// This program can be execute from the command line as folows:
//
// root -l foam_kanwa.C
//_____________________________________________________________________________
Int_t foam_kanwa(){
cout<<"--- kanwa started ---"<<endl;
gSystem->Load("libFoam.so");
TH2D *hst_xy = new TH2D("hst_xy" , "x-y plot", 50,0,1.0, 50,0,1.0);
Double_t *MCvect =new Double_t[2]; // 2-dim vector generated in the MC run
//
TRandom *PseRan = new TRandom3(); // Create random number generator
PseRan->SetSeed(4357);
TFoam *FoamX = new TFoam("FoamX"); // Create Simulator
FoamX->SetkDim(2); // No. of dimensions, obligatory!
FoamX->SetnCells(500); // Optionally No. of cells, default=2000
FoamX->SetRhoInt(Camel2); // Set 2-dim distribution, included below
FoamX->SetPseRan(PseRan); // Set random number generator
FoamX->Initialize(); // Initialize simulator, may take time...
//
// visualising generated distribution
TCanvas *cKanwa = new TCanvas("cKanwa","Canvas for plotting",600,600);
cKanwa->cd();
// From now on FoamX is ready to generate events
int nshow=5000;
for(long loop=0; loop<100000; loop++){
FoamX->MakeEvent(); // generate MC event
FoamX->GetMCvect( MCvect); // get generated vector (x,y)
Double_t x=MCvect[0];
Double_t y=MCvect[1];
if(loop<10) cout<<"(x,y) = ( "<< x <<", "<< y <<" )"<<endl;
hst_xy->Fill(x,y);
// live plot
if(loop == nshow){
nshow += 5000;
hst_xy->Draw("lego2");
cKanwa->Update();
}
}// loop
//
hst_xy->Draw("lego2"); // final plot
cKanwa->Update();
//
Double_t MCresult, MCerror;
FoamX->GetIntegMC( MCresult, MCerror); // get MC integral, should be one
cout << " MCresult= " << MCresult << " +- " << MCerror <<endl;
cout<<"--- kanwa ended ---"<<endl;
return 0;
}//kanwa
//_____________________________________________________________________________
Double_t sqr(Double_t x){return x*x;};
//_____________________________________________________________________________
Double_t Camel2(Int_t nDim, Double_t *Xarg){
// 2-dimensional distribution for Foam, normalized to one (within 1e-5)
Double_t x=Xarg[0];
Double_t y=Xarg[1];
Double_t GamSq= sqr(0.100e0);
Double_t Dist= 0;
Dist +=exp(-(sqr(x-1./3) +sqr(y-1./3))/GamSq)/GamSq/TMath::Pi();
Dist +=exp(-(sqr(x-2./3) +sqr(y-2./3))/GamSq)/GamSq/TMath::Pi();
return 0.5*Dist;
}// Camel2
//_____________________________________________________________________________