[u/mrichter/AliRoot.git] / ITS / AliITSsimulationSPD.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

#include <Riostream.h>
#include <TRandom.h>
#include <TH1.h>
#include <TMath.h>
#include <TString.h>
#include <TParticle.h>

#include "AliRun.h"
#include "AliITS.h"
#include "AliITShit.h"
#include "AliITSdigitSPD.h"
#include "AliITSmodule.h"
#include "AliITSMapA2.h"
#include "AliITSpList.h"
#include "AliITSsimulationSPD.h"
#include "AliITSsegmentation.h"
#include "AliITSresponse.h"
#include "AliITSsegmentationSPD.h"
#include "AliITSresponseSPD.h"

//#define DEBUG

ClassImp(AliITSsimulationSPD)
////////////////////////////////////////////////////////////////////////
// Version: 0
// Written by Rocco Caliandro
// from a model developed with T. Virgili and R.A. Fini
// June 15 2000
//
// AliITSsimulationSPD is the simulation of SPDs
//
//______________________________________________________________________
AliITSsimulationSPD::AliITSsimulationSPD() : AliITSsimulation(),
fMapA2(0),
fHis(0){
    // Default constructor
    // Inputs: 
    //    none.
    // Outputs:
    //    none.
    // Return:
    //    A default constructed AliITSsimulationSPD class.
}
//______________________________________________________________________
AliITSsimulationSPD::AliITSsimulationSPD(AliITSsegmentation *seg,
                                         AliITSresponse *res):
AliITSsimulation(seg,res),
fMapA2(0),
fHis(0){
    // Standard constructor
    // Inputs: 
    //    AliITSsegmentation *seg  Segmentation class to be used
    //    AliITSresonse      *res  Response class to be used
    // Outputs:
    //    none.
    // Return:
    //    A standard constructed AliITSsimulationSPD class.

    Init();
}
//______________________________________________________________________
void AliITSsimulationSPD::Init() {
    // Initilizes the variables of AliITSsimulation SPD.
    // Inputs:
    //    none.
    // Outputs:
    //    none.
    // Return:
    //    none.

    fHis = 0;
    if(fMapA2) delete fMapA2;
    fMapA2  = new AliITSMapA2(fSegmentation);
    if(fpList) delete fpList;
    fpList  = new AliITSpList(GetNPixelsZ()+1,GetNPixelsX()+1);
}
//______________________________________________________________________
void AliITSsimulationSPD::Init(AliITSsegmentationSPD *seg,
                               AliITSresponseSPD *resp) {
    // Initilizes the variables of AliITSsimulation SPD.
    // Inputs:
    //    AliITSsegmentationSPD   replacement segmentation class to be used
    //    aliITSresponseSPD       replacement response class to be used
    // Outputs:
    //    none.
    // Return:
    //    none.

    if(fHis){
        fHis->Delete(); 
        delete fHis;  
    } // end if fHis
    fHis = 0;
    if(fResponse) delete fResponse;
    fResponse     = resp;
    if(fSegmentation) delete fSegmentation;
    fSegmentation = seg;
    if(fMapA2) delete fMapA2;
    fMapA2  = new AliITSMapA2(fSegmentation);
    if(fpList) delete fpList;
    fpList  = new AliITSpList(GetNPixelsZ()+1,GetNPixelsX()+1);
}
//______________________________________________________________________
AliITSsimulationSPD::~AliITSsimulationSPD() { 
    // destructor
    // Inputs: 
    //    none.
    // Outputs:
    //    none.
    // Return:
    //    none.

    if(fMapA2) delete fMapA2;

    if (fHis) {
        fHis->Delete(); 
        delete fHis;     
    } // end if
}
//______________________________________________________________________
AliITSsimulationSPD::AliITSsimulationSPD(const AliITSsimulationSPD &source) :
    AliITSsimulation(source){
    // Copy Constructor
    // Inputs: 
    //    none.
    // Outputs:
    //    none.
    // Return:
    //    A new AliITSsimulationSPD class with the same parameters as source.

