1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
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10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
18 Revision 1.1 2002/01/21 17:14:21 kowal2
19 New track hits using root containers.
22 ///////////////////////////////////////////////////////////////////////////////
24 // Time Projection Chamber track hits object //
26 // Origin: Marian Ivanov , GSI Darmstadt
29 // Container for Track Hits - based on standard TClonesArray -
30 // fArray of AliTPCTrackHitsParamV2
31 // In AliTPCTrackHitsParamV2 - parameterization of the track segment is stored
32 // for each of the track segment - relative position ( distance between hits) and
33 // charge of the hits is stored - comparing to classical TClonesArray of AliTPChit -
34 // comperssion factor of 5-7 (depending on the required precision) -
35 // In future release AliTPCTrackHitsV2 - will replace old AliTPCTrackHits - which were not
36 // based on standard ROOT containers
38 // // during building Container
39 // AddHitKartez(Int_t volumeID, Int_t trackID, Double_t x, Double_t y, Double_t z,Int_t q)
40 // void SetHitPrecision(Double_t prec) {fPrecision=prec;}
41 // void SetStepPrecision(Double_t prec) {fStep=prec;}
42 // Bool_t FlushHitStack(Bool_t force=kTRUE);
43 // //at the end necessary to have Container in consistent state
45 // // looping over Container
46 // Bool_t First(), Bool_t Next() - iterators - return status of the operation
47 // AliTPChit * GetHit(); - return current hit
52 <img src="gif/AliTPCTrackHitsV2.gif">
57 ///////////////////////////////////////////////////////////////////////////////
59 //#include "TVector3.h"
60 #include "AliTPCTrackHitsV2.h"
62 #include "TClonesArray.h"
69 ClassImp(AliTPCTrackHitsV2)
70 ClassImp(AliTrackHitsParamV2)
73 Int_t AliTrackHitsParamV2::fgCounter1 =0;
74 Int_t AliTrackHitsParamV2::fgCounter2 =0;
76 Int_t AliTPCTrackHitsV2::fgCounter1 =0;
77 Int_t AliTPCTrackHitsV2::fgCounter2 =0;
79 const Double_t AliTPCTrackHitsV2::fgkPrecision=1e-6; //precision
80 const Double_t AliTPCTrackHitsV2::fgkPrecision2=1e-20; //precision
85 struct AliTPCTempHitInfoV2 {
86 enum { fkStackSize = 10000};
87 AliTPCTempHitInfoV2();
88 void NewParam(Double_t r, Double_t z, Double_t fi, Int_t q);
89 void SetHit(Double_t r, Double_t z, Double_t fi, Int_t q);
90 Double_t * GetPosition(Int_t index){return &fPositionStack[index*3];}
91 void UpdateParam(Double_t maxdelta); //recal
92 void Fit2(Double_t fSumY, Double_t fSumYX, Double_t fSumYX2,
93 Double_t fSumX, Double_t fSumX2, Double_t fSumX3,
94 Double_t fSumX4, Int_t n,
95 Double_t &a, Double_t &b, Double_t &c);
96 void Fit(AliTrackHitsParamV2 * param);
102 Double_t fSumDFiDr; //
103 Double_t fSumDFiDr2;//
105 Double_t fSumDZDr; //
106 Double_t fSumDZDr2; //
107 Double_t fOldR; //previos r
108 Double_t fPositionStack[3*fkStackSize]; //position stack
