+// Double_t s00 = tracklet.GetTrackletSigma2(); // error pad
+// Double_t s11 = 100000; // error pad-row
+// Float_t h01 = tracklet.GetTilt();
+// //
+// // r00 = fCyy + 2*fCzy*h01 + fCzz*h01*h01+s00;
+// r00 = fCyy + fCzz*h01*h01+s00;
+// // r01 = fCzy + fCzz*h01;
+// r01 = fCzy ;
+// r11 = fCzz + s11;
+// det = r00*r11 - r01*r01;
+// // inverse matrix
+// tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
+
+// Double_t k00=fCyy*r00+fCzy*r01, k01=fCyy*r01+fCzy*r11;
+// Double_t k10=fCzy*r00+fCzz*r01, k11=fCzy*r01+fCzz*r11;
+// Double_t k20=fCey*r00+fCez*r01, k21=fCey*r01+fCez*r11;
+// Double_t k30=fCty*r00+fCtz*r01, k31=fCty*r01+fCtz*r11;
+// Double_t k40=fCcy*r00+fCcz*r01, k41=fCcy*r01+fCcz*r11;
+
+// // K matrix
+// // k00=fCyy*r00+fCzy*(r01+h01*r00),k01=fCyy*r01+fCzy*(r11+h01*r01);
+// // k10=fCzy*r00+fCzz*(r01+h01*r00),k11=fCzy*r01+fCzz*(r11+h01*r01);
+// // k20=fCey*r00+fCez*(r01+h01*r00),k21=fCey*r01+fCez*(r11+h01*r01);
+// // k30=fCty*r00+fCtz*(r01+h01*r00),k31=fCty*r01+fCtz*(r11+h01*r01);
+// // k40=fCcy*r00+fCcz*(r01+h01*r00),k41=fCcy*r01+fCcz*(r11+h01*r01);
+// //
+// //Update measurement
+// Double_t cur=fC + k40*dy + k41*dz, eta=fE + k20*dy + k21*dz;
+// // cur=fC + k40*dy + k41*dz; eta=fE + k20*dy + k21*dz;
+// if (TMath::Abs(cur*fX-eta) >= 0.90000) {
+// //Int_t n=GetNumberOfClusters();
+// // if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
+// return 0;
+// }
+// // k01+=h01*k00;
+// // k11+=h01*k10;
+// // k21+=h01*k20;
+// // k31+=h01*k30;
+// // k41+=h01*k40;
+
+
+// fY += k00*dy + k01*dz;
+// fZ += k10*dy + k11*dz;
+// fE = eta;
+// fT += k30*dy + k31*dz;
+// fC = cur;
+
+
+// //Update covariance
+// //
+// //
+// Double_t oldyy = fCyy, oldzz = fCzz; //, oldee=fCee, oldcc =fCcc;
+// Double_t oldzy = fCzy, oldey = fCey, oldty=fCty, oldcy =fCcy;
+// Double_t oldez = fCez, oldtz = fCtz, oldcz=fCcz;
+// //Double_t oldte = fCte, oldce = fCce;
+// //Double_t oldct = fCct;
+
+// fCyy-=k00*oldyy+k01*oldzy;
+// fCzy-=k10*oldyy+k11*oldzy;
+// fCey-=k20*oldyy+k21*oldzy;
+// fCty-=k30*oldyy+k31*oldzy;
+// fCcy-=k40*oldyy+k41*oldzy;
+// //
+// fCzz-=k10*oldzy+k11*oldzz;
+// fCez-=k20*oldzy+k21*oldzz;
+// fCtz-=k30*oldzy+k31*oldzz;
+// fCcz-=k40*oldzy+k41*oldzz;
+// //
+// fCee-=k20*oldey+k21*oldez;
+// fCte-=k30*oldey+k31*oldez;
+// fCce-=k40*oldey+k41*oldez;
+// //
+// fCtt-=k30*oldty+k31*oldtz;
+// fCct-=k40*oldty+k41*oldtz;
+// //
+
+// fCcc-=k40*oldcy+k41*oldcz;
+// //
+
+// //Int_t n=GetNumberOfClusters();
+// //fIndex[n]=index;
+// //SetNumberOfClusters(n+1);