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a6c02c85 1// @(#) $Id$
2
3// Author: Anders Vestbo <mailto:vestbo@fi.uib.no>
4//*-- Copyright &copy ALICE HLT Group
5
6/** \class AliHLTTPCFitter
7<pre>
8//_____________________________________________________________
9// AliHLTTPCFitter
10//
11// Fit class HLT for helix
12</pre>
13*/
14
15#include <math.h>
a6c02c85 16#include "AliHLTTPCLogging.h"
17#include "AliHLTTPCFitter.h"
18#include "AliHLTTPCVertex.h"
19#include "AliHLTTPCTrack.h"
20#include "AliHLTTPCSpacePointData.h"
21#include "AliHLTTPCMemHandler.h"
22#include "AliHLTTPCTransform.h"
23#include "AliHLTTPC.h"
24
25#if __GNUC__ >= 3
26using namespace std;
27#endif
28
29ClassImp(AliHLTTPCFitter)
30
31
32AliHLTTPCFitter::AliHLTTPCFitter()
33{
34 //constructor
35 fTrack=0;
36 fVertex=0;
37 memset(fClusters,0,36*6*sizeof(AliHLTTPCSpacePointData*));
38}
39
40AliHLTTPCFitter::AliHLTTPCFitter(AliHLTTPCVertex *vertex,Bool_t vertexconstraint)
41{
42 //constructor
43 fTrack=0;
44 fVertex = vertex;
45 fVertexConstraint=vertexconstraint;
46 memset(fClusters,0,36*6*sizeof(AliHLTTPCSpacePointData*));
47}
48
49AliHLTTPCFitter::~AliHLTTPCFitter()
50{
51 //destructor
52 for(Int_t i=0; i<36; i++)
53 {
54 for(Int_t j=0; j<6; j++)
55 {
56 if(fClusters[i][j])
57 delete [] fClusters[i][j];
58 }
59 }
60}
61
62void AliHLTTPCFitter::LoadClusters(Char_t *path,Int_t event,Bool_t sp)
63{
64 //load clusters
65 Char_t fname[256];
66 AliHLTTPCMemHandler *clusterfile[36][6];
67 for(Int_t s=0; s<=35; s++)
68 {
69 for(Int_t p=0; p<6; p++)
70 {
71 Int_t patch;
72 if(sp==kTRUE)
73 patch=-1;
74 else
75 patch=p;
76 if(fClusters[s][p])
77 delete fClusters[s][p];
78 fClusters[s][p] = 0;
79 clusterfile[s][p] = new AliHLTTPCMemHandler();
80 sprintf(fname,"%s/points_%d_%d_%d.raw",path,event,s,patch);
81 if(!clusterfile[s][p]->SetBinaryInput(fname))
82 {
83 delete clusterfile[s][p];
84 clusterfile[s][p] = 0;
85 continue;
86 }
87 fClusters[s][p] = (AliHLTTPCSpacePointData*)clusterfile[s][p]->Allocate();
88 clusterfile[s][p]->Binary2Memory(fNcl[s][p],fClusters[s][p]);
89 clusterfile[s][p]->CloseBinaryInput();
90 if(sp==kTRUE)
91 break;
92 }
93 }
94}
95
96void AliHLTTPCFitter::SortTrackClusters(AliHLTTPCTrack *track) const
97{
98 //Sort the internal cluster list in each track with respect to row numbering.
99 //This may be necessary when no conventional track follower has been
100 //applied, in which the cluster list has been maintained in a more
101 //arbitrary fashion.
