File Measurement.hpp¶
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namespace Acts
Note
This file is foreseen for the
Geometry
module to replaceExtent
Typedefs
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using BoundVariantMeasurement = VariantMeasurement<BoundIndices>¶
Variant that can hold all possible bound measurements.
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using FreeVariantMeasurement = VariantMeasurement<FreeIndices>¶
Variant that can hold all possible free measurements.
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using VariantMeasurement = typename detail::VariantMeasurementGenerator<indices_t, detail::kParametersSize<indices_t>>::Type¶
Variant that can contain all possible measurements in a parameter space.
- Template Parameters
indices_t – Parameter index type, determines the full parameter space
Functions
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template<typename parameters_t, typename covariance_t, typename indices_t, typename ...tail_indices_t>
auto makeMeasurement(SourceLink source, const Eigen::MatrixBase<parameters_t> ¶ms, const Eigen::MatrixBase<covariance_t> &cov, indices_t index0, tail_indices_t... tailIndices) -> Measurement<indices_t, 1u + sizeof...(tail_indices_t)>¶ Construct a fixed-size measurement for the given indices.
This helper function can be used to create a fixed-size measurement using an explicit set of indices, e.g.
auto m = makeMeasurement(s, p, c, eBoundLoc0, eBoundTime);
for a 2d measurement w/ one position and time.
Note
The indices must be ordered and must be consistent with the content of parameters and covariance.
- Template Parameters
parameters_t – Input parameters vector type
covariance_t – Input covariance matrix type
indices_t – Parameter index type, determines the full parameter space
tail_indices_t – Helper types required to support variadic arguments; all types must be convertibale to
indices_t
.
- Parameters
source – The link that connects to the underlying detector readout
params – Measured parameters values
cov – Measured parameters covariance
index0 – Required parameter index, measurement must be at least 1d
tailIndices – Additional parameter indices for larger measurements
- Returns
Fixed-size measurement w/ the correct type and given inputs
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template<typename indices_t>
std::ostream &operator<<(std::ostream &os, const VariantMeasurement<indices_t> &vm)¶
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template<typename indices_t, size_t kSize>
class Measurement - #include <Acts/EventData/Measurement.hpp>
A measurement of a fixed-size subspace of the full parameters.
The measurement intentionally does not store a pointer/reference to the reference object in the geometry hierarchy, i.e. the surface or volume. The reference object can already be identified via the geometry identifier provided by the source link. Since a measurement must be anchored within the geometry hierarchy, all measurement surfaces and volumes must provide valid geometry identifiers. In all use-cases, e.g. Kalman filtering, a pointer/reference to the reference object is available before the measurement is accessed; e.g. the propagator provides the surface pointer during navigation, which is then used to lookup possible measurements.
The pointed-to geometry object would differ depending on the parameter type. This means either, that there needs to be an additional variable type or that a pointer to a base object is stored (requiring a
dynamic_cast
later on). Both variants add additional complications. Since the geometry object is not required anyways (as discussed above), not storing it removes all these complications altogether.- Template Parameters
indices_t – Parameter index type, determines the full parameter space
kSize – Size of the parameter subset.
Public Types
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using CovarianceMatrix = ActsSymMatrix<kSize>
Matrix type for the measurement covariance.
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using ExpansionMatrix = ActsMatrix<kFullSize, kSize>
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using FullParametersVector = ActsVector<kFullSize>
Vector type containing all parameters in the same space.
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using ParametersVector = ActsVector<kSize>
Vector type containing for measured parameter values.
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using ProjectionMatrix = ActsMatrix<kSize, kFullSize>
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using Scalar = ActsScalar
Public Functions
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template<typename parameters_t, typename covariance_t>
inline Measurement(SourceLink source, const std::array<indices_t, kSize> &indices, const Eigen::MatrixBase<parameters_t> ¶ms, const Eigen::MatrixBase<covariance_t> &cov) Construct from source link, subset indices, and measured data.
Note
The indices must be ordered and must describe/match the content of parameters and covariance.
- Template Parameters
parameters_t – Input parameters vector type
covariance_t – Input covariance matrix type
- Parameters
source – The link that connects to the underlying detector readout
indices – Which parameters are measured
params – Measured parameters values
cov – Measured parameters covariance
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Measurement() = delete
A measurement can only be constructed with valid parameters.
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Measurement(const Measurement&) = default
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Measurement(Measurement&&) = default
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~Measurement() = default
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inline bool contains(indices_t i) const
Check if a specific parameter is part of this measurement.
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inline const CovarianceMatrix &covariance() const
Measured parameters covariance.
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inline ExpansionMatrix expander() const
Expansion matrix from the measured subspace into the full space.
This is equivalent to the tranpose of the projection matrix only in the case of a trivial projection matrix. While this is the case here, it is still recommended to use the expansion matrix directly in cases where it is explicitely used.
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inline std::ostream &operator<<(std::ostream &os) const
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Measurement &operator=(const Measurement&) = default
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Measurement &operator=(Measurement&&) = default
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inline const ParametersVector ¶meters() const
Measured parameters values.
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inline ProjectionMatrix projector() const
Projection matrix from the full space into the measured subspace.
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inline ParametersVector residuals(const FullParametersVector &reference) const
Compute residuals in the measured subspace.
This computes the difference
measured - reference
taking into account the allowed parameter ranges. Only the reference values in the measured subspace are used for the computation.- Parameters
reference – Reference parameters in the full space.
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inline const SourceLink &sourceLink() const
Source link that connects to the underlying detector readout.
Public Static Functions
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static inline constexpr size_t size()
Number of measured parameters.
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using BoundVariantMeasurement = VariantMeasurement<BoundIndices>¶