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a6c02c85 1// @(#) $Id$
4aa41877 2// Original: AliHLTFitter.cxx,v 1.14 2005/06/14 10:55:21 cvetan
a6c02c85 3
6235cd38 4/**************************************************************************
5 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
6 * *
7 * Authors: Anders Vestbo *
8 * Matthias Richter <Matthias.Richter@ift.uib.no> *
9 * for The ALICE Off-line Project. *
10 * *
11 * Permission to use, copy, modify and distribute this software and its *
12 * documentation strictly for non-commercial purposes is hereby granted *
13 * without fee, provided that the above copyright notice appears in all *
14 * copies and that both the copyright notice and this permission notice *
15 * appear in the supporting documentation. The authors make no claims *
16 * about the suitability of this software for any purpose. It is *
17 * provided "as is" without express or implied warranty. *
18 **************************************************************************/
19
20/** @file AliHLTTPCFitter.cxx
21 @author Anders Vestbo, maintained by Matthias Richter
22 @date
23 @brief Fit class HLT for helix
a6c02c85 24*/
25
26#include <math.h>
a6c02c85 27#include "AliHLTTPCLogging.h"
28#include "AliHLTTPCFitter.h"
29#include "AliHLTTPCVertex.h"
30#include "AliHLTTPCTrack.h"
31#include "AliHLTTPCSpacePointData.h"
32#include "AliHLTTPCMemHandler.h"
33#include "AliHLTTPCTransform.h"
a7c32962 34//#include "AliHLTTPC.h"
a6c02c85 35
36#if __GNUC__ >= 3
37using namespace std;
38#endif
39
40ClassImp(AliHLTTPCFitter)
41
42
43AliHLTTPCFitter::AliHLTTPCFitter()
6235cd38 44 :
45 fTrack(NULL),
46 fVertex(NULL),
47 fVertexConstraint(0)
a6c02c85 48{
49 //constructor
a6c02c85 50 memset(fClusters,0,36*6*sizeof(AliHLTTPCSpacePointData*));
6235cd38 51 memset(fNcl,0,36*6*sizeof(UInt_t));
52}
53
54AliHLTTPCFitter::AliHLTTPCFitter(const AliHLTTPCFitter& src)
55 :
56 fTrack(NULL),
57 fVertex(NULL),
58 fVertexConstraint(0)
59{
60 // dummy copy constructor according to eff C++
61 memset(fClusters,0,36*6*sizeof(AliHLTTPCSpacePointData*));
62 memset(fNcl,0,36*6*sizeof(UInt_t));
63}
64
65AliHLTTPCFitter& AliHLTTPCFitter::operator=(const AliHLTTPCFitter& src)
66{
67 // dummy assignment operator according to eff C++
68 return *this;
a6c02c85 69}
70
71AliHLTTPCFitter::AliHLTTPCFitter(AliHLTTPCVertex *vertex,Bool_t vertexconstraint)
72{
73 //constructor
74 fTrack=0;
75 fVertex = vertex;
76 fVertexConstraint=vertexconstraint;
77 memset(fClusters,0,36*6*sizeof(AliHLTTPCSpacePointData*));
78}
79
80AliHLTTPCFitter::~AliHLTTPCFitter()
81{
82 //destructor
83 for(Int_t i=0; i<36; i++)
84 {
85 for(Int_t j=0; j<6; j++)
86 {
87 if(fClusters[i][j])
88 delete [] fClusters[i][j];
89 }
90 }
91}
92
93void AliHLTTPCFitter::LoadClusters(Char_t *path,Int_t event,Bool_t sp)
94{
95 //load clusters
96 Char_t fname[256];
97 AliHLTTPCMemHandler *clusterfile[36][6];
98 for(Int_t s=0; s<=35; s++)
99 {
100 for(Int_t p=0; p<6; p++)
101 {
102 Int_t patch;
103 if(sp==kTRUE)
104 patch=-1;
105 else
106 patch=p;
107 if(fClusters[s][p])
108 delete fClusters[s][p];
109 fClusters[s][p] = 0;
110 clusterfile[s][p] = new AliHLTTPCMemHandler();
111 sprintf(fname,"%s/points_%d_%d_%d.raw",path,event,s,patch);
112 if(!clusterfile[s][p]->SetBinaryInput(fname))
113 {
114 delete clusterfile[s][p];
115 clusterfile[s][p] = 0;
116 continue;
117 }
118 fClusters[s][p] = (AliHLTTPCSpacePointData*)clusterfile[s][p]->Allocate();
119 clusterfile[s][p]->Binary2Memory(fNcl[s][p],fClusters[s][p]);
120 clusterfile[s][p]->CloseBinaryInput();
121 if(sp==kTRUE)
122 break;
123 }
124 }
125}
126
127void AliHLTTPCFitter::SortTrackClusters(AliHLTTPCTrack *track) const
128{
129 //Sort the internal cluster list in each track with respect to row numbering.