109 UInt_t fQStack[fkStackSize]; //Q stack
110 UInt_t fStackIndex; //current stack index
111 // UInt_t fInfoIndex; //current track info index
112 UInt_t fParamIndex; //current track parameters index
113 // AliTrackHitsInfo * fInfo; //current track info
114 AliTrackHitsParamV2 * fParam; //current track param
118 AliTPCTempHitInfoV2::AliTPCTempHitInfoV2()
121 //set to default value
122 fSumDr=fSumDr2=fSumDr3=fSumDr4=
123 fSumDFi=fSumDFiDr=fSumDFiDr2=
124 fSumDZ=fSumDZDr=fSumDZDr2=0;
131 void AliTPCTempHitInfoV2::NewParam(Double_t r, Double_t z, Double_t fi, Int_t q)
134 //reset stack and sum parameters
135 //store line initial point
136 fSumDr=fSumDr2=fSumDr3=fSumDr4=
137 fSumDFi=fSumDFiDr=fSumDFiDr2=
138 fSumDZ=fSumDZDr=fSumDZDr2=0;
151 void AliTPCTempHitInfoV2::SetHit(Double_t r, Double_t z, Double_t fi, Int_t q)
154 //add hit to the stack
155 //recalculate new estimete of line parameters
156 Double_t *f = GetPosition(fStackIndex);
160 fQStack[fStackIndex]=q;
161 if (fStackIndex==0) return;
162 Double_t dr = (r-fParam->fR);
163 if (TMath::Abs(dr)<AliTPCTrackHitsV2::fgkPrecision) dr =AliTPCTrackHitsV2::fgkPrecision;
164 Double_t dfi = fi-fParam->fFi;
165 Double_t dz = z -fParam->fZ;
167 Double_t dr3 =dr2*dr;
168 Double_t dr4 =dr3*dr;
180 //update fit parameters
182 Double_t det = fSumDr2*fSumDr4-fSumDr3*fSumDr3;
183 if (TMath::Abs(det)<AliTPCTrackHitsV2::fgkPrecision2) return;
184 if ( ( fStackIndex>1 ) ){
185 fParam->fAn = (fSumDr4*fSumDFiDr-fSumDr3*fSumDFiDr2)/det;
186 fParam->fAd = (fSumDr2*fSumDFiDr2-fSumDr3*fSumDFiDr)/det;
189 fParam->fAn = fSumDFiDr/fSumDr2;
190 if ( ( fStackIndex>1 ) ){
191 fParam->fTheta = (fSumDr4*fSumDZDr-fSumDr3*fSumDZDr2)/det;
192 fParam->fThetaD= (fSumDr2*fSumDZDr2-fSumDr3*fSumDZDr)/det;
195 fParam->fTheta = fSumDZDr/fSumDr2;
199 void AliTPCTempHitInfoV2::UpdateParam(Double_t maxdelta)
201 //recalc parameters not fixing origin point
205 Fit2(fSumDFi, fSumDFiDr, fSumDFiDr2, fSumDr,fSumDr2,fSumDr3,fSumDr4,
207 if (TMath::Abs(a)<maxdelta){
208 fParam->fFi +=a/fParam->fR;
212 Fit2(fSumDZ, fSumDZDr, fSumDZDr2, fSumDr,fSumDr2,fSumDr3,fSumDr4,
213 fStackIndex, a,b,c) ;
214 if (TMath::Abs(a)<maxdelta){
222 void AliTPCTempHitInfoV2::Fit2(Double_t fSumY, Double_t fSumYX, Double_t fSumYX2,
223 Double_t fSumX, Double_t fSumX2, Double_t fSumX3,
224 Double_t fSumX4, Int_t n,
225 Double_t &a, Double_t &b, Double_t &c)
227 //fit of second order
229 n* (fSumX2*fSumX4-fSumX3*fSumX3) -
230 fSumX* (fSumX*fSumX4-fSumX3*fSumX2)+
231 fSumX2* (fSumX*fSumX3-fSumX2*fSumX2);
233 if (TMath::Abs(det)> AliTPCTrackHitsV2::fgkPrecision) {
235 (fSumY * (fSumX2*fSumX4-fSumX3*fSumX3)-
236 fSumX *(fSumYX*fSumX4-fSumYX2*fSumX3)+
237 fSumX2*(fSumYX*fSumX3-fSumYX2*fSumX2))/det;
239 (n*(fSumYX*fSumX4-fSumX3*fSumYX2)-
240 fSumY*(fSumX*fSumX4-fSumX3*fSumX2)+
241 fSumX2*(fSumX*fSumYX2-fSumYX*fSumX2))/det;
243 (n*(fSumX2*fSumYX2-fSumYX*fSumX3)-
