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shahor02 merged 1 commit into from
Mar 12, 2026
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Methods for Barrel <-> Forward tracks conversion #15150

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12 changes: 12 additions & 0 deletions DataFormats/Reconstruction/include/ReconstructionDataFormats/TrackFwd.h
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Expand Up @@ -31,6 +31,12 @@ using SMatrix55Sym = ROOT::Math::SMatrix<double, 5, 5, ROOT::Math::MatRepSym<dou
using SMatrix55Std = ROOT::Math::SMatrix<double, 5>;
using SMatrix5 = ROOT::Math::SVector<Double_t, 5>;

template <typename value_T>
class TrackParametrization; // fwd declaration for conversion method

template <typename value_T>
class TrackParametrizationWithError; // fwd declaration for conversion method

class TrackParFwd
{ // Forward track parameterization, kinematics only.
public:
Expand All @@ -42,6 +48,9 @@ class TrackParFwd
TrackParFwd(TrackParFwd&&) = delete;
TrackParFwd& operator=(TrackParFwd&&) = delete;

template <typename T>
void toBarrelTrackPar(TrackParametrization<T>& t) const;

/// return Z coordinate (cm)
Double_t getZ() const { return mZ; }
/// set Z coordinate (cm)
Expand Down Expand Up @@ -145,6 +154,9 @@ class TrackParCovFwd : public TrackParFwd
TrackParCovFwd& operator=(const TrackParCovFwd& tpf) = default;
TrackParCovFwd(const Double_t z, const SMatrix5& parameters, const SMatrix55Sym& covariances, const Double_t chi2);

template <typename T>
void toBarrelTrackParCov(TrackParametrizationWithError<T>& t) const;

const SMatrix55Sym& getCovariances() const { return mCovariances; }
void setCovariances(const SMatrix55Sym& covariances) { mCovariances = covariances; }
void deleteCovariances() { mCovariances = SMatrix55Sym(); }
Expand Down
4 changes: 4 additions & 0 deletions DataFormats/Reconstruction/include/ReconstructionDataFormats/TrackParametrization.h
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Expand Up @@ -66,6 +66,9 @@ class DCA;

namespace track
{

class TrackParFwd; // fwd declaration for conversion method

// aliases for track elements
enum ParLabels : int { kY,
kZ,
Expand Down Expand Up @@ -252,6 +255,7 @@ class TrackParametrization
GPUd() void printParam() const;
GPUd() void printParamHexadecimal();
#ifndef GPUCA_ALIGPUCODE
void toFwdTrackPar(TrackParFwd& t) const;
std::string asString() const;
std::string asStringHexadecimal();
size_t hash() const { return hash(getX(), getAlpha(), getY(), getZ(), getSnp(), getTgl(), getQ2Pt()); }
Expand Down
3 changes: 3 additions & 0 deletions DataFormats/Reconstruction/include/ReconstructionDataFormats/TrackParametrizationWithError.h
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Expand Up @@ -25,6 +25,8 @@ namespace o2
namespace track
{

class TrackParCovFwd; // fwd declaration for conversion method

template <typename value_T = float>
class TrackParametrizationWithError : public TrackParametrization<value_T>
{ // track+error parameterization
Expand Down Expand Up @@ -82,6 +84,7 @@ class TrackParametrizationWithError : public TrackParametrization<value_T>
GPUd() void print() const;
GPUd() void printHexadecimal();
#ifndef GPUCA_ALIGPUCODE
bool toFwdTrackParCov(TrackParCovFwd& t) const;
std::string asString() const;
std::string asStringHexadecimal();
#endif
Expand Down
78 changes: 77 additions & 1 deletion DataFormats/Reconstruction/src/TrackFwd.cxx
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Expand Up @@ -10,6 +10,8 @@
// or submit itself to any jurisdiction.

#include "ReconstructionDataFormats/TrackFwd.h"
#include "ReconstructionDataFormats/TrackParametrization.h"
#include "ReconstructionDataFormats/TrackParametrizationWithError.h"
#include "Math/MatrixFunctions.h"
#include <GPUCommonLogger.h>