102
103 Int_t nhits = track->GetNHits();
104 Int_t *ids = (Int_t*)track->GetHitNumbers();
105 Int_t *origids = new Int_t[nhits];
106 Int_t *mk = new Int_t[nhits];
107 Int_t k;
108
109 for(k=0; k<nhits; k++) {origids[k] = ids[k]; mk[k] = -1;}
110
111 Int_t slice,patch,id,padrow,maxrow,maxk;
112 UInt_t pos;
113 for(Int_t j=0; j<nhits; j++)
114 {
115 maxrow=-1;
116 maxk=200;
117 for(k=0; k<nhits; k++)
118 {
119 id=ids[k];
120 if(id < 0) continue;
121 slice = (id>>25) & 0x7f;
122 patch = (id>>22) & 0x7;
123 pos = id&0x3fffff;
124 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
125 padrow = points[pos].fPadRow;
126 if(padrow > maxrow)
127 {
128 maxrow = padrow;
129 maxk=k;
130 }
131 }
132 mk[j]=maxk;
133 ids[maxk]=-1;
134 }
135
136 for(k=0; k<nhits; k++)
137 ids[k] = origids[mk[k]];
138 delete [] origids;
139 delete [] mk;
140}
141
142Int_t AliHLTTPCFitter::FitHelix(AliHLTTPCTrack *track)
143{
144 //fit helix parameters
145 fTrack = track;
146 if(FitCircle())
147 {
148 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
149 "Problems during circle fit"<<ENDLOG;
150 return 1;
151 }
152 if(FitLine())
153 {
154 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
155 "Problems during line fit"<<ENDLOG;
156 return 1;
157 }
158 return 0;
159}
160
161Int_t AliHLTTPCFitter::FitCircle()
162{
163 //-----------------------------------------------------------------
164 //Fits circle parameters using algorithm
165 //described by ChErnov and Oskov in Computer Physics
166 //Communications.
167 //
168 //Written in FORTRAN by Jawluen Tang, Physics department , UT-Austin
169 //Moved to C by Pablo Yepes
170 //Moved to AliROOT by ASV.
171 //------------------------------------------------------------------
172
173 Double_t wsum = 0.0 ;
174 Double_t xav = 0.0 ;
175 Double_t yav = 0.0 ;
176
177 //
178 // Loop over hits calculating average
179 Double_t * fXYWeight = new Double_t[(fTrack->GetNHits())];
180 UInt_t *hitnum = fTrack->GetHitNumbers();
181 for(Int_t i=0; i<fTrack->GetNHits(); i++)
182 {
183 UInt_t id = hitnum[i];
184 Int_t slice = (id>>25) & 0x7f;
185 Int_t patch = (id>>22) & 0x7;
186 UInt_t pos = id&0x3fffff;
187 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
188 fXYWeight[i] = 1./ (Double_t)(points[pos].fSigmaY2 + points[pos].fSigmaY2);
189 wsum += fXYWeight[i];
190 xav += fXYWeight[i]*points[pos].fX;
191 yav += fXYWeight[i]*points[pos].fY;
192 }
193 if (fVertexConstraint == kTRUE)
194 {
195 wsum += fVertex->GetXYWeight() ;
196 xav += fVertex->GetX() ;
197 yav += fVertex->GetY() ;
198 }
199
200 xav = xav / wsum ;
201 yav = yav / wsum ;
202//
203// CALCULATE <X**2>, <XY>, AND <Y**2> WITH <X> = 0, & <Y> = 0
204//
205 Double_t xxav = 0.0 ;
206 Double_t xyav = 0.0 ;
207 Double_t yyav = 0.0 ;
208 Double_t xi, yi ;
209
210 for(Int_t i=0; i<fTrack->GetNHits(); i++)
211 {
212 UInt_t id = hitnum[i];
213 Int_t slice = (id>>25) & 0x7f;
214 Int_t patch = (id>>22) & 0x7;
215 UInt_t pos = id&0x3fffff;
216 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
217
218 xi = points[pos].fX -xav;
219 yi = points[pos].fY - yav ;
220 xxav += xi * xi * fXYWeight[i];
221 xyav += xi * yi * fXYWeight[i];
222 yyav += yi * yi * fXYWeight[i];
223 }
224
225 if (fVertexConstraint == kTRUE)
226 {
227 xi = fVertex->GetX() - xav ;
228 yi = fVertex->GetY() - yav ;
229 xxav += xi * xi * fVertex->GetXYWeight() ;
230 xyav += xi * yi * fVertex->GetXYWeight() ;
231 yyav += yi * yi * fVertex->GetXYWeight() ;
232 }
233 xxav = xxav / wsum ;
234 xyav = xyav / wsum ;
235 yyav = yyav / wsum ;
236//