130 //This may be necessary when no conventional track follower has been
131 //applied, in which the cluster list has been maintained in a more
132 //arbitrary fashion.
133
134 Int_t nhits = track->GetNHits();
135 Int_t *ids = (Int_t*)track->GetHitNumbers();
136 Int_t *origids = new Int_t[nhits];
137 Int_t *mk = new Int_t[nhits];
138 Int_t k;
139
140 for(k=0; k<nhits; k++) {origids[k] = ids[k]; mk[k] = -1;}
141
142 Int_t slice,patch,id,padrow,maxrow,maxk;
143 UInt_t pos;
144 for(Int_t j=0; j<nhits; j++)
145 {
146 maxrow=-1;
147 maxk=200;
148 for(k=0; k<nhits; k++)
149 {
150 id=ids[k];
151 if(id < 0) continue;
152 slice = (id>>25) & 0x7f;
153 patch = (id>>22) & 0x7;
154 pos = id&0x3fffff;
155 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
156 padrow = points[pos].fPadRow;
157 if(padrow > maxrow)
158 {
159 maxrow = padrow;
160 maxk=k;
161 }
162 }
163 mk[j]=maxk;
164 ids[maxk]=-1;
165 }
166
167 for(k=0; k<nhits; k++)
168 ids[k] = origids[mk[k]];
169 delete [] origids;
170 delete [] mk;
171}
172
173Int_t AliHLTTPCFitter::FitHelix(AliHLTTPCTrack *track)
174{
175 //fit helix parameters
176 fTrack = track;
177 if(FitCircle())
178 {
179 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
180 "Problems during circle fit"<<ENDLOG;
181 return 1;
182 }
183 if(FitLine())
184 {
185 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
186 "Problems during line fit"<<ENDLOG;
187 return 1;
188 }
189 return 0;
190}
191
192Int_t AliHLTTPCFitter::FitCircle()
193{
194 //-----------------------------------------------------------------
195 //Fits circle parameters using algorithm
196 //described by ChErnov and Oskov in Computer Physics
197 //Communications.
198 //
199 //Written in FORTRAN by Jawluen Tang, Physics department , UT-Austin
200 //Moved to C by Pablo Yepes
201 //Moved to AliROOT by ASV.
202 //------------------------------------------------------------------
203
204 Double_t wsum = 0.0 ;
205 Double_t xav = 0.0 ;
206 Double_t yav = 0.0 ;
207
208 //
209 // Loop over hits calculating average
210 Double_t * fXYWeight = new Double_t[(fTrack->GetNHits())];
211 UInt_t *hitnum = fTrack->GetHitNumbers();
212 for(Int_t i=0; i<fTrack->GetNHits(); i++)
213 {
214 UInt_t id = hitnum[i];
215 Int_t slice = (id>>25) & 0x7f;
216 Int_t patch = (id>>22) & 0x7;
217 UInt_t pos = id&0x3fffff;
218 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
219 fXYWeight[i] = 1./ (Double_t)(points[pos].fSigmaY2 + points[pos].fSigmaY2);
220 wsum += fXYWeight[i];
221 xav += fXYWeight[i]*points[pos].fX;
222 yav += fXYWeight[i]*points[pos].fY;
223 }
224 if (fVertexConstraint == kTRUE)
225 {
226 wsum += fVertex->GetXYWeight() ;
227 xav += fVertex->GetX() ;
228 yav += fVertex->GetY() ;
229 }
230
231 xav = xav / wsum ;
232 yav = yav / wsum ;
233//
234// CALCULATE <X**2>, <XY>, AND <Y**2> WITH <X> = 0, & <Y> = 0
235//
236 Double_t xxav = 0.0 ;
237 Double_t xyav = 0.0 ;
238 Double_t yyav = 0.0 ;
239 Double_t xi, yi ;
240
241 for(Int_t i=0; i<fTrack->GetNHits(); i++)
242 {
243 UInt_t id = hitnum[i];
244 Int_t slice = (id>>25) & 0x7f;
