Class for approximating expensive arithmetic operations. More...

#include <juce_LookupTable.h>

Inheritance diagram for juce::dsp::LookupTableTransform< FloatType >:

Collaboration diagram for juce::dsp::LookupTableTransform< FloatType >:

Public Member Functions
	LookupTableTransform ()=default
	Creates an uninitialised LookupTableTransform object. More...

	LookupTableTransform (const std::function< FloatType(FloatType)> &functionToApproximate, FloatType minInputValueToUse, FloatType maxInputValueToUse, size_t numPoints)
	Creates and initialises a LookupTableTransform object. More...

void	initialise (const std::function< FloatType(FloatType)> &functionToApproximate, FloatType minInputValueToUse, FloatType maxInputValueToUse, size_t numPoints)
	Initialises or changes the parameters of a LookupTableTransform object. More...

FloatType	operator() (FloatType index) const noexcept

FloatType	operator[] (FloatType index) const noexcept

void	process (const FloatType input, FloatType output, size_t numSamples) const noexcept
	Processes an array of input values with range checking. More...

FloatType	processSample (FloatType value) const noexcept
	Calculates the approximated value for the given input value with range checking. More...

FloatType	processSampleUnchecked (FloatType value) const noexcept
	Calculates the approximated value for the given input value without range checking. More...

void	processUnchecked (const FloatType input, FloatType output, size_t numSamples) const noexcept
	Processes an array of input values without range checking. More...

Static Public Member Functions
static double	calculateMaxRelativeError (const std::function< FloatType(FloatType)> &functionToApproximate, FloatType minInputValue, FloatType maxInputValue, size_t numPoints, size_t numTestPoints=0)
	Calculates the maximum relative error of the approximation for the specified parameter set. More...

Static Private Member Functions
static double	calculateRelativeDifference (double, double) noexcept

Private Attributes
LookupTable< FloatType >	lookupTable

FloatType	maxInputValue

FloatType	minInputValue

FloatType	offset

FloatType	scaler

Detailed Description

template<typename FloatType>
class juce::dsp::LookupTableTransform< FloatType >

Class for approximating expensive arithmetic operations.

Once initialised, this class can be used just like the function it approximates via operator().

Example:

LookupTableTransform<float> tanhApprox ([] (float x) { return std::tanh (x); }, -5.0f, 5.0f, 64);
auto outValue = tanhApprox (4.2f);

Note: If you try to call the function with an input outside the provided range, it will return either the first or the last recorded LookupTable value.

See also: LookupTable

@tags{DSP}

Constructor & Destructor Documentation

◆ LookupTableTransform() [1/2]

template<typename FloatType >

juce::dsp::LookupTableTransform< FloatType >::LookupTableTransform ( )

default

Creates an uninitialised LookupTableTransform object.

You need to call initialise() before using the object. Prefer using the non-default constructor instead.

See also: initialise

◆ LookupTableTransform() [2/2]

template<typename FloatType >

juce::dsp::LookupTableTransform< FloatType >::LookupTableTransform	(	const std::function< FloatType(FloatType)> &	functionToApproximate,
		FloatType	minInputValueToUse,
		FloatType	maxInputValueToUse,
		size_t	numPoints
	)

inline

Creates and initialises a LookupTableTransform object.

Parameters

functionToApproximate	The function to be approximated. This should be a mapping from a FloatType to FloatType.
minInputValueToUse	The lowest input value used. The approximation will fail for values lower than this.
maxInputValueToUse	The highest input value used. The approximation will fail for values higher than this.
numPoints	The number of pre-calculated values stored.

Member Function Documentation

◆ calculateMaxRelativeError()

template<typename FloatType >

static double juce::dsp::LookupTableTransform< FloatType >::calculateMaxRelativeError	(	const std::function< FloatType(FloatType)> &	functionToApproximate,
		FloatType	minInputValue,
		FloatType	maxInputValue,
		size_t	numPoints,
		size_t	numTestPoints = `0`
	)

static

Calculates the maximum relative error of the approximation for the specified parameter set.

The closer the returned value is to zero the more accurate the approximation is.

This function compares the approximated output of this class to the function it approximates at a range of points and returns the maximum relative error. This can be used to determine if the approximation is suitable for the given problem. The accuracy of the approximation can generally be improved by increasing numPoints.