    if(&source == this) return;

    this->fMapA2    = source.fMapA2;
    this->fHis      = source.fHis;
    return;
}
//______________________________________________________________________
AliITSsimulationSPD& AliITSsimulationSPD::operator=(const AliITSsimulationSPD 
						    &source) {
    //    Assignment operator
    // Inputs: 
    //    none.
    // Outputs:
    //    none.
    // Return:
    //    A new AliITSsimulationSPD class with the same parameters as source.

    if(&source == this) return *this;

    this->fMapA2    = source.fMapA2;
    this->fHis      = source.fHis;
    return *this;
} 
//______________________________________________________________________
void AliITSsimulationSPD::InitSimulationModule(Int_t module,Int_t event){
    // Creates maps to build the list of tracks for each sumable digit
    // Inputs:
    //   Int_t module    // Module number to be simulated
    //   Int_t event     // Event number to be simulated
    // Outputs:
    //   none.
    // Return
    //    none.
 
    fModule = module;
    fEvent  = event;
    fMapA2->ClearMap();
    fpList->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSPD::FinishSDigitiseModule(){
    // Does the Sdigits to Digits work
    // Inputs:
    //   none.
    // Outputs:
    //   none.
    // Return:
    //   none.

    SDigitsToDigits(fModule,fpList);
}
//______________________________________________________________________
void AliITSsimulationSPD::SDigitiseModule(AliITSmodule *mod, Int_t dummy0,
                                             Int_t dummy1) {
    // Sum digitize module
    // Inputs:
    //   AliITSmodule  *mod    The module to be SDgitized
    //   Int_t         dummy0  Not used kept for general compatibility
    //   Int_t         dummy1  Not used kept for general compatibility
    // Outputs:
    //   none.
    // Return:
    //   none.
    if (!(mod->GetNhits())) return; // if module has no hits then no Sdigits.
    Int_t    number     = 10000;
    Int_t    *frowpixel = new Int_t[number];
    Int_t    *fcolpixel = new Int_t[number];
    Double_t *fenepixel = new Double_t[number];

    dummy0 = dummy1; // remove unsued variable warning.
    fModule = mod->GetIndex();

    // Array of pointers to store the track index of the digits
    // leave +1, otherwise pList crashes when col=256, row=192

    HitsToAnalogDigits(mod,frowpixel,fcolpixel,fenepixel,fpList);

    WriteSDigits(fpList);

    // clean memory
    delete[] frowpixel;
    delete[] fcolpixel;
    delete[] fenepixel;
    fMapA2->ClearMap();
    fpList->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSPD::DigitiseModule(AliITSmodule *mod, Int_t,Int_t) {
    // digitize module. Also need to digitize modules with only noise.
    // Inputs:
    //   AliITSmodule  *mod    The module to be SDgitized
    // Outputs:
    //   none.
    // Return:
    //   none.

    Int_t    number     = 10000;
    Int_t    *frowpixel = new Int_t[number];
    Int_t    *fcolpixel = new Int_t[number];
    Double_t *fenepixel = new Double_t[number];

    // Array of pointers to store the track index of the digits
    // leave +1, otherwise pList crashes when col=256, row=192
    fModule = mod->GetIndex();
    // noise setting
    SetFluctuations(fpList,fModule);

    HitsToAnalogDigits(mod,frowpixel,fcolpixel,fenepixel,fpList);

    // apply mask to SPD module
    SetMask();

    CreateDigit(fModule,fpList);

    // clean memory
    delete[] frowpixel;
    delete[] fcolpixel;
    delete[] fenepixel;
    fMapA2->ClearMap();
    fpList->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSPD::SDigitsToDigits(Int_t module,AliITSpList *pList) {
    // sum digits to Digits.
    // Inputs:
    //   AliITSmodule  *mod    The module to be SDgitized
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.

    if(GetDebug()){
        cout << "Entering AliITSsimulatinSPD::SDigitsToDigits for module=";
        cout << module << endl;
    } // end if GetDebug
    fModule = module;

    // noise setting
    SetFluctuations(pList,module);

    fMapA2->ClearMap(); // since noise is in pList aready. Zero Map so that
    // noise is not doubled when calling FillMapFrompList.