245 Int_t patch = (id>>22) & 0x7;
246 UInt_t pos = id&0x3fffff;
247 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
248
249 xi = points[pos].fX -xav;
250 yi = points[pos].fY - yav ;
251 xxav += xi * xi * fXYWeight[i];
252 xyav += xi * yi * fXYWeight[i];
253 yyav += yi * yi * fXYWeight[i];
254 }
255
256 if (fVertexConstraint == kTRUE)
257 {
258 xi = fVertex->GetX() - xav ;
259 yi = fVertex->GetY() - yav ;
260 xxav += xi * xi * fVertex->GetXYWeight() ;
261 xyav += xi * yi * fVertex->GetXYWeight() ;
262 yyav += yi * yi * fVertex->GetXYWeight() ;
263 }
264 xxav = xxav / wsum ;
265 xyav = xyav / wsum ;
266 yyav = yyav / wsum ;
267//
268//--> ROTATE COORDINATES SO THAT <XY> = 0
269//
270//--> SIGN(C**2 - S**2) = SIGN(XXAV - YYAV) >
271//--> & > ==> NEW : (XXAV-YYAV) > 0
272//--> SIGN(S) = SIGN(XYAV) >
273
274 Double_t a = fabs( xxav - yyav ) ;
275 Double_t b = 4.0 * xyav * xyav ;
276
277 Double_t asqpb = a * a + b ;
278 Double_t rasqpb = sqrt ( asqpb) ;
279
280 Double_t splus = 1.0 + a / rasqpb ;
281 Double_t sminus = b / (asqpb * splus) ;
282
283 splus = sqrt (0.5 * splus ) ;
284 sminus = sqrt (0.5 * sminus) ;
285//
286//-> FIRST REQUIRE : SIGN(C**2 - S**2) = SIGN(XXAV - YYAV)
287//
288 Double_t sinrot, cosrot ;
289 if ( xxav <= yyav ) {
290 cosrot = sminus ;
291 sinrot = splus ;
292 }
293 else {
294 cosrot = splus ;
295 sinrot = sminus ;
296 }
297//
298//-> REQUIRE : SIGN(S) = SIGN(XYAV) * SIGN(C) (ASSUMING SIGN(C) > 0)
299//
300 if ( xyav < 0.0 ) sinrot = - sinrot ;
301//
302//--> WE NOW HAVE THE SMALLEST ANGLE THAT GUARANTEES <X**2> > <Y**2>
303//--> TO GET THE SIGN OF THE CHARGE RIGHT, THE NEW X-AXIS MUST POINT
304//--> OUTWARD FROM THE ORGIN. WE ARE FREE TO CHANGE SIGNS OF BOTH
305//--> COSROT AND SINROT SIMULTANEOUSLY TO ACCOMPLISH THIS.
306//
307//--> CHOOSE SIGN OF C WISELY TO BE ABLE TO GET THE SIGN OF THE CHARGE
308//
309 if ( cosrot*xav+sinrot*yav < 0.0 ) {
310 cosrot = -cosrot ;
311 sinrot = -sinrot ;
312 }
313//
314//-> NOW GET <R**2> AND RSCALE= SQRT(<R**2>)
315//
316 Double_t rrav = xxav + yyav ;
317 Double_t rscale = sqrt(rrav) ;
318
319 xxav = 0.0 ;
320 yyav = 0.0 ;
321 xyav = 0.0 ;
322 Double_t xrrav = 0.0 ;
323 Double_t yrrav = 0.0 ;
324 Double_t rrrrav = 0.0 ;
325
326 Double_t xixi, yiyi, riri, wiriri, xold, yold ;
327
328 for(Int_t i=0; i<fTrack->GetNHits(); i++)
329 {
330 UInt_t id = hitnum[i];
331 Int_t slice = (id>>25) & 0x7f;
332 Int_t patch = (id>>22) & 0x7;
333 UInt_t pos = id&0x3fffff;
334 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
335
336 xold = points[pos].fX - xav ;
337 yold = points[pos].fY - yav ;
338 //
339 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
340 //
341 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
342 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
343
344 xixi = xi * xi ;
345 yiyi = yi * yi ;
346 riri = xixi + yiyi ;
347 wiriri = fXYWeight[i] * riri ;
348
349 xyav += fXYWeight[i] * xi * yi ;
350 xxav += fXYWeight[i] * xixi ;
351 yyav += fXYWeight[i] * yiyi ;
352
353 xrrav += wiriri * xi ;
354 yrrav += wiriri * yi ;
