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   "source": [
    "# foam_kanwa\n",
    "This program can be execute from the command line as folows:\n",
    "\n",
    "```cpp\n",
    "     root -l foam_kanwa.C\n",
    "```\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Stascek Jadach  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:25 PM.</small></i>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "ab1c4799",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%%cpp -d\n",
    "#include \"Riostream.h\"\n",
    "#include \"TFoam.h\"\n",
    "#include \"TCanvas.h\"\n",
    "#include \"TH2.h\"\n",
    "#include \"TMath.h\"\n",
    "#include \"TFoamIntegrand.h\"\n",
    "#include \"TRandom3.h\""
   ]
  },
  {
   "cell_type": "markdown",
   "id": "687d496e",
   "metadata": {},
   "source": [
    " _____________________________________________________________________________\n",
    " "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9e9f5d41",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%%cpp -d\n",
    "Double_t sqr(Double_t x){\n",
    "   return x*x;\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "40a39133",
   "metadata": {},
   "source": [
    " _____________________________________________________________________________\n",
    " "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "0edf3855",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%%cpp -d\n",
    "Double_t Camel2(Int_t nDim, Double_t *Xarg){\n",
    "   // 2-dimensional distribution for Foam, normalized to one (within 1e-5)\n",
    "   Double_t x=Xarg[0];\n",
    "   Double_t y=Xarg[1];\n",
    "   Double_t GamSq= sqr(0.100e0);\n",
    "   Double_t Dist= 0;\n",
    "   Dist +=exp(-(sqr(x-1./3) +sqr(y-1./3))/GamSq)/GamSq/TMath::Pi();\n",
    "   Dist +=exp(-(sqr(x-2./3) +sqr(y-2./3))/GamSq)/GamSq/TMath::Pi();\n",
    "   return 0.5*Dist;\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9392155b",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "cout<<\"--- kanwa started ---\"<<endl;\n",
    "TH2D  *hst_xy = new TH2D(\"hst_xy\" ,  \"x-y plot\", 50,0,1.0, 50,0,1.0);\n",
    "Double_t MCvect[2]; // 2-dim vector generated in the MC run"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3dcd539e",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TRandom     *PseRan   = new TRandom3();  // Create random number generator\n",
    "PseRan->SetSeed(4357);\n",
    "TFoam   *FoamX    = new TFoam(\"FoamX\");   // Create Simulator\n",
    "FoamX->SetkDim(2);         // No. of dimensions, obligatory!\n",
    "FoamX->SetnCells(500);     // Optionally No. of cells, default=2000\n",
    "FoamX->SetRhoInt(Camel2);  // Set 2-dim distribution, included below\n",
    "FoamX->SetPseRan(PseRan);  // Set random number generator\n",
    "FoamX->Initialize();       // Initialize simulator, may take time..."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "42795fdc",
   "metadata": {},
   "source": [
    "visualising generated distribution"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6acdf28e",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TCanvas *cKanwa = new TCanvas(\"cKanwa\",\"Canvas for plotting\",600,600);\n",
    "cKanwa->cd();"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8b4cfb7e",
   "metadata": {},
   "source": [
    "From now on FoamX is ready to generate events"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f3a78ec6",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "int nshow=5000;\n",
    "for(long loop=0; loop<100000; loop++){\n",
    "   FoamX->MakeEvent();            // generate MC event\n",
    "   FoamX->GetMCvect( MCvect);     // get generated vector (x,y)\n",
    "   Double_t x=MCvect[0];\n",
    "   Double_t y=MCvect[1];\n",
    "   if(loop<10) cout<<\"(x,y) =  ( \"<< x <<\", \"<< y <<\" )\"<<endl;\n",
    "   hst_xy->Fill(x,y);\n",
    "   // live plot\n",
    "   if(loop == nshow){\n",
    "      nshow += 5000;\n",
    "      hst_xy->Draw(\"lego2\");\n",
    "      cKanwa->Update();\n",
    "   }\n",
    "}// loop"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7ebcea38",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "hst_xy->Draw(\"lego2\");  // final plot\n",
    "cKanwa->Update();"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "05a38b47",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "Double_t MCresult, MCerror;\n",
    "FoamX->GetIntegMC( MCresult, MCerror);  // get MC integral, should be one\n",
    "cout << \" MCresult= \" << MCresult << \" +- \" << MCerror <<endl;\n",
    "cout<<\"--- kanwa ended ---\"<<endl;\n",
    "\n",
    "return 0;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "26931cc9",
   "metadata": {},
   "source": [
    "Draw all canvases "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "351aa7e0",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%jsroot on\n",
    "gROOT->GetListOfCanvases()->Draw()"
   ]
  }
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