,10,-10,10,5);

gStyle->SetOptFit();
gStyle->SetStatY(0.6);


histo = new TH2D("h2","2D Gauss",100,-10,10,100,-10,10);
fillHisto(n);

int npass=0;

c1->cd(1);
DoFit("Minuit",gPad,npass);

c1->cd(2);
  DoFit("Fumili",gPad,npass);

c1->cd(3);
DoFit("Minuit2",gPad,npass);

c1->cd(4);
DoFit("Fumili2",gPad,npass);

%jsroot on
gROOT->GetListOfCanvases()->Draw()