    FillMapFrompList(pList);

    // apply mask to SPD module
    SetMask();

    CreateDigit(module,pList);

    fMapA2->ClearMap();
    pList->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSPD::UpdateMapSignal(Int_t row,Int_t col,Int_t trk,
					  Int_t hit,Int_t mod,Double_t ene,
					  AliITSpList *pList) {
    // updates the Map of signal, adding the energy  (ene) released by
    // the current track
    // Inputs:
    //   Int_t         row  pixel row number
    //   Int_t         col  pixel column number
    //   Int_t         trk  track number which contributed
    //   Int_t         hit  hit number which contributed
    //   Int_t         mod  module number
    //   Double_t      ene  the energy associated with this contribution
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.

    fMapA2->AddSignal(row,col,ene);
    pList->AddSignal(row,col,trk,hit,mod,ene);
}
//______________________________________________________________________
void AliITSsimulationSPD::UpdateMapNoise(Int_t row,Int_t col,Int_t mod,
					 Double_t ene,AliITSpList *pList) {
    // updates the Map of noise, adding the energy  (ene) give my noise
    // Inputs:
    //   Int_t         row  pixel row number
    //   Int_t         col  pixel column number
    //   Int_t         mod  module number
    //   Double_t      ene  the energy associated with this contribution
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.

    fMapA2->AddSignal(row,col,ene);
    pList->AddNoise(row,col,mod,ene);
}
//______________________________________________________________________
void AliITSsimulationSPD::HitsToAnalogDigits(AliITSmodule *mod,
					     Int_t *frowpixel,Int_t *fcolpixel,
					     Double_t *fenepixel,
					     AliITSpList *pList) {
    // Loops over all hits to produce Analog/floting point digits. This
    // is also the first task in producing standard digits.
    // Inputs:
    //   AliITSmodule  *mod        module class
    //   Int_t         *frowpixel  array of pixel rows
    //   Int_t         *fcolpixel  array of pixel columns
    //   Double_t      *fenepiexel array of pixel energies
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.
    
    // loop over hits in the module
    Int_t hitpos,nhits = mod->GetNhits();
    for (hitpos=0;hitpos<nhits;hitpos++) {
        HitToDigit(mod,hitpos,frowpixel,fcolpixel,fenepixel,pList);
    }// end loop over digits
}
//______________________________________________________________________
void AliITSsimulationSPD::HitToDigit(AliITSmodule *mod,Int_t hitpos,
				     Int_t *frowpixel,Int_t *fcolpixel,
				     Double_t *fenepixel,AliITSpList *pList) {
    //  Steering function to determine the digits associated to a given
    // hit (hitpos)
    // The digits are created by charge sharing (ChargeSharing) and by
    // capacitive coupling (SetCoupling). At all the created digits is
    // associated the track number of the hit (ntrack)
    // Inputs:
    //   AliITSmodule  *mod        module class
    //   Int_t         hitpos      hit index value
    //   Int_t         *frowpixel  array of pixel rows
    //   Int_t         *fcolpixel  array of pixel columns
    //   Double_t      *fenepiexel array of pixel energies
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.
    Double_t x1l=0.0,y1l=0.0,z1l=0.0,x2l=0.0,y2l=0.0,z2l=0.0;
    Int_t r1,r2,c1,c2,row,col,npixel = 0;
    Int_t ntrack;
    Double_t ene=0.0,etot=0.0;
    const Float_t kconv = 10000.;     // cm -> microns
    const Float_t kconv1= 0.277e9;    // GeV -> electrons equivalent

    if(!(mod->LineSegmentL(hitpos,x1l,x2l,y1l,y2l,z1l,z2l,etot,ntrack)))return;

    x2l += x1l; y2l += y1l; z2l += z1l; // Convert to ending coordinate.
    // positions shifted and converted in microns
    x1l   = x1l*kconv + fSegmentation->Dx()/2.;
    z1l   = z1l*kconv + fSegmentation->Dz()/2.;
    // positions  shifted and converted in microns
    x2l   = x2l*kconv + fSegmentation->Dx()/2.;
    z2l   = z2l*kconv + fSegmentation->Dz()/2.;
    etot *= kconv1; // convert from GeV to electrons equivalent.
    Int_t module = mod->GetIndex();