244 fSumX*(fSumX*fSumYX2-fSumYX*fSumX2)+
245 fSumY*(fSumX*fSumX3-fSumX2*fSumX2))/det;
249 void AliTPCTempHitInfoV2::Fit(AliTrackHitsParamV2 * param)
251 // fit fixing first and the last point
252 //result stored in new param
253 Double_t dx2 = (GetPosition(fStackIndex))[0]-fParam->fR;
254 Double_t det = fSumDr4+dx2*fSumDr2-2*dx2*fSumDr3;
255 if ( (TMath::Abs(det)> AliTPCTrackHitsV2::fgkPrecision) &&
256 ((TMath::Abs(dx2)> AliTPCTrackHitsV2::fgkPrecision))){
257 Double_t dfi2 = (GetPosition(fStackIndex))[1]-fParam->fFi;
258 param->fAd = (fSumDFiDr2+dfi2*fSumDr-dx2*fSumDFiDr-dfi2*fSumDr3/dx2)/det;
259 param->fAn = (dfi2-param->fAd*dx2*dx2)/dx2;
261 Double_t dz2 = (GetPosition(fStackIndex))[1]-fParam->fZ;
262 param->fTheta = (fSumDZDr2+dz2*fSumDr-dx2*fSumDZDr-dz2*fSumDr3/dx2)/det;
263 param->fTheta = (dz2-param->fAd*dx2*dx2)/dx2;
268 AliTrackHitsParamV2::AliTrackHitsParamV2()
270 //default constructor
277 AliTrackHitsParamV2::~AliTrackHitsParamV2()
281 delete[]fHitDistance;
291 AliTPCTrackHitsV2::AliTPCTrackHitsV2()
294 //default constructor
296 const Float_t kHitPrecision=0.002; //default precision for hit position in cm
297 const Float_t kStep =0.003; //30 mum step
298 const UShort_t kMaxDistance =100; //maximum distance 100
300 fPrecision=kHitPrecision; //precision in cm
301 fStep = kStep; //step size
302 fMaxDistance = kMaxDistance; //maximum distance
305 //fTrackHitsInfo = new AliObjectArray("AliTrackHitsInfo");
306 //fTrackHitsParam = new AliObjectArray("AliTrackHitsParamV2");
307 //fHitsPosAndQ = new TArrayOfArrayVStack("AliHitInfo");
308 fArray = new TClonesArray("AliTrackHitsParamV2");
309 fCurrentHit = new AliTPCCurrentHitV2;
318 AliTPCTrackHitsV2::~AliTPCTrackHitsV2()
323 // if (fTrackHitsInfo) delete fTrackHitsInfo;
328 //if (fHitsPosAndQ) delete fHitsPosAndQ;
329 if (fCurrentHit) delete fCurrentHit;
330 if (fTempInfo) delete fTempInfo;
343 void AliTPCTrackHitsV2::Clear()
348 for (Int_t i=0;i<fArray->GetEntriesFast();i++){
349 AliTrackHitsParamV2 * par = (AliTrackHitsParamV2 *)fArray->UncheckedAt(i);
350 par->~AliTrackHitsParamV2(); // delete object
368 void AliTPCTrackHitsV2::AddHitKartez(Int_t volumeID, Int_t trackID, Double_t x,
369 Double_t y, Double_t z,Int_t q)
372 //add hit to the container - it add hit at the end - input in global coordinata
373 Double_t r = TMath::Sqrt(x*x+y*y);
374 Double_t fi = TMath::ACos(x/r);
376 AddHit(volumeID,trackID,r,z,fi,q);
380 void AliTPCTrackHitsV2::AddHit(Int_t volumeID, Int_t trackID,
381 Double_t r, Double_t z, Double_t fi, Int_t q)
386 if (!fTempInfo) { //initialisation of track - initialisation of parameters
387 fTempInfo = new AliTPCTempHitInfoV2;
388 fTempInfo->fParam = new((*fArray)[0]) AliTrackHitsParamV2;
389 fTempInfo->fParam->fVolumeID = volumeID;
390 fTempInfo->fParam->fTrackID = trackID;
393 fTempInfo->fParamIndex = 0;
394 fTempInfo->NewParam(r,z,fi,q);
398 // if new volume or new trackID