355 rrrrav += wiriri * riri ;
356 }
357//
358// Include vertex if required
359//
360 if (fVertexConstraint == kTRUE)
361 {
362 xold = fVertex->GetX() - xav ;
363 yold = fVertex->GetY() - yav ;
364 //
365 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
366 //
367 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
368 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
369
370 xixi = xi * xi ;
371 yiyi = yi * yi ;
372 riri = xixi + yiyi ;
373 wiriri = fVertex->GetXYWeight() * riri ;
374
375 xyav += fVertex->GetXYWeight() * xi * yi ;
376 xxav += fVertex->GetXYWeight() * xixi ;
377 yyav += fVertex->GetXYWeight() * yiyi ;
378
379 xrrav += wiriri * xi ;
380 yrrav += wiriri * yi ;
381 rrrrav += wiriri * riri ;
382 }
383 //
384 //
385 //
386 //--> DIVIDE BY WSUM TO MAKE AVERAGES
387 //
388 xxav = xxav / wsum ;
389 yyav = yyav / wsum ;
390 xrrav = xrrav / wsum ;
391 yrrav = yrrav / wsum ;
392 rrrrav = rrrrav / wsum ;
393 xyav = xyav / wsum ;
394
395 Int_t const kntry = 5 ;
396//
397//--> USE THESE TO GET THE COEFFICIENTS OF THE 4-TH ORDER POLYNIMIAL
398//--> DON'T PANIC - THE THIRD ORDER TERM IS ZERO !
399//
400 Double_t xrrxrr = xrrav * xrrav ;
401 Double_t yrryrr = yrrav * yrrav ;
402 Double_t rrrrm1 = rrrrav - 1.0 ;
403 Double_t xxyy = xxav * yyav ;
404
405 Double_t c0 = rrrrm1*xxyy - xrrxrr*yyav - yrryrr*xxav ;
406 Double_t c1 = - rrrrm1 + xrrxrr + yrryrr - 4.0*xxyy ;
407 Double_t c2 = 4.0 + rrrrm1 - 4.0*xxyy ;
408 Double_t c4 = - 4.0 ;
409//
410//--> COEFFICIENTS OF THE DERIVATIVE - USED IN NEWTON-RAPHSON ITERATIONS
411//
412 Double_t c2d = 2.0 * c2 ;
413 Double_t c4d = 4.0 * c4 ;
414//
415//--> 0'TH VALUE OF LAMDA - LINEAR INTERPOLATION BETWEEN P(0) & P(YYAV)
416//
417// LAMDA = YYAV * C0 / (C0 + YRRSQ * (XXAV-YYAV))
418 Double_t lamda = 0.0 ;
419 Double_t dlamda = 0.0 ;
420//
421 Double_t chiscl = wsum * rscale * rscale ;
422 Double_t dlamax = 0.001 / chiscl ;
423
424 Double_t p, pd ;
425 for ( int itry = 1 ; itry <= kntry ; itry++ ) {
426 p = c0 + lamda * (c1 + lamda * (c2 + lamda * lamda * c4 )) ;
427 pd = (c1 + lamda * (c2d + lamda * lamda * c4d)) ;
428 dlamda = -p / pd ;
429 lamda = lamda + dlamda ;
430 if (fabs(dlamda)< dlamax) break ;
431 }
432
433 //Double_t chi2 = (Double_t)(chiscl * lamda) ;
434 //fTrack->SetChiSq1(chi2);
435 // Double_t dchisq = chiscl * dlamda ;
436 //
437 //--> NOW CALCULATE THE MATRIX ELEMENTS FOR ALPHA, BETA & KAPPA
438 //
439 Double_t h11 = xxav - lamda ;
440 Double_t h14 = xrrav ;
441 Double_t h22 = yyav - lamda ;
442 Double_t h24 = yrrav ;
443 Double_t h34 = 1.0 + 2.0*lamda ;
444 if ( h11 == 0.0 || h22 == 0.0 ){
445 LOG(AliHLTTPCLog::kError,"AliHLTTPCFitter::FitCircle","TrackFit")<<AliHLTTPCLog::kDec<<
446 "Problems fitting circle"<<ENDLOG;
447 return 1 ;
448 }
449 Double_t rootsq = (h14*h14)/(h11*h11) + 4.0*h34 ;
450
451 Double_t ratio, kappa, beta ;
452 if ( fabs(h22) > fabs(h24) ) {
453 ratio = h24 / h22 ;
454 rootsq = ratio * ratio + rootsq ;
455 kappa = 1.0 / sqrt(rootsq) ;
456 beta = - ratio * kappa ;
457 }
458 else {
459 ratio = h22 / h24 ;