237//--> ROTATE COORDINATES SO THAT <XY> = 0
238//
239//--> SIGN(C**2 - S**2) = SIGN(XXAV - YYAV) >
240//--> & > ==> NEW : (XXAV-YYAV) > 0
241//--> SIGN(S) = SIGN(XYAV) >
242
243 Double_t a = fabs( xxav - yyav ) ;
244 Double_t b = 4.0 * xyav * xyav ;
245
246 Double_t asqpb = a * a + b ;
247 Double_t rasqpb = sqrt ( asqpb) ;
248
249 Double_t splus = 1.0 + a / rasqpb ;
250 Double_t sminus = b / (asqpb * splus) ;
251
252 splus = sqrt (0.5 * splus ) ;
253 sminus = sqrt (0.5 * sminus) ;
254//
255//-> FIRST REQUIRE : SIGN(C**2 - S**2) = SIGN(XXAV - YYAV)
256//
257 Double_t sinrot, cosrot ;
258 if ( xxav <= yyav ) {
259 cosrot = sminus ;
260 sinrot = splus ;
261 }
262 else {
263 cosrot = splus ;
264 sinrot = sminus ;
265 }
266//
267//-> REQUIRE : SIGN(S) = SIGN(XYAV) * SIGN(C) (ASSUMING SIGN(C) > 0)
268//
269 if ( xyav < 0.0 ) sinrot = - sinrot ;
270//
271//--> WE NOW HAVE THE SMALLEST ANGLE THAT GUARANTEES <X**2> > <Y**2>
272//--> TO GET THE SIGN OF THE CHARGE RIGHT, THE NEW X-AXIS MUST POINT
273//--> OUTWARD FROM THE ORGIN. WE ARE FREE TO CHANGE SIGNS OF BOTH
274//--> COSROT AND SINROT SIMULTANEOUSLY TO ACCOMPLISH THIS.
275//
276//--> CHOOSE SIGN OF C WISELY TO BE ABLE TO GET THE SIGN OF THE CHARGE
277//
278 if ( cosrot*xav+sinrot*yav < 0.0 ) {
279 cosrot = -cosrot ;
280 sinrot = -sinrot ;
281 }
282//
283//-> NOW GET <R**2> AND RSCALE= SQRT(<R**2>)
284//
285 Double_t rrav = xxav + yyav ;
286 Double_t rscale = sqrt(rrav) ;
287
288 xxav = 0.0 ;
289 yyav = 0.0 ;
290 xyav = 0.0 ;
291 Double_t xrrav = 0.0 ;
292 Double_t yrrav = 0.0 ;
293 Double_t rrrrav = 0.0 ;
294
295 Double_t xixi, yiyi, riri, wiriri, xold, yold ;
296
297 for(Int_t i=0; i<fTrack->GetNHits(); i++)
298 {
299 UInt_t id = hitnum[i];
300 Int_t slice = (id>>25) & 0x7f;
301 Int_t patch = (id>>22) & 0x7;
302 UInt_t pos = id&0x3fffff;
303 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
304
305 xold = points[pos].fX - xav ;
306 yold = points[pos].fY - yav ;
307 //
308 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
309 //
310 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
311 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
312
313 xixi = xi * xi ;
314 yiyi = yi * yi ;
315 riri = xixi + yiyi ;
316 wiriri = fXYWeight[i] * riri ;
317
318 xyav += fXYWeight[i] * xi * yi ;
319 xxav += fXYWeight[i] * xixi ;
320 yyav += fXYWeight[i] * yiyi ;
321
322 xrrav += wiriri * xi ;
323 yrrav += wiriri * yi ;
324 rrrrav += wiriri * riri ;
325 }
326//
327// Include vertex if required
328//
329 if (fVertexConstraint == kTRUE)
330 {
331 xold = fVertex->GetX() - xav ;
332 yold = fVertex->GetY() - yav ;
333 //
334 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
335 //
336 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
337 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
338
339 xixi = xi * xi ;
340 yiyi = yi * yi ;
341 riri = xixi + yiyi ;
342 wiriri = fVertex->GetXYWeight() * riri ;
343
344 xyav += fVertex->GetXYWeight() * xi * yi ;
345 xxav += fVertex->GetXYWeight() * xixi ;
346 yyav += fVertex->GetXYWeight() * yiyi ;
347
348 xrrav += wiriri * xi ;
349 yrrav += wiriri * yi ;
350 rrrrav += wiriri * riri ;
351 }
352 //
353 //
354 //
355 //--> DIVIDE BY WSUM TO MAKE AVERAGES
356 //
357 xxav = xxav / wsum ;
358 yyav = yyav / wsum ;
359 xrrav = xrrav / wsum ;
360 yrrav = yrrav / wsum ;
361 rrrrav = rrrrav / wsum ;
362 xyav = xyav / wsum ;
363
364 Int_t const kntry = 5 ;
365//
366//--> USE THESE TO GET THE COEFFICIENTS OF THE 4-TH ORDER POLYNIMIAL
367//--> DON'T PANIC - THE THIRD ORDER TERM IS ZERO !