    // to account for the effective sensitive area
    // introduced in geometry 
    if (z1l<0 || z1l>fSegmentation->Dz()) return;
    if (z2l<0 || z2l>fSegmentation->Dz()) return;
    if (x1l<0 || x1l>fSegmentation->Dx()) return;
    if (x2l<0 || x2l>fSegmentation->Dx()) return;

    //Get the col and row number starting from 1
    // the x direction is not inverted for the second layer!!!
    fSegmentation->GetPadIxz(x1l, z1l, c1, r1); 
    fSegmentation->GetPadIxz(x2l, z2l, c2, r2);

    // to account for unexpected equal entrance and 
    // exit coordinates
    if (x1l==x2l) x2l=x2l+x2l*0.1;
    if (z1l==z2l) z2l=z2l+z2l*0.1;

    if ((r1==r2) && (c1==c2)){
        // no charge sharing
        npixel = 1;		 
        frowpixel[npixel-1] = r1;
        fcolpixel[npixel-1] = c1;
        fenepixel[npixel-1] = etot;
    } else {
        // charge sharing
        ChargeSharing(x1l,z1l,x2l,z2l,c1,r1,c2,r2,etot,
                      npixel,frowpixel,fcolpixel,fenepixel);
    } // end if r1==r2 && c1==c2.

    for (Int_t npix=0;npix<npixel;npix++){
        row = frowpixel[npix];
        col = fcolpixel[npix];
        ene = fenepixel[npix];
        UpdateMapSignal(row,col,ntrack,hitpos,module,ene,pList); 
        // Starting capacitive coupling effect
        SetCoupling(row,col,ntrack,hitpos,module,pList); 
    } // end for npix
}
//______________________________________________________________________
void AliITSsimulationSPD::ChargeSharing(Float_t x1l,Float_t z1l,Float_t x2l,
					Float_t z2l,Int_t c1,Int_t r1,Int_t c2,
					Int_t r2,Float_t etot,
					Int_t &npixel,Int_t *frowpixel,
					Int_t *fcolpixel,Double_t *fenepixel){
    //  Take into account the geometrical charge sharing when the track
    //  crosses more than one pixel.
    // Inputs:
    //    Float_t  x1l
    //    Float_t  z1l
    //    Float_t  x2l
    //    Float_t  z2l
    //    Int_t    c1
    //    Int_t    r1
    //    Int_t    c2
    //    Int_t    r2
    //    Float_t  etot
    //    Int_t    &npixel
    //   Int_t     *frowpixel  array of pixel rows
    //   Int_t     *fcolpixel  array of pixel columns
    //   Double_t  *fenepiexel array of pixel energies
    // Outputs:
    //    Int_t    &npixel
    // Return:
    //   none.
    //
    //Begin_Html
    /*
      <img src="picts/ITS/barimodel_2.gif">
      </pre>
      <br clear=left>
      <font size=+2 color=red>
      <a href="mailto:Rocco.Caliandro@ba.infn.it"></a>.
      </font>
      <pre>
    */
    //End_Html
    //Float_t dm;
    Float_t xa,za,xb,zb,dx,dz,dtot,refr,refm,refc;
    Float_t refn=0.;
    Float_t arefm, arefr, arefn, arefc, azb, az2l, axb, ax2l;
    Int_t   dirx,dirz,rb,cb;
    Int_t flag,flagrow,flagcol;
    Double_t epar;

    npixel = 0;
    xa     = x1l;
    za     = z1l;
//    dx     = x1l-x2l;
//    dz     = z1l-z2l;
    dx     = x2l-x1l;
    dz     = z2l-z1l;
    dtot   = TMath::Sqrt((dx*dx)+(dz*dz));   
    if (dtot==0.0) dtot = 0.01;
    dirx   = (Int_t) TMath::Sign((Float_t)1,dx);
    dirz   = (Int_t) TMath::Sign((Float_t)1,dz);