Expand Down Expand Up @@ -41,7 +43,7 @@ void TrackParFwd::propagateParamToZlinear(double zEnd)
auto dZ = (zEnd - getZ());
auto phi0 = getPhi();
auto [sinphi0, cosphi0] = o2::math_utils::sincosd(phi0);
auto invtanl0 = 1.0 / getTanl();
auto invtanl0 = 1.0 / getTgl();
auto n = dZ * invtanl0;
mParameters(0) += n * cosphi0;
mParameters(1) += n * sinphi0;
Expand Down Expand Up @@ -572,5 +574,79 @@ void TrackParCovFwd::propagateToDCAhelix(double zField, const std::array<double,
return;
}

template <typename T>
void TrackParFwd::toBarrelTrackPar(TrackParametrization<T>& t) const
{
// we select the barrel frame with alpha = phi, then by construction the snp is 0
auto alpha = getPhi();
auto csa = TMath::Cos(alpha), sna = TMath::Sin(alpha);
t.setAlpha(alpha);
t.setX(csa * getX() + sna * getY());
t.setY(-sna * getX() + csa * getY());
t.setZ(getZ());
t.setSnp(0);
t.setTgl(getTanl());
t.setQ2Pt(getInvQPt());
}

template <typename T>
void TrackParCovFwd::toBarrelTrackParCov(TrackParametrizationWithError<T>& t) const
{
// We select the barrel frame with alpha = phi, then by construction the snp is 0
auto alpha = getPhi();
auto csa = TMath::Cos(alpha), sna = TMath::Sin(alpha);
t.setAlpha(alpha);
t.setX(csa * getX() + sna * getY());
t.setY(-sna * getX() + csa * getY());
t.setZ(getZ());
t.setSnp(0);
t.setTgl(getTgl());
t.setQ2Pt(getInvQPt());
/*
The standard Jacobian d{barrel_param} / d{fwd_param} should be augmented by the "forward" uncertainty
in X_barrel translated to uncertainty in Z, i.e:
A fwd param variation delta_x, delta_y leads to barrel frame coordinate variaion
delta_xb = csa delta_x + sna delta_y
delta_yb = -sna delta_x + csa delta_y
with dx_b/dz = csp/tgL = 1/tgL, dy_b/dz = snp/tgL = 0 (for phi 0 in the tracking frame) the variation of delta_xb would require
a shift in delta_zb = -tgL delta_xb to stat at the same X.
So, for alpha=phi (-> snp=0) choice the full Jacobian fwd->barrel is:
/ -sna csa 0 0 0 \
| -tgL*csa -tgL*sna 0 0 0 |
| 0 0 1 0 0 |
| 0 0 0 1 0 |
\ 0 0 0 0 1 /
*/
const T a1 = -sna;
const T a2 = csa;
const T b1 = -getTgl() * csa;
const T b2 = -getTgl() * sna;
const T cphi = 1;
const auto& C = getCovariances();
typename TrackParametrizationWithError<T>::covMat_t covBarrel = {
T(a1 * a1 * C(0, 0) + 2 * a1 * a2 * C(0, 1) + a2 * a2 * C(1, 1)), // kSigY2
T(a1 * b1 * C(0, 0) + (a1 * b2 + a2 * b1) * C(0, 1) + a2 * b2 * C(1, 1)), // kSigZY
T(b1 * b1 * C(0, 0) + 2 * b1 * b2 * C(0, 1) + b2 * b2 * C(1, 1)), // kSigZ2
T(csa * (a1 * C(0, 2) + a2 * C(1, 2))), // kSigSnpY
T(csa * (b1 * C(0, 2) + b2 * C(1, 2))), // kSigSnpZ
T(csa * csa * C(2, 2)), // kSigSnp2
T(a1 * C(0, 3) + a2 * C(1, 3)), // kSigTglY
T(b1 * C(0, 3) + b2 * C(1, 3)), // kSigTglZ
T(csa * C(2, 3)), // kSigTglSnp
T(C(3, 3)), // kSigTgl2
T(a1 * C(0, 4) + a2 * C(1, 4)), // kSigQ2PtY
T(b1 * C(0, 4) + b2 * C(1, 4)), // kSigQ2PtZ
T(csa * C(2, 4)), // kSigQ2PtSnp
T(C(3, 4)), // kSigQ2PtTgl
T(C(4, 4)) // kSigQ2Pt2
};
t.setCov(covBarrel);
}

template void TrackParFwd::toBarrelTrackPar<float>(TrackParametrization<float>&) const;
template void TrackParFwd::toBarrelTrackPar<double>(TrackParametrization<double>&) const;
template void TrackParCovFwd::toBarrelTrackParCov<float>(TrackParametrizationWithError<float>&) const;
template void TrackParCovFwd::toBarrelTrackParCov<double>(TrackParametrizationWithError<double>&) const;

} // namespace track
} // namespace o2
16 changes: 16 additions & 0 deletions DataFormats/Reconstruction/src/TrackParametrization.cxx
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Expand Up @@ -26,6 +26,7 @@