368//
369 Double_t xrrxrr = xrrav * xrrav ;
370 Double_t yrryrr = yrrav * yrrav ;
371 Double_t rrrrm1 = rrrrav - 1.0 ;
372 Double_t xxyy = xxav * yyav ;
373
374 Double_t c0 = rrrrm1*xxyy - xrrxrr*yyav - yrryrr*xxav ;
375 Double_t c1 = - rrrrm1 + xrrxrr + yrryrr - 4.0*xxyy ;
376 Double_t c2 = 4.0 + rrrrm1 - 4.0*xxyy ;
377 Double_t c4 = - 4.0 ;
378//
379//--> COEFFICIENTS OF THE DERIVATIVE - USED IN NEWTON-RAPHSON ITERATIONS
380//
381 Double_t c2d = 2.0 * c2 ;
382 Double_t c4d = 4.0 * c4 ;
383//
384//--> 0'TH VALUE OF LAMDA - LINEAR INTERPOLATION BETWEEN P(0) & P(YYAV)
385//
386// LAMDA = YYAV * C0 / (C0 + YRRSQ * (XXAV-YYAV))
387 Double_t lamda = 0.0 ;
388 Double_t dlamda = 0.0 ;
389//
390 Double_t chiscl = wsum * rscale * rscale ;
391 Double_t dlamax = 0.001 / chiscl ;
392
393 Double_t p, pd ;
394 for ( int itry = 1 ; itry <= kntry ; itry++ ) {
395 p = c0 + lamda * (c1 + lamda * (c2 + lamda * lamda * c4 )) ;
396 pd = (c1 + lamda * (c2d + lamda * lamda * c4d)) ;
397 dlamda = -p / pd ;
398 lamda = lamda + dlamda ;
399 if (fabs(dlamda)< dlamax) break ;
400 }
401
402 //Double_t chi2 = (Double_t)(chiscl * lamda) ;
403 //fTrack->SetChiSq1(chi2);
404 // Double_t dchisq = chiscl * dlamda ;
405 //
406 //--> NOW CALCULATE THE MATRIX ELEMENTS FOR ALPHA, BETA & KAPPA
407 //
408 Double_t h11 = xxav - lamda ;
409 Double_t h14 = xrrav ;
410 Double_t h22 = yyav - lamda ;
411 Double_t h24 = yrrav ;
412 Double_t h34 = 1.0 + 2.0*lamda ;
413 if ( h11 == 0.0 || h22 == 0.0 ){
414 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitCircle","TrackFit")<<AliHLTTPCLog::kDec<<
415 "Problems fitting circle"<<ENDLOG;
416 return 1 ;
417 }
418 Double_t rootsq = (h14*h14)/(h11*h11) + 4.0*h34 ;
419
420 Double_t ratio, kappa, beta ;
421 if ( fabs(h22) > fabs(h24) ) {
422 ratio = h24 / h22 ;
423 rootsq = ratio * ratio + rootsq ;
424 kappa = 1.0 / sqrt(rootsq) ;
425 beta = - ratio * kappa ;
426 }
427 else {
428 ratio = h22 / h24 ;
429 rootsq = 1.0 + ratio * ratio * rootsq ;
430 beta = 1.0 / sqrt(rootsq) ;
431 if ( h24 > 0 ) beta = - beta ;
432 kappa = -ratio * beta ;
433 }
434 Double_t alpha = - (h14/h11) * kappa ;
435//
436//--> transform these into the lab coordinate system
437//--> first get kappa and back to real dimensions
438//
439 Double_t kappa1 = kappa / rscale ;
440 Double_t dbro = 0.5 / kappa1 ;
441//
442//--> next rotate alpha and beta and scale
443//
444 Double_t alphar = (cosrot * alpha - sinrot * beta)* dbro ;
445 Double_t betar = (sinrot * alpha + cosrot * beta)* dbro ;
446//
447//--> then translate by (xav,yav)
448//
449 Double_t acent = (double)(xav - alphar) ;
450 Double_t bcent = (double)(yav - betar ) ;
451 Double_t radius = (double)dbro ;
452//
453// Get charge
454//
455 Int_t q = ( ( yrrav < 0 ) ? 1 : -1 ) ;
456 fTrack->SetCharge(q);
457
458 //Set the first point on the track to the space point coordinates of the innermost track
459 //This will be updated to lie on the fit later on (AliHLTTPCTrack::UpdateToFirstPoint).