    // calculate the x coordinate of  the pixel in the next column    
    // and the z coordinate of  the pixel in the next row
    Float_t xpos, zpos;

    fSegmentation->GetPadCxz(c1, r1-1, xpos, zpos); 

    Float_t xsize = fSegmentation->Dpx(0);
    Float_t zsize = fSegmentation->Dpz(r1-1);
    
    if (dirx == 1) refr = xpos+xsize/2.;
    else refr = xpos-xsize/2.;

    if (dirz == 1) refn = zpos+zsize/2.;
    else refn = zpos-zsize/2.;

    flag = 0;
    flagrow = 0;
    flagcol = 0;
    do{
        // calculate the x coordinate of the intersection with the pixel
        // in the next cell in row  direction
        if(dz!=0)
            refm = dx*((refn - z1l)/dz) + x1l;
        else
            refm = refr+dirx*xsize;
        
        // calculate the z coordinate of the intersection with the pixel
        // in the next cell in column direction
        if (dx!=0)
            refc = dz*((refr - x1l)/dx) + z1l;
        else
            refc = refn+dirz*zsize;
        
        arefm = refm * dirx;
        arefr = refr * dirx;
        arefn = refn * dirz;
        arefc = refc * dirz;
        
        if ((arefm < arefr) && (arefn < arefc)){
            // the track goes in the pixel in the next cell in row direction
            xb = refm;
            zb = refn;
            cb = c1;
            rb = r1 + dirz;
            azb = zb * dirz;
            az2l = z2l * dirz;
            if (rb == r2) flagrow=1;
            if (azb > az2l) {
                zb = z2l;
                xb = x2l;
            } // end if
            // shift to the pixel in the next cell in row direction
            Float_t zsizeNext = fSegmentation->Dpz(rb-1);
            //to account for cell at the borders of the detector
            if(zsizeNext==0) zsizeNext = zsize;
            refn += zsizeNext*dirz;
        }else {
            // the track goes in the pixel in the next cell in column direction
            xb = refr;
            zb = refc;
            cb = c1 + dirx;
            rb = r1;
            axb = xb * dirx;
            ax2l = x2l * dirx;
            if (cb == c2) flagcol=1;
            if (axb > ax2l) {
                zb = z2l;
                xb = x2l;
            } // end ifaxb > ax2l
            
            // shift to the pixel in the next cell in column direction
            Float_t xsizeNext = fSegmentation->Dpx(cb-1);
            //to account for cell at the borders of the detector
            if(xsizeNext==0) xsizeNext = xsize;
            refr += xsizeNext*dirx;
        } // end if (arefm < arefr) && (arefn < arefc)
        
        //calculate the energy lost in the crossed pixel      
        epar = TMath::Sqrt((xb-xa)*(xb-xa)+(zb-za)*(zb-za)); 
        epar = etot*(epar/dtot);
        
        //store row, column and energy lost in the crossed pixel
        frowpixel[npixel] = r1;
        fcolpixel[npixel] = c1;
        fenepixel[npixel] = epar;
        npixel++;
        
        // the exit point of the track is reached
        if (epar == 0) flag = 1;
        if ((r1 == r2) && (c1 == c2)) flag = 1;
        if (flag!=1) {
            r1 = rb;
            c1 = cb;
            xa = xb;
            za = zb;
        } // end if flag!=1
    } while (flag==0);
}
//______________________________________________________________________
void AliITSsimulationSPD::SetCoupling(Int_t row, Int_t col, Int_t ntrack,
				      Int_t idhit,Int_t module,
				      AliITSpList *pList) {
    //  Take into account the coupling between adiacent pixels.
    //  The parameters probcol and probrow are the probability of the
    //  signal in one pixel shared in the two adjacent pixels along
    //  the column and row direction, respectively.
    // Inputs:
    //    Int_t      row    pixel row number
    //    Int_t      col     pixel column number
    //    Int_t      ntrack  track number of track contributing to this signal
    //    Int_t      idhit   hit number of hit contributing to this signal
    //    Int_t      module  module number
    //   AliITSpList *pList  the array of SDigits
    // Outputs:
    //   AliITSpList *pList  the array of SDigits
    // Return:
    //   none.
    //
    //Begin_Html
    /*
      <img src="picts/ITS/barimodel_3.gif">
      </pre>
      <br clear=left>
      <font size=+2 color=red>
      <a href="mailto:tiziano.virgili@cern.ch"></a>.
      </font>
      <pre>
    */
    //End_Html
    Int_t j1,j2,flag=0;
    Double_t pulse1,pulse2;
    Double_t couplR=0.0,couplC=0.0;
    Double_t xr=0.;

