AliTrackResidualsChi2.cxx

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 * Author: The ALICE Off-line Project.                                    *
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//-----------------------------------------------------------------
//   Implementation of the derived class for track residuals
//   based on Chi2 minimization
//
//-----------------------------------------------------------------

#include <TVirtualFitter.h>
#include <TGeoMatrix.h>

#include "AliAlignObj.h"
#include "AliTrackPointArray.h"
#include "AliTrackResidualsChi2.h"



void TrackResidualsChi2Fcn(Int_t &npar, Double_t *gin, Double_t &f, Double_t *x, Int_t iflag);


ClassImp(AliTrackResidualsChi2)


//______________________________________________________________________________
void TrackResidualsChi2Fcn(Int_t &npar, Double_t *gin, Double_t &f, Double_t *par, Int_t iflag)
{
  // This function is called by minuit
  // The corresponding member method is called
  // using SetObjectFit/GetObjectFit methods of TMinuit
  AliTrackResidualsChi2* dummy = (AliTrackResidualsChi2 *)TVirtualFitter::GetFitter()->GetObjectFit();
  dummy->Chi2(npar, gin, f, par, iflag);
}

//______________________________________________________________________________
Bool_t AliTrackResidualsChi2::Minimize()
{
  // Implementation of Chi2 based minimization
  // of track residuala sum
  // 
  // CHOLM: Modified to use the TVirtualFitter interface only.  This
  // makes it possible other fitters than TMinuit (say TMinuit2,
  // TFumili) by simply changing ones configuration file, or setting
  // it up in a script.  Much more robust and flexible. 
  Double_t arglist[10];
  Int_t ierflg = 0;
  TVirtualFitter *fitter = TVirtualFitter::Fitter(this,6);  //initialize TMinuit
  arglist[0] = -1;
  ierflg = fitter->ExecuteCommand("SET PRINT", arglist, 1);

  fitter->SetFCN(TrackResidualsChi2Fcn);

  arglist[0] = 1;
  ierflg = fitter->ExecuteCommand("SET ERR", arglist ,1);

  // Set starting values and step sizes for parameters
  Double_t pars[6] = {0,0,0,0,0,0};
  for(Int_t i=0;i<6;i++) if(fBFixed[i]) pars[i]=fFixed[i];
  Double_t step[6] = {0.0001,0.0001,0.0001,0.0001,0.0001,0.0001};
  ierflg = fitter->SetParameter(0, "dx", pars[0], step[0], 0,0);
  ierflg = fitter->SetParameter(1, "dy", pars[1], step[1], 0,0);
  ierflg = fitter->SetParameter(2, "dz", pars[2], step[2], 0,0);
  ierflg = fitter->SetParameter(3, "psi", pars[3], step[3], 0,0);
  ierflg = fitter->SetParameter(4, "theta", pars[4], step[4], 0,0);
  ierflg = fitter->SetParameter(5, "phi", pars[5], step[5], 0,0);

  // Fix parameters
  if(fBFixed[0]) {printf("Fixing dx=%f\n",pars[0]); fitter->FixParameter(0);}
  if(fBFixed[1]) {printf("Fixing dy=%f\n",pars[1]); fitter->FixParameter(1);}
  if(fBFixed[2]) {printf("Fixing dz=%f\n",pars[2]); fitter->FixParameter(2);}
  if(fBFixed[3]) {printf("Fixing psi=%f\n",pars[3]); fitter->FixParameter(3);}
  if(fBFixed[4]) {printf("Fixing theta=%f\n",pars[4]); fitter->FixParameter(4);}
  if(fBFixed[5]) {printf("Fixing phi=%f\n",pars[5]); fitter->FixParameter(5);}

  // Now ready for minimization step
  arglist[0] = 500;
  arglist[1] = 1.;
  fitter->ExecuteCommand("MIGRAD", arglist ,2);

  // Print results
  Double_t amin,edm,errdef;
  Int_t nvpar,nparx,icstat;
  icstat = fitter->GetStats(amin,edm,errdef,nvpar,nparx);

   //Construct the covariance matrix for AlignObj
  Double_t *cov=fitter->GetCovarianceMatrix(); 
  Int_t unfixedparam=6;
  Int_t fixedparamat[6]={0,0,0,0,0,0};
  if(fBFixed[0]==kTRUE){
    unfixedparam--;
    fixedparamat[0]=1;
  }
  for(Int_t j=1;j<6;j++){
    if(fBFixed[j]==kTRUE){
      unfixedparam--;
      fixedparamat[j]=fixedparamat[j-1]+1;
    }
    else fixedparamat[j]=fixedparamat[j-1];
  }
  
  Double_t cov2[36];
  for(Int_t i=0;i<6;i++){
    for(Int_t j=0;j<6;j++){
      if(fBFixed[i]==kTRUE||fBFixed[j]==kTRUE){
        cov2[i+6*j]=0.;
      }
      else cov2[i+6*j]=cov[i-fixedparamat[i]+6*(j-fixedparamat[j])];
    
    }
  }
  
  Double_t covmatrarray[21];
  for(Int_t j=0;j<6;j++){
    for(Int_t i=j;i<6;i++){
      covmatrarray[i*(i+1)/2+j]=cov2[i+6*j];
    }
  }
  
  //  printf("covar 2:  %.10f  \n   %.10f ; %.10f ;  \n; %.10f;  %.10f;  %.10f; \n  %.10f; %.10f;  %.10f;  %.10f;  \n  %.10f ; %.10f  ;  %.10f  ;  %.10f  ;  %.10f \n %.10f ;  %.10f ;  %.10f  ;  %.10f  ;  %.10f  ;  %.10f   ;\n",covmatrarray[0],covmatrarray[1],covmatrarray[2],covmatrarray[3],covmatrarray[4],covmatrarray[5],covmatrarray[6],covmatrarray[7],covmatrarray[8],covmatrarray[9],covmatrarray[10],covmatrarray[11],covmatrarray[12],covmatrarray[13],covmatrarray[14],covmatrarray[15],covmatrarray[16],covmatrarray[17],covmatrarray[18],covmatrarray[19],covmatrarray[20]);
  
  
  fAlignObj->SetCorrMatrix(covmatrarray);
  fChi2 = amin; fNdf -= nvpar;
  
  return kTRUE;
}

//______________________________________________________________________________
void AliTrackResidualsChi2::Chi2(Int_t & /* npar */, Double_t * /* gin */, Double_t &f, Double_t *par, Int_t /* iflag */)
{
  // Chi2 function to be minimized
  // Sums all the track residuals
  Double_t chi2 = 0;

  fAlignObj->SetPars(par[0],par[1],par[2],par[3],par[4],par[5]);

  AliTrackPoint p1,p2;

  Bool_t count = kFALSE;
  if (fNdf == 0) count = kTRUE;

  for (Int_t itrack = 0; itrack < fLast; itrack++) {
    if (!fVolArray[itrack] || !fTrackArray[itrack]) continue;
    for (Int_t ipoint = 0; ipoint < fVolArray[itrack]->GetNPoints(); ipoint++) {
      fVolArray[itrack]->GetPoint(p1,ipoint);
      fAlignObj->Transform(p1);
      fTrackArray[itrack]->GetPoint(p2,ipoint);
      Float_t residual = p2.GetResidual(p1,kTRUE);
      chi2 += residual;
      if (count) fNdf += 3;
    }
  }
  f = chi2;
}