460 Double_t x0,y0,psi,pt ;
461 Int_t lastid=fTrack->GetNHits()-1;
462 UInt_t id = hitnum[lastid];
463 Int_t slice = (id>>25) & 0x7f;
464 Int_t patch = (id>>22) & 0x7;
465 UInt_t pos = id&0x3fffff;
466 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
467 x0 = points[pos].fX;
468 y0 = points[pos].fY;
469 fTrack->SetFirstPoint(x0,y0,0); //Z-value is set in FitLine
470
471 //Set the remaining fit parameters
472 psi = (Double_t)atan2(bcent-y0,acent-x0) ;
473 psi = psi + q * 0.5F * AliHLTTPCTransform::Pi() ;
474 if ( psi < 0 ) psi = psi + 2*AliHLTTPCTransform::Pi();
475
476 pt = (Double_t)(AliHLTTPCTransform::GetBFact() * AliHLTTPCTransform::GetBField() * radius ) ;
477 fTrack->SetPsi(psi);
478 fTrack->SetPt(pt);
479 fTrack->SetRadius(radius);
480 fTrack->SetCenterX(acent);
481 fTrack->SetCenterY(bcent);
482//
483// Get errors from fast fit
484//
485 //if ( getPara()->getErrors ) getErrorsCircleFit ( acent, bcent, radius ) ;
486//
487 delete [] fXYWeight;
488 return 0 ;
489}
490
491//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
492// Fit Line in s-z plane
493//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
494Int_t AliHLTTPCFitter::FitLine ( )
495{
496 //
497 //Initialization
498 //
499 Double_t sum = 0.F ;
500 Double_t ss = 0.F ;
501 Double_t sz = 0.F ;
502 Double_t sss = 0.F ;
503 Double_t ssz = 0.F ;
504 //
505 //find sum , sums ,sumz, sumss
506 //
507 Double_t dx, dy ;
508 Double_t radius = (Double_t)(fTrack->GetPt() / ( AliHLTTPCTransform::GetBFact() * AliHLTTPCTransform::GetBField() ) ) ;
509
510 Double_t * fS = new Double_t[(fTrack->GetNHits())];
511 Double_t *fZWeight = new Double_t[fTrack->GetNHits()];
512 UInt_t *hitnum = fTrack->GetHitNumbers();
513 if (0)//fVertexConstraint==kTRUE)
514 {
515 UInt_t id = hitnum[0];
516 Int_t slice = (id>>25) & 0x7f;
517 Int_t patch = (id>>22) & 0x7;
518 UInt_t pos = id&0x3fffff;
519 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
520
521 dx = points[pos].fX - fVertex->GetX();
522 dy = points[pos].fY - fVertex->GetY();
523 }
524 else
525 {
526 UInt_t id = hitnum[0];
527 Int_t slice = (id>>25) & 0x7f;
528 Int_t patch = (id>>22) & 0x7;
529 UInt_t posf = id&0x3fffff;
530 AliHLTTPCSpacePointData *pointsf = fClusters[slice][patch];
531 id = hitnum[(fTrack->GetNHits()-1)];
532 slice = (id>>25) & 0x7f;
533 patch = (id>>22) & 0x7;
534 UInt_t posl = id&0x3fffff;
535 AliHLTTPCSpacePointData *pointsl = fClusters[slice][patch];
536 dx = pointsf[posf].fX - pointsl[posl].fX;
537 dy = pointsf[posf].fY - pointsl[posl].fY;
538 }
539