    GetCouplings(couplR,couplC);
    j1 = row;
    j2 = col;
    pulse1 = fMapA2->GetSignal(row,col);
    pulse2 = pulse1;
    for (Int_t isign=-1;isign<=1;isign+=2){// loop in row direction
        do{
            j1 += isign;
            //   pulse1 *= couplR; 
            xr = gRandom->Rndm();
            //if ((j1<0) || (j1>GetNPixelsZ()-1) || (pulse1<GetThreshold())){
            if ((j1<0) || (j1>GetNPixelsZ()-1) || (xr>couplR)){
                j1 = row;
                flag = 1;
            }else{
                UpdateMapSignal(j1,col,ntrack,idhit,module,pulse1,pList);
                //  flag = 0;
                flag = 1; // only first next!!
            } // end if
        } while(flag == 0);
        // loop in column direction
        do{
            j2 += isign;
            // pulse2 *= couplC; 
            xr = gRandom->Rndm();
            //if ((j2<0) || (j2>(GetNPixelsX()-1)) || (pulse2<GetThreshold())){
            if ((j2<0) || (j2>GetNPixelsX()-1) || (xr>couplC)){
                j2 = col;
                flag = 1;
            }else{
                UpdateMapSignal(row,j2,ntrack,idhit,module,pulse2,pList);
                //  flag = 0;
                flag = 1; // only first next!!
            } // end if
        } while(flag == 0);
    } // for isign
}
//______________________________________________________________________
void AliITSsimulationSPD::SetCouplingOld(Int_t row, Int_t col, Int_t ntrack,
					 Int_t idhit,Int_t module,
					 AliITSpList *pList) {
    //  Take into account the coupling between adiacent pixels.
    //  The parameters probcol and probrow are the fractions of the
    //  signal in one pixel shared in the two adjacent pixels along
    //  the column and row direction, respectively.
    // Inputs:
    //    Int_t    row    pixel row number
    //    Int_t    col    pixel column number
    //    Int_t    ntrack track number of track contributing to this pixel
    //    Int_t    idhit  hit index number of hit contributing to this pixel
    //    Int_t    module module number
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.
    //
    //Begin_Html
    /*
      <img src="picts/ITS/barimodel_3.gif">
      </pre>
      <br clear=left>
      <font size=+2 color=red>
      <a href="mailto:Rocco.Caliandro@ba.infn.it"></a>.
      </font>
      <pre>
    */
    //End_Html
    Int_t j1,j2,flag=0;
    Double_t pulse1,pulse2;
    Double_t couplR=0.0,couplC=0.0;

    GetCouplings(couplR,couplC);
    j1 = row;
    j2 = col;
    pulse1 = fMapA2->GetSignal(row,col);
    pulse2 = pulse1;
    for (Int_t isign=-1;isign<=1;isign+=2){// loop in row direction
        do{
            j1 += isign;
            pulse1 *= couplR;
            if ((j1<0) || (j1>GetNPixelsZ()-1) || (pulse1<GetThreshold())){
                pulse1 = fMapA2->GetSignal(row,col);
                j1 = row;
                flag = 1;
            }else{
                UpdateMapSignal(j1,col,ntrack,idhit,module,pulse1,pList);
                flag = 0;
            } // end if
        } while(flag == 0);
        // loop in column direction
        do{
            j2 += isign;
            pulse2 *= couplC;
            if ((j2<0) || (j2>(GetNPixelsX()-1)) || (pulse2<GetThreshold())){
                pulse2 = fMapA2->GetSignal(row,col);
                j2 = col;
                flag = 1;
            }else{
                UpdateMapSignal(row,j2,ntrack,idhit,module,pulse2,pList);
                flag = 0;
            } // end if
        } while(flag == 0);
    } // for isign
}
//______________________________________________________________________
void AliITSsimulationSPD::CreateDigit(Int_t module,AliITSpList *pList) {
    // The pixels are fired if the energy deposited inside them is above
    // the threshold parameter ethr. Fired pixed are interpreted as digits
    // and stored in the file digitfilename. One also needs to write out
    // cases when there is only noise (nhits==0).
    // Inputs:
    //    Int_t    module
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.