399 if ( (volumeID!=fTempInfo->fParam->fVolumeID) ||
400 (trackID!=fTempInfo->fParam->fTrackID)){
401 if (volumeID!=fTempInfo->fParam->fVolumeID) AddVolume(volumeID);
403 FlushHitStack(kTRUE);
405 fTempInfo->fParamIndex++;
406 fTempInfo->fParam = new((*fArray)[fTempInfo->fParamIndex]) AliTrackHitsParamV2;
407 fTempInfo->fParam->fVolumeID = volumeID;
408 fTempInfo->fParam->fTrackID = trackID;
409 fTempInfo->NewParam(r,z,fi,q);
413 //calculate current fit precission to next point
414 AliTrackHitsParamV2 ¶m = *(fTempInfo->fParam);
418 Double_t dr,dz,dfi,ddz,ddfi;
420 dr=dz=dfi=ddz=ddfi=0;
421 drhit = r-fTempInfo->fOldR;
423 //Double_t dfi2 = param.fAn+2*param.fAd*(r-param.fR);
424 Double_t dfi2 = param.fAn;
425 dfi2*=dfi2*fTempInfo->fOldR*fTempInfo->fOldR;
426 //Double_t ddz2 = param.fTheta+2*param.fThetaD*(r-param.fR);
427 Double_t ddz2 = param.fTheta;
429 ratio = TMath::Sqrt(1.+ dfi2+ ddz2);
431 dl = fStep * Short_t(TMath::Nint(drhit*ratio/fStep));
432 ddl = dl - drhit*ratio;
433 fTempInfo->fOldR += dl/ratio;
435 if (fTempInfo->fStackIndex>2){
439 ddz = dr*param.fTheta+dr*dr*param.fThetaD-dz;
440 ddfi= dr*param.fAn+dr*dr*param.fAd-dfi;
441 dd = TMath::Sqrt(ddz*ddz+r*r*ddfi*ddfi+ddl*ddl);
445 if ( ( (dd*1.25>fPrecision) ) ||
446 (fTempInfo->fStackIndex+4>fTempInfo->fkStackSize) ||
447 (TMath::Abs(dl/fStep)>fMaxDistance) )
449 else{ // if precision OK
450 fTempInfo->fStackIndex++;
451 fTempInfo->SetHit(r,z,fi,q);
456 //if parameter changed
457 if (FlushHitStack(kFALSE)){ //if full buffer flushed
458 fTempInfo->fParamIndex++;
459 fTempInfo->fParam = new((*fArray)[fTempInfo->fParamIndex]) AliTrackHitsParamV2;
460 fTempInfo->fParam->fVolumeID = volumeID;
461 fTempInfo->fParam->fTrackID = trackID;
462 fTempInfo->NewParam(r,z,fi,q);
465 fTempInfo->fStackIndex++;
466 fTempInfo->SetHit(r,z,fi,q);
470 Bool_t AliTPCTrackHitsV2::FlushHitStack(Bool_t force)
473 //write fHitsPosAndQ information from the stack to te arrays
474 if (!fTempInfo) return kFALSE;
476 AliTrackHitsParamV2 & param = *(fTempInfo->fParam);
477 //recalculate track parameter not fixing first point
478 fTempInfo->UpdateParam(fStep/4.);
479 //fTempInfo->Fit(fTempInfo->fParam); //- fixing the first and the last point
481 Double_t oldr = param.fR;
484 param.fNHits = fTempInfo->fStackIndex+1;
485 if (param.fHitDistance) delete []param.fHitDistance;
486 if (param.fCharge) delete []param.fCharge;
487 param.fHitDistance = new Short_t[param.fNHits];
488 param.fCharge = new Short_t[param.fNHits];
491 for (i=0; i <= fTempInfo->fStackIndex; i++){
492 Double_t * position = fTempInfo->GetPosition(i);
493 Double_t dr = position[0]-oldr;
496 //Double_t dfi2 = param.fAn+2*param.fAd*(position[0]-param.fR);
497 Double_t dfi2 = param.fAn;
498 dfi2*=dfi2*oldr*oldr;
499 //Double_t ddz2 = param.fTheta+2*param.fThetaD*(position[0]-param.fR);
500 Double_t ddz2 = param.fTheta;
502 ratio = TMath::Sqrt(1.+ dfi2+ ddz2);
