LookupTable< T > Class Template Reference

Class which holds precomputed values of a function. More...

#include <LookupTable.h>

Collaboration diagram for LookupTable< T >:

Public Member Functions
	LookupTable (const std::function< T(double)> &map, std::size_t nBins, double lowerBound, double upperBound)
	Constructs a look up table for the given function The function is sampled at nBins + 1 equally spaced points between the given bounds, such that the distance between consecutive sampling points is (upperBound - lowerBound) / nBins.
T	operator() (double x) const
	Evaluate as piecewise linear interpolation.
const T &	nearest (double x) const
	Return the precomputed value at the position closest to the given value.
const T &	at (int i) const
	Return the value at the given index.
int	getNBins () const
	Return the number of bins in this lookup table.
int	getNPoints () const
	Return the number of finite sampling points in this lookup table.

Private Attributes
double	m_lowerBound
	Lower bound of the precomputed range.
double	m_upperBound
	Upper bound of the precomputed range.
double	m_binWidth
	Distance between two precomputed positions.
std::vector< T >	m_values
	Precomputed value.

Detailed Description

template<class T = double>
class Belle2::TrackFindingCDC::LookupTable< T >

Class which holds precomputed values of a function.

Definition at line 50 of file LookupTable.h.

Constructor & Destructor Documentation

LookupTable()

LookupTable ( const std::function< T(double)> &  map, std::size_t  nBins, double  lowerBound, double  upperBound  )

inline

Constructs a look up table for the given function The function is sampled at nBins + 1 equally spaced points between the given bounds, such that the distance between consecutive sampling points is (upperBound - lowerBound) / nBins.

Definition at line 59 of file LookupTable.h.

        : m_lowerBound(lowerBound)
        , m_upperBound(upperBound)
        , m_binWidth((m_upperBound - m_lowerBound) / nBins)
        , m_values(linspace(lowerBound, upperBound, nBins + 1, map))
      {
        // Add a sentinel at the back.
        m_values.push_back(map(NAN));
      }

Member Function Documentation

at()

const T & at ( int  i ) const

inline

Return the value at the given index.

Definition at line 94 of file LookupTable.h.

      {
        const int iMax =  m_values.size() - 2; // Subtracting sentinel index
        i = std::min(std::max(0, i), iMax);
        return m_values[i];
      }

getNBins()

int getNBins ( ) const

inline

Return the number of bins in this lookup table.

Definition at line 102 of file LookupTable.h.

      {
        return m_values.size() - 2;
      }

getNPoints()

int getNPoints ( ) const

inline

Return the number of finite sampling points in this lookup table.

Definition at line 108 of file LookupTable.h.

      {
        return m_values.size() - 1;
      }

nearest()

const T & nearest ( double  x ) const

inline

Return the precomputed value at the position closest to the given value.

Definition at line 84 of file LookupTable.h.

      {
        if (not std::isfinite(x)) return m_values.back(); // Return sentinel value
        const int iMax =  m_values.size() - 2; // Subtracting sentinel index
        int iBin = std::round((x - m_lowerBound) / m_binWidth);
        int i = std::min(std::max(0, iBin), iMax);
        return m_values[i];
      }

operator()()

T operator() ( double  x ) const

inline

Evaluate as piecewise linear interpolation.

Definition at line 73 of file LookupTable.h.

      {
        if (not std::isfinite(x)) return m_values.back(); // Return sentinel
        const int iMax =  m_values.size() - 2; // Subtracting sentinel index
        double iBin = 0;
        double delta = std::modf((x - m_lowerBound) / m_binWidth, &iBin);
        int i = std::min(std::max(0, static_cast<int>(iBin)), iMax);
        return m_values[i] * (1 - delta) + m_values[i + 1] * delta;
      }

Member Data Documentation

m_binWidth

double m_binWidth

private

Distance between two precomputed positions.

Definition at line 121 of file LookupTable.h.

m_lowerBound

double m_lowerBound

private

Lower bound of the precomputed range.

Definition at line 115 of file LookupTable.h.

m_upperBound

double m_upperBound

private

Upper bound of the precomputed range.

Definition at line 118 of file LookupTable.h.

m_values

std::vector<T> m_values

private

Precomputed value.

Definition at line 124 of file LookupTable.h.

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The documentation for this class was generated from the following file:

• tracking/trackFindingCDC/numerics/include/LookupTable.h