460 rootsq = 1.0 + ratio * ratio * rootsq ;
461 beta = 1.0 / sqrt(rootsq) ;
462 if ( h24 > 0 ) beta = - beta ;
463 kappa = -ratio * beta ;
464 }
465 Double_t alpha = - (h14/h11) * kappa ;
466//
467//--> transform these into the lab coordinate system
468//--> first get kappa and back to real dimensions
469//
470 Double_t kappa1 = kappa / rscale ;
471 Double_t dbro = 0.5 / kappa1 ;
472//
473//--> next rotate alpha and beta and scale
474//
475 Double_t alphar = (cosrot * alpha - sinrot * beta)* dbro ;
476 Double_t betar = (sinrot * alpha + cosrot * beta)* dbro ;
477//
478//--> then translate by (xav,yav)
479//
480 Double_t acent = (double)(xav - alphar) ;
481 Double_t bcent = (double)(yav - betar ) ;
482 Double_t radius = (double)dbro ;
483//
484// Get charge
485//
486 Int_t q = ( ( yrrav < 0 ) ? 1 : -1 ) ;
487 fTrack->SetCharge(q);
488
489 //Set the first point on the track to the space point coordinates of the innermost track
490 //This will be updated to lie on the fit later on (AliHLTTPCTrack::UpdateToFirstPoint).
491 Double_t x0,y0,psi,pt ;
492 Int_t lastid=fTrack->GetNHits()-1;
493 UInt_t id = hitnum[lastid];
494 Int_t slice = (id>>25) & 0x7f;
495 Int_t patch = (id>>22) & 0x7;
496 UInt_t pos = id&0x3fffff;
497 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
498 x0 = points[pos].fX;
499 y0 = points[pos].fY;
500 fTrack->SetFirstPoint(x0,y0,0); //Z-value is set in FitLine
501
502 //Set the remaining fit parameters
503 psi = (Double_t)atan2(bcent-y0,acent-x0) ;
504 psi = psi + q * 0.5F * AliHLTTPCTransform::Pi() ;
505 if ( psi < 0 ) psi = psi + 2*AliHLTTPCTransform::Pi();
506
507 pt = (Double_t)(AliHLTTPCTransform::GetBFact() * AliHLTTPCTransform::GetBField() * radius ) ;
508 fTrack->SetPsi(psi);
509 fTrack->SetPt(pt);
510 fTrack->SetRadius(radius);
511 fTrack->SetCenterX(acent);
512 fTrack->SetCenterY(bcent);
513//
514// Get errors from fast fit
515//
516 //if ( getPara()->getErrors ) getErrorsCircleFit ( acent, bcent, radius ) ;
517//
518 delete [] fXYWeight;
519 return 0 ;
520}
521
522//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
523// Fit Line in s-z plane
524//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
525Int_t AliHLTTPCFitter::FitLine ( )
526{
527 //
528 //Initialization
529 //
530 Double_t sum = 0.F ;
531 Double_t ss = 0.F ;
532 Double_t sz = 0.F ;
533 Double_t sss = 0.F ;
534 Double_t ssz = 0.F ;
535 //
536 //find sum , sums ,sumz, sumss
537 //
538 Double_t dx, dy ;
539 Double_t radius = (Double_t)(fTrack->GetPt() / ( AliHLTTPCTransform::GetBFact() * AliHLTTPCTransform::GetBField() ) ) ;
540
541 Double_t * fS = new Double_t[(fTrack->GetNHits())];
542 Double_t *fZWeight = new Double_t[fTrack->GetNHits()];
543 UInt_t *hitnum = fTrack->GetHitNumbers();
544 if (0)//fVertexConstraint==kTRUE)
545 {
546 UInt_t id = hitnum[0];
547 Int_t slice = (id>>25) & 0x7f;
548 Int_t patch = (id>>22) & 0x7;
549 UInt_t pos = id&0x3fffff;
550 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
551
552 dx = points[pos].fX - fVertex->GetX();
553 dy = points[pos].fY - fVertex->GetY();