    static AliITS *aliITS  = (AliITS*)gAlice->GetModule("ITS");

    Int_t size = AliITSdigitSPD::GetNTracks();
    Int_t * digits = new Int_t[size];
    Int_t * tracks = new Int_t[size];
    Int_t * hits = new Int_t[size];
    Float_t * charges = new Float_t[size]; 
    Int_t j1;

    module=0; // remove unused variable warning.
    for(j1=0;j1<size;j1++){tracks[j1]=-3;hits[j1]=-1;charges[j1]=0.0;}
    for (Int_t r=1;r<=GetNPixelsZ();r++) {
        for (Int_t c=1;c<=GetNPixelsX();c++) {
            // check if the deposited energy in a pixel is above the
            // threshold 
            Float_t signal = (Float_t) fMapA2->GetSignal(r,c);
            if ( signal > GetThreshold()) {
                digits[0] = r-1;  // digits starts from 0
                digits[1] = c-1;  // digits starts from 0
                //digits[2] = 1;  
                digits[2] =  (Int_t) signal;  // the signal is stored in
                                              //  electrons
                for(j1=0;j1<size;j1++){
                    if(j1<pList->GetNEnteries()){
                        tracks[j1] = pList->GetTrack(r,c,j1);
                        hits[j1]   = pList->GetHit(r,c,j1);
                        //}else{
                        //tracks[j1] = -3;
                        //hits[j1]   = -1;
                    } // end if
                    //charges[j1] = 0;
                } // end for j1
                Float_t phys = 0;
                aliITS->AddSimDigit(0,phys,digits,tracks,hits,charges);
                if(GetDebug()){
                    cout << " CreateSPDDigit mod=" << fModule << " r,c=" << r;
                    cout <<","<<c<< " sig=" << fpList->GetSignalOnly(r,c);
                    cout << " noise=" << fpList->GetNoise(r,c);
                    cout << " Msig="<< signal << " Thres=" << GetThreshold();
                    cout <<endl;
                }// end if GetDebug
            } // end if of threshold condition
        } // for c
    }// end do on pixels
    delete [] digits;
    delete [] tracks;
    delete [] hits;
    delete [] charges;
}
//______________________________________________________________________
void AliITSsimulationSPD::SetFluctuations(AliITSpList *pList,Int_t module) {
    //  Set the electronic noise and threshold non-uniformities to all the
    //  pixels in a detector.
    //  The parameter fSigma is the squared sum of the sigma due to noise
    //  and the sigma of the threshold distribution among pixels.
    // Inputs:
    //    Int_t      module  modulel number
    //   AliITSpList *pList  the array of SDigits
    // Outputs:
    //   AliITSpList *pList  the array of SDigits
    // Return:
    //   none.
    //
    //Begin_Html
    /*
      <img src="picts/ITS/barimodel_1.gif">
      </pre>
      <br clear=left>
      <font size=+2 color=red>
      <a href="mailto:Rocco.Caliandro@ba.infn.it"></a>.
      </font>
      <pre>
    */
    //End_Html
    Double_t  thr=0.0,sigm=0.0;
    Double_t signal,sigma;
    Int_t iz,ix;