Parameters

functionToApproximate	The approximated function. This should be a mapping from a FloatType to FloatType.
minInputValue	The lowest input value used.
maxInputValue	The highest input value used.
numPoints	The number of pre-calculated values stored.
numTestPoints	The number of input values used for error calculation. Higher numbers can increase the accuracy of the error calculation. If it's zero then 100 * numPoints will be used.

◆ calculateRelativeDifference()

template<typename FloatType >

static double juce::dsp::LookupTableTransform< FloatType >::calculateRelativeDifference	(	double	,
		double
	)

staticprivatenoexcept

◆ initialise()

template<typename FloatType >

void juce::dsp::LookupTableTransform< FloatType >::initialise	(	const std::function< FloatType(FloatType)> &	functionToApproximate,
		FloatType	minInputValueToUse,
		FloatType	maxInputValueToUse,
		size_t	numPoints
	)

Initialises or changes the parameters of a LookupTableTransform object.

Parameters

functionToApproximate	The function to be approximated. This should be a mapping from a FloatType to FloatType.
minInputValueToUse	The lowest input value used. The approximation will fail for values lower than this.
maxInputValueToUse	The highest input value used. The approximation will fail for values higher than this.
numPoints	The number of pre-calculated values stored.

Referenced by juce::dsp::LookupTableTransform< NumericType >::LookupTableTransform().

◆ operator()()

template<typename FloatType >

FloatType juce::dsp::LookupTableTransform< FloatType >::operator() ( FloatType index ) const

inlinenoexcept

See also: processSample

◆ operator[]()

template<typename FloatType >

FloatType juce::dsp::LookupTableTransform< FloatType >::operator[] ( FloatType index ) const

inlinenoexcept

See also: processSampleUnchecked

◆ process()

template<typename FloatType >

void juce::dsp::LookupTableTransform< FloatType >::process	(	const FloatType *	input,
		FloatType *	output,
		size_t	numSamples
	)		const

inlinenoexcept

Processes an array of input values with range checking.

See also: processUnchecked

◆ processSample()

template<typename FloatType >

FloatType juce::dsp::LookupTableTransform< FloatType >::processSample ( FloatType value ) const

inlinenoexcept

Calculates the approximated value for the given input value with range checking.

This can be called with any input values. Out-of-range input values will be clipped to the specified input range.

If the index is guaranteed to be in range use the faster processSampleUnchecked() instead.

Parameters

value The approximation is calculated for this input value.

Returns: The approximated value for the provided input value.

See also: processSampleUnchecked, operator(), operator[]

Referenced by juce::dsp::LookupTableTransform< NumericType >::operator()(), and juce::dsp::LookupTableTransform< NumericType >::process().

◆ processSampleUnchecked()

template<typename FloatType >

FloatType juce::dsp::LookupTableTransform< FloatType >::processSampleUnchecked ( FloatType value ) const

inlinenoexcept

Calculates the approximated value for the given input value without range checking.

Use this if you can guarantee that the input value is within the range specified in the constructor or initialise(), otherwise use processSample().

Parameters

value The approximation is calculated for this input value.

Returns: The approximated value for the provided input value.

See also: processSample, operator(), operator[]

Referenced by juce::dsp::LookupTableTransform< NumericType >::operator[](), and juce::dsp::LookupTableTransform< NumericType >::processUnchecked().

◆ processUnchecked()

template<typename FloatType >

void juce::dsp::LookupTableTransform< FloatType >::processUnchecked	(	const FloatType *	input,
		FloatType *	output,
		size_t	numSamples
	)		const

inlinenoexcept

Processes an array of input values without range checking.

See also: process

Referenced by juce::dsp::LookupTableTransform< NumericType >::processSample(), and juce::dsp::LookupTableTransform< NumericType >::processSampleUnchecked().

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

juce_LookupTable.h

Public Member Functions

Static Public Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

template<typename FloatType> class juce::dsp::LookupTableTransform< FloatType >

Constructor & Destructor Documentation

◆ LookupTableTransform() [1/2]

◆ LookupTableTransform() [2/2]

Member Function Documentation

◆ calculateMaxRelativeError()

◆ calculateRelativeDifference()

◆ initialise()

◆ operator()()

◆ operator[]()

◆ process()

◆ processSample