Class Acts::GaussianTrackDensity¶
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template<typename input_track_t>
class Acts::GaussianTrackDensity¶ Class to model tracks as 2D density functions based on their d0 and z0 perigee parameters (mean value) and covariance matrices (determining the width of the function)
Public Functions
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GaussianTrackDensity() = default¶
Default constructor.
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double globalMaximum(State &state, const std::vector<const input_track_t*> &trackList, const std::function<BoundTrackParameters(input_track_t)> &extractParameters) const¶
Calculates the z position of the global maximum.
- Parameters
state – The track density state
trackList – All input tracks
extractParameters – Function extracting BoundTrackParameters from InputTrack
- Returns
z position of the global maximum
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std::pair<double, double> globalMaximumWithWidth(State &state, const std::vector<const input_track_t*> &trackList, const std::function<BoundTrackParameters(input_track_t)> &extractParameters) const¶
Calculates z position of global maximum with Gaussian width for density function.
Strategy: The global maximum must be somewhere near a track. Since we can calculate the first and second derivatives, at each point we can determine a) whether the function is curved up (minimum) or down (maximum) b) the distance to nearest maximum, assuming either Newton (parabolic) or Gaussian local behavior. For each track where the second derivative is negative, find step to nearest maximum, take that step and then do one final refinement. The largest density encountered in this procedure (after checking all tracks) is considered the maximum.
- Parameters
state – The track density state
trackList – All input tracks
extractParameters – Function extracting BoundTrackParameters from InputTrack
- Returns
Pair of position of global maximum and Gaussian width
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struct Config¶
The Config struct.
Public Functions
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inline Config(double d0Sig = 3.5, double z0Sig = 12.)¶
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inline Config(double d0Sig = 3.5, double z0Sig = 12.)¶
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struct State¶
The State struct.
Public Functions
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inline State(unsigned int nTracks)¶
Public Members
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std::vector<TrackEntry> trackEntries¶
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inline State(unsigned int nTracks)¶
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struct TrackEntry¶
Struct to store information for a single track.
Public Functions
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TrackEntry() = default¶
Default constructor.
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inline TrackEntry(double z_, double c0_, double c1_, double c2_, double lowerBound_, double upperBound_)¶
Constructor initializing all members.
- Parameters
z_ – Trial z position
c0_ – z-independent term in exponent
c1_ – Linear coefficient in exponent
c2_ – Quadratic coefficient in exponent
lowerBound_ – The lower bound
upperBound_ – The upper bound
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TrackEntry() = default¶
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GaussianTrackDensity() = default¶