    GetThresholds(thr,sigm);
    sigma = (Double_t) sigm;
    for(iz=1;iz<=GetNPixelsZ();iz++){
        for(ix=1;ix<=GetNPixelsX();ix++){
            signal = sigma*gRandom->Gaus(); 
            fMapA2->SetHit(iz,ix,signal);
            // insert in the label-signal-hit list the pixels fired
            // only by noise
            pList->AddNoise(iz,ix,module,signal);
        } // end of loop on pixels
    } // end of loop on pixels
}
//______________________________________________________________________
void AliITSsimulationSPD::SetMask() {
    //  Apply a mask to the SPD module. 1% of the pixel channels are
    //  masked. When the database will be ready, the masked pixels
    //  should be read from it.
    // Inputs:
    //   none.
    // Outputs:
    //   none.
    // Return:
    //   none.
    Double_t signal;
    Int_t iz,ix,im;
    Float_t totMask;
    Float_t perc = ((AliITSresponseSPD*)fResponse)->GetFractionDead();
    // in this way we get the same set of random numbers for all runs.
    // This is a cluge for now.
    static TRandom *rnd = new TRandom();

    totMask= perc*GetNPixelsZ()*GetNPixelsX();
    for(im=1;im<totMask;im++){
        do{
            ix=(Int_t)(rnd->Rndm()*(GetNPixelsX()-1.) + 1.);
        } while(ix<=0 || ix>GetNPixelsX());
        do{
            iz=(Int_t)(rnd->Rndm()*(GetNPixelsZ()-1.) + 1.);
        } while(iz<=0 || iz>GetNPixelsZ());
        signal = -1.;
        fMapA2->SetHit(iz,ix,signal);
    } // end loop on masked pixels
}
//______________________________________________________________________
void AliITSsimulationSPD::CreateHistograms() {
    // Create Histograms
    // Inputs:
    //   none.
    // Outputs:
    //   none.
    // Return:
    //   none.
    Int_t i;

    fHis=new TObjArray(GetNPixelsZ());
    for(i=0;i<GetNPixelsZ();i++) {
        TString spdname("spd_");
        Char_t candnum[4];
        sprintf(candnum,"%d",i+1);
        spdname.Append(candnum);
        (*fHis)[i] = new TH1F(spdname.Data(),"SPD maps",
                              GetNPixelsX(),0.,(Float_t) GetNPixelsX());
    } // end for i
}
//______________________________________________________________________
void AliITSsimulationSPD::ResetHistograms() {
    // Reset histograms for this detector
    // Inputs:
    //   none.
    // Outputs:
    //   none.
    // Return:
    //   none.
    Int_t i;

    for(i=0;i<GetNPixelsZ();i++ ) {
        if ((*fHis)[i])    ((TH1F*)(*fHis)[i])->Reset();
    } // end for i
}
//______________________________________________________________________
void AliITSsimulationSPD::WriteSDigits(AliITSpList *pList){
    // Fills the Summable digits Tree
    // Inputs:
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.
    Int_t i,ni,j,nj;
    static AliITS *aliITS = (AliITS*)gAlice->GetModule("ITS");

    pList->GetMaxMapIndex(ni,nj);
    for(i=0;i<ni;i++)for(j=0;j<nj;j++){
        if(pList->GetSignalOnly(i,j)>0.0){
            aliITS->AddSumDigit(*(pList->GetpListItem(i,j)));
            if(GetDebug()){
                cout << "pListSPD: " << *(pList->GetpListItem(i,j)) << endl;
                cout << " CreateSPDSDigit mod=" << fModule << " r,c=";
                cout << i  <<","<< j << " sig=" << fpList->GetSignalOnly(i,j);
                cout << " noise=" << fpList->GetNoise(i,j) <<endl;
            } //  end if GetDebug
        } // end if
    } // end for i,j
    return;
}
//______________________________________________________________________
void AliITSsimulationSPD::FillMapFrompList(AliITSpList *pList){
    // Fills fMap2A from the pList of Summable digits
    // Inputs:
    //   AliITSpList   *pList  the array of SDigits
    // Outputs:
    //   AliITSpList   *pList  the array of SDigits
    // Return:
    //   none.
    Int_t ix,iz;

    for(iz=0;iz<GetNPixelsZ();iz++)for(ix=0;ix<GetNPixelsX();ix++) 
        fMapA2->AddSignal(iz,ix,pList->GetSignal(iz,ix));
    return;
}