505 Double_t dl = fStep*(Short_t)TMath::Nint(dr*ratio/fStep);
508 //calculate precission
509 AliTrackHitsParamV2 ¶m = *(fTempInfo->fParam);
511 Double_t dr1= position[0]-param.fR;
512 Double_t dz = position[1]-param.fZ;
513 Double_t dfi = position[2]-param.fFi;
514 //extrapolated deltas
515 Double_t dr2 = oldr-param.fR;
516 Double_t ddr = dr2-dr1;
517 Double_t ddz = dr2*param.fTheta+dr2*dr2*param.fThetaD-dz;
518 Double_t ddfi= dr2*param.fAn+dr2*dr2*param.fAd-dfi;
519 dd = TMath::Sqrt(ddz*ddz+oldr*oldr*ddfi*ddfi+ddr*ddr);
522 if ( (dd>fPrecision) ){
529 Double_t ddz = dr2*param.fTheta+dr2*dr2*param.fThetaD-dz;
530 Double_t ddfi= dr2*param.fAn+dr2*dr2*param.fAd-dfi;
532 dd = TMath::Sqrt(ddz*ddz+oldr*oldr*ddfi*ddfi+ddr*ddr);
538 param.fHitDistance[i]= Short_t(TMath::Nint(dl/fStep));
539 param.fCharge[i]= Short_t(fTempInfo->fQStack[i]);
542 if (i<=fTempInfo->fStackIndex){ //if previous iteration not succesfull
543 Short_t * charge = new Short_t[i];
544 Short_t * hitDistance= new Short_t[i];
545 memcpy(charge, param.fCharge,sizeof(Short_t)*i);
546 memcpy(hitDistance, param.fHitDistance,sizeof(Short_t)*i);
547 delete [] param.fCharge;
548 delete [] param.fHitDistance;
550 param.fCharge = charge;
551 param.fHitDistance = hitDistance;
553 Int_t volumeID = fTempInfo->fParam->fVolumeID;
554 Int_t trackID =fTempInfo->fParam->fTrackID;
555 fTempInfo->fParamIndex++;
556 fTempInfo->fParam = new((*fArray)[fTempInfo->fParamIndex]) AliTrackHitsParamV2;
557 Double_t * p = fTempInfo->GetPosition(i);
558 UInt_t index2 = fTempInfo->fStackIndex;
559 fTempInfo->NewParam(p[0],p[1],p[2],fTempInfo->fQStack[i]);
560 fTempInfo->fParam->fVolumeID= volumeID;
561 fTempInfo->fParam->fTrackID= trackID;
562 if (i+1<=index2) FlushHitStack2(i+1,index2);
564 if (force) return FlushHitStack(kTRUE);
571 void AliTPCTrackHitsV2::FlushHitStack2(Int_t index1, Int_t index2)
574 // second iteration flush stack
575 // call only for hits where first iteration were not succesfully interpolated
576 Double_t * positionstack = new Double_t[3*(index2-index1+1)];
577 UInt_t * qstack = new UInt_t[index2-index1+1];
578 memcpy(positionstack, &fTempInfo->fPositionStack[3*index1],
579 (3*(index2-index1+1))*sizeof(Double_t));
580 memcpy(qstack, &fTempInfo->fQStack[index1],(index2-index1+1)*sizeof(UInt_t));
581 Double_t *p = positionstack;
582 for (Int_t j=0; j<=index2-index1;j++){
583 fTempInfo->fStackIndex++;
584 fTempInfo->SetHit(p[3*j+0],p[3*j+1],p[3*j+2],qstack[j]);
586 delete []positionstack;
591 void AliTPCTrackHitsV2::AddVolume(Int_t volume)
594 //add volumes to tthe list of volumes
595 Int_t * volumes = new Int_t[fNVolumes+1];
596 if (fVolumes) memcpy(volumes,fVolumes,(fNVolumes+1)*sizeof(Int_t));
597 volumes[fNVolumes]=volume;
599 if (fVolumes) delete []fVolumes;
607 Bool_t AliTPCTrackHitsV2::First()
610 //set Current hit for the first hit