540 Double_t localPsi = 0.5F * sqrt ( dx*dx + dy*dy ) / radius ;
541 Double_t totals ;
542
543 if ( fabs(localPsi) < 1. )
544 {
545 totals = 2.0 * radius * asin ( localPsi ) ;
546 }
547 else
548 {
549 totals = 2.0 * radius * AliHLTTPCTransform::Pi() ;
550 }
551
552 Double_t dpsi,s;
553
554 for(Int_t i=0; i<fTrack->GetNHits(); i++)
555 {
556 UInt_t id = hitnum[i];
557 Int_t slice = (id>>25) & 0x7f;
558 Int_t patch = (id>>22) & 0x7;
559 UInt_t pos = id&0x3fffff;
560 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
561
562 fZWeight[i] = 1./(Double_t)(points[pos].fSigmaZ2);
563 if(i>0)
564 {
565 id = hitnum[i-1];
566 slice = (id>>25) & 0x7f;
567 patch = (id>>22) & 0x7;
568 UInt_t lastpos = id&0x3fffff;
569 AliHLTTPCSpacePointData *lastpoints = fClusters[slice][patch];
570 dx = points[pos].fX -lastpoints[lastpos].fX;
571 dy = points[pos].fY -lastpoints[lastpos].fY;
572 dpsi = 0.5 * (Double_t)sqrt ( dx*dx + dy*dy ) / radius ;
573 if(fabs(dpsi) > 1)
574 return 1;
575 fTrack->SetPsierr(dpsi);
576 s = fS[i-1] - 2.0 * radius * (Double_t)asin ( dpsi ) ;
577 fS[i]=s;
578 }
579 else
580 fS[i]=totals;
581
582 sum += fZWeight[i];
583 ss += fZWeight[i] * fS[i];
584 sz += fZWeight[i] * points[pos].fZ;
585 sss += fZWeight[i] * fS[i] * fS[i];
586 ssz += fZWeight[i] * fS[i] * points[pos].fZ;
587
588 }
589
590
591 Double_t chi2,det = sum * sss - ss * ss;
592 if ( fabs(det) < 1e-20)
593 {
594 chi2 = 99999.F ;
595 //fTrack->SetChiSq2(chi2);
596 return 0 ;
597 }
598
599 //Compute the best fitted parameters A,B
600 Double_t tanl,z0,dtanl,dz0;
601
602 tanl = (Double_t)((sum * ssz - ss * sz ) / det );
603 z0 = (Double_t)((sz * sss - ssz * ss ) / det );
604
605 fTrack->SetTgl(tanl);
606 fTrack->SetZ0(z0);
607
608 //calculate chi-square
609 chi2 = 0.;
610 Double_t r1 ;
611
612 for(Int_t i=0; i<fTrack->GetNHits(); i++)
613 {
614 UInt_t id = hitnum[i];
615 Int_t slice = (id>>25) & 0x7f;
616 Int_t patch = (id>>22) & 0x7;
617 UInt_t pos = id&0x3fffff;
618 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
619 r1 = points[pos].fZ - tanl * fS[i] - z0 ;
620 chi2 += (Double_t) ( (Double_t)(fZWeight[i]) * (r1 * r1) );
621 }
622
623 //fTrack->SetChiSq2(chi2);
624 //
625 //calculate estimated variance
626 //varsq=chi/(double(n)-2.)
627 //calculate covariance matrix
628 //siga=sqrt(varsq*sxx/det)
629 //sigb=sqrt(varsq*sum/det)
630 //
631 dtanl = (Double_t) ( sum / det );
632 dz0 = (Double_t) ( sss / det );
633
634 fTrack->SetTglerr(dtanl);
635 fTrack->SetZ0err(dz0);
636 delete [] fZWeight;
637 delete [] fS;
638 return 0 ;
639}