#ifndef GPUCA_ALIGPUCODE
#include <fmt/printf.h>
#include "ReconstructionDataFormats/TrackFwd.h"
#endif

using namespace o2::gpu;
Expand Down Expand Up @@ -985,6 +986,21 @@ GPUd() typename TrackParametrization<value_T>::value_t TrackParametrization<valu
return ttmp.propagateParamToDCA({xmv, ymv, zmv}, b, &dca) ? dca[1] : -9999.;
}

#ifndef GPUCA_ALIGPUCODE
//______________________________________________
template <typename value_T>
void TrackParametrization<value_T>::toFwdTrackPar(TrackParFwd& t) const
{
auto p = getXYZGlo();
t.setZ(p.Z());
t.setX(p.X());
t.setY(p.Y());
t.setPhi(getPhi());
t.setTanl(getTgl());
t.setInvQPt(getQ2Pt());
}
#endif

namespace o2::track
{
#if !defined(GPUCA_GPUCODE) || defined(GPUCA_GPUCODE_DEVICE) // FIXME: DR: WORKAROUND to avoid CUDA bug creating host symbols for device code.
Expand Down
59 changes: 59 additions & 0 deletions DataFormats/Reconstruction/src/TrackParametrizationWithError.cxx
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Expand Up @@ -21,6 +21,7 @@

#ifndef GPUCA_ALIGPUCODE
#include <fmt/printf.h>
#include "ReconstructionDataFormats/TrackFwd.h"
#endif

using namespace o2::track;
Expand Down Expand Up @@ -1768,6 +1769,64 @@ GPUd() void TrackParametrizationWithError<value_T>::printHexadecimal()
#endif
}

#ifndef GPUCA_ALIGPUCODE
//______________________________________________________________
template <typename value_T>
bool TrackParametrizationWithError<value_T>::toFwdTrackParCov(TrackParCovFwd& t) const
{
auto p = this->getXYZGlo();
t.setZ(p.Z());
t.setX(p.X());
t.setY(p.Y());
t.setPhi(this->getPhi());
t.setTanl(this->getTgl());
t.setInvQPt(this->getQ2Pt());
//
if (gpu::CAMath::Abs(this->getSnp()) >= o2::constants::math::Almost1 ||
gpu::CAMath::Abs(this->getTgl()) <= o2::constants::math::Almost0) {
return false;
}
value_T csa, sna, csP, snP, csp = gpu::CAMath::Sqrt((1. - this->getSnp()) * (1. + this->getSnp()));
math_utils::detail::sincos(value_T(this->getAlpha()), sna, csa);
math_utils::detail::sincos(value_T(t.getPhi()), snP, csP);
/*
Jacobian is
/-sna -csP/tgL 0 0 0 \
| csa -snP/tgL 0 0 0 |
| 0 0 1/csp 0 0 |
| 0 0 0 1 0 |
\ 0 0 0 0 1 /
*/
auto tgLI = 1 / this->getTgl();
const value_T d1 = -sna;
const value_T d2 = -csP * tgLI;
const value_T e1 = csa;
const value_T e2 = -snP * tgLI;
const value_T f1 = 1 / csp;
SMatrix55Sym C;
C(0, 0) = d1 * d1 * getSigmaY2() + 2 * d1 * d2 * getSigmaZY() + d2 * d2 * getSigmaZ2();
C(0, 1) = d1 * e1 * getSigmaY2() + (d1 * e2 + d2 * e1) * getSigmaZY() + d2 * e2 * getSigmaZ2();
C(1, 1) = e1 * e1 * getSigmaY2() + 2 * e1 * e2 * getSigmaZY() + e2 * e2 * getSigmaZ2();

C(0, 2) = f1 * (d1 * getSigmaSnpY() + d2 * getSigmaSnpZ());
C(1, 2) = f1 * (e1 * getSigmaSnpY() + e2 * getSigmaSnpZ());
C(2, 2) = f1 * f1 * getSigmaSnp2();

C(0, 3) = d1 * getSigmaTglY() + d2 * getSigmaTglZ();
C(1, 3) = e1 * getSigmaTglY() + e2 * getSigmaTglZ();
C(2, 3) = f1 * getSigmaTglSnp();
C(3, 3) = getSigmaTgl2();

C(0, 4) = d1 * getSigma1PtY() + d2 * getSigma1PtZ();
C(1, 4) = e1 * getSigma1PtY() + e2 * getSigma1PtZ();
C(2, 4) = f1 * getSigma1PtSnp();
C(3, 4) = getSigma1PtTgl();
C(4, 4) = getSigma1Pt2();
t.setCovariances(C);
return true;
}
#endif

namespace o2::track
{
#if !defined(GPUCA_GPUCODE) || defined(GPUCA_GPUCODE_DEVICE) // FIXME: DR: WORKAROUND to avoid CUDA bug creating host symbols for device code.
Expand Down
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