612 AliTrackHitsParamV2 *param = (AliTrackHitsParamV2 *)fArray->At(0);
613 if (!fHit) fHit = new AliTPChit;
615 fCurrentHit->fStatus = kFALSE;
619 fCurrentHit->fParamIndex = 0;
620 fCurrentHit->fStackIndex = 0;
623 ((AliTPChit*)fHit)->fSector = param->fVolumeID;
624 ((AliTPChit*)fHit)->SetTrack(param->fTrackID);
625 ((AliTPChit*)fHit)->SetX(param->fR*TMath::Cos(param->fFi));
626 ((AliTPChit*)fHit)->SetY(param->fR*TMath::Sin(param->fFi));
627 ((AliTPChit*)fHit)->SetZ(param->fZ);
628 ((AliTPChit*)fHit)->fQ = param->fCharge[0];
630 fCurrentHit->fHit.fSector = param->fVolumeID;
631 fCurrentHit->fHit.SetTrack(param->fTrackID);
632 fCurrentHit->fHit.SetX(param->fR*TMath::Cos(param->fFi));
633 fCurrentHit->fHit.SetY(param->fR*TMath::Sin(param->fFi));
634 fCurrentHit->fHit.SetZ(param->fZ);
635 fCurrentHit->fHit.fQ = param->fCharge[0];
637 fCurrentHit->fR = param->fR;
639 return fCurrentHit->fStatus = kTRUE;
642 Bool_t AliTPCTrackHitsV2::Next()
646 if (!(fCurrentHit->fStatus))
649 fCurrentHit->fStackIndex++;
651 AliTrackHitsParamV2 *param = (AliTrackHitsParamV2 *)fArray->At(fCurrentHit->fParamIndex);
652 if (fCurrentHit->fStackIndex>=param->fNHits){
653 fCurrentHit->fParamIndex++;
654 if (fCurrentHit->fParamIndex>=fArray->GetEntriesFast()){
655 fCurrentHit->fStatus=kFALSE;
658 param = (AliTrackHitsParamV2 *)fArray->At(fCurrentHit->fParamIndex);
659 fCurrentHit->fStackIndex=0;
660 fCurrentHit->fR = param->fR;
667 // Double_t dfi2 = param->fAn+2*param->fAd*(fCurrentHit->fR-param->fR);
668 Double_t dfi2 = param->fAn;
669 dfi2*=dfi2*fCurrentHit->fR*fCurrentHit->fR;
670 // Double_t ddz2 = param->fTheta+2*param->fThetaD*(fCurrentHit->fR-param->fR);
671 Double_t ddz2 = param->fTheta;
673 ratio = TMath::Sqrt(1.+ dfi2+ ddz2);
676 fCurrentHit->fR += fStep*param->fHitDistance[fCurrentHit->fStackIndex]/ratio;
678 Double_t dR = fCurrentHit->fR - param->fR;
679 Double_t fi = param->fFi + (param->fAn*dR+param->fAd*dR*dR);
680 Double_t z = param->fZ + (param->fTheta*dR+param->fThetaD*dR*dR);
682 fCurrentHit->fHit.fQ = param->fCharge[fCurrentHit->fStackIndex];
683 fCurrentHit->fHit.SetX(fCurrentHit->fR*TMath::Cos(fi));
684 fCurrentHit->fHit.SetY(fCurrentHit->fR*TMath::Sin(fi));
685 fCurrentHit->fHit.SetZ(z);
686 fCurrentHit->fHit.fSector = param->fVolumeID;
687 fCurrentHit->fHit.SetTrack(param->fTrackID);
689 ((AliTPChit*)fHit)->fQ = param->fCharge[fCurrentHit->fStackIndex];
690 ((AliTPChit*)fHit)->SetX(fCurrentHit->fR*TMath::Cos(fi));
691 ((AliTPChit*)fHit)->SetY(fCurrentHit->fR*TMath::Sin(fi));
692 ((AliTPChit*)fHit)->SetZ(z);
693 ((AliTPChit*)fHit)->fSector = param->fVolumeID;
694 ((AliTPChit*)fHit)->SetTrack(param->fTrackID);
699 AliHit * AliTPCTrackHitsV2::GetHit()
702 return (fCurrentHit->fStatus)? fHit:0;
703 //return &fCurrentHit->fHit;
707 AliTrackHitsParamV2 * AliTPCTrackHitsV2::GetParam()
709 return (fCurrentHit->fStatus)? (AliTrackHitsParamV2 *)fArray->At(fCurrentHit->fParamIndex):0;