554 }
555 else
556 {
557 UInt_t id = hitnum[0];
558 Int_t slice = (id>>25) & 0x7f;
559 Int_t patch = (id>>22) & 0x7;
560 UInt_t posf = id&0x3fffff;
561 AliHLTTPCSpacePointData *pointsf = fClusters[slice][patch];
562 id = hitnum[(fTrack->GetNHits()-1)];
563 slice = (id>>25) & 0x7f;
564 patch = (id>>22) & 0x7;
565 UInt_t posl = id&0x3fffff;
566 AliHLTTPCSpacePointData *pointsl = fClusters[slice][patch];
567 dx = pointsf[posf].fX - pointsl[posl].fX;
568 dy = pointsf[posf].fY - pointsl[posl].fY;
569 }
570
571 Double_t localPsi = 0.5F * sqrt ( dx*dx + dy*dy ) / radius ;
572 Double_t totals ;
573
574 if ( fabs(localPsi) < 1. )
575 {
576 totals = 2.0 * radius * asin ( localPsi ) ;
577 }
578 else
579 {
580 totals = 2.0 * radius * AliHLTTPCTransform::Pi() ;
581 }
582
583 Double_t dpsi,s;
584
585 for(Int_t i=0; i<fTrack->GetNHits(); i++)
586 {
587 UInt_t id = hitnum[i];
588 Int_t slice = (id>>25) & 0x7f;
589 Int_t patch = (id>>22) & 0x7;
590 UInt_t pos = id&0x3fffff;
591 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
592
593 fZWeight[i] = 1./(Double_t)(points[pos].fSigmaZ2);
594 if(i>0)
595 {
596 id = hitnum[i-1];
597 slice = (id>>25) & 0x7f;
598 patch = (id>>22) & 0x7;
599 UInt_t lastpos = id&0x3fffff;
600 AliHLTTPCSpacePointData *lastpoints = fClusters[slice][patch];
601 dx = points[pos].fX -lastpoints[lastpos].fX;
602 dy = points[pos].fY -lastpoints[lastpos].fY;
603 dpsi = 0.5 * (Double_t)sqrt ( dx*dx + dy*dy ) / radius ;
604 if(fabs(dpsi) > 1)
605 return 1;
606 fTrack->SetPsierr(dpsi);
607 s = fS[i-1] - 2.0 * radius * (Double_t)asin ( dpsi ) ;
608 fS[i]=s;
609 }
610 else
611 fS[i]=totals;
612
613 sum += fZWeight[i];
614 ss += fZWeight[i] * fS[i];
615 sz += fZWeight[i] * points[pos].fZ;
616 sss += fZWeight[i] * fS[i] * fS[i];
617 ssz += fZWeight[i] * fS[i] * points[pos].fZ;
618
619 }
620
621
622 Double_t chi2,det = sum * sss - ss * ss;
623 if ( fabs(det) < 1e-20)
624 {
625 chi2 = 99999.F ;
626 //fTrack->SetChiSq2(chi2);
627 return 0 ;
628 }
629
630 //Compute the best fitted parameters A,B
631 Double_t tanl,z0,dtanl,dz0;
632
633 tanl = (Double_t)((sum * ssz - ss * sz ) / det );
634 z0 = (Double_t)((sz * sss - ssz * ss ) / det );
635
636 fTrack->SetTgl(tanl);
637 fTrack->SetZ0(z0);
638
639 //calculate chi-square
640 chi2 = 0.;
641 Double_t r1 ;
642
643 for(Int_t i=0; i<fTrack->GetNHits(); i++)
644 {
645 UInt_t id = hitnum[i];
646 Int_t slice = (id>>25) & 0x7f;
647 Int_t patch = (id>>22) & 0x7;
648 UInt_t pos = id&0x3fffff;
649 AliHLTTPCSpacePointData *points = fClusters[slice][patch];
650 r1 = points[pos].fZ - tanl * fS[i] - z0 ;
651 chi2 += (Double_t) ( (Double_t)(fZWeight[i]) * (r1 * r1) );
652 }
653
654 //fTrack->SetChiSq2(chi2);
655 //
656 //calculate estimated variance
657 //varsq=chi/(double(n)-2.)
658 //calculate covariance matrix
659 //siga=sqrt(varsq*sxx/det)
660 //sigb=sqrt(varsq*sum/det)
661 //
662 dtanl = (Double_t) ( sum / det );
663 dz0 = (Double_t) ( sss / det );
664
665 fTrack->SetTglerr(dtanl);
666 fTrack->SetZ0err(dz0);
667 delete [] fZWeight;
668 delete [] fS;
669 return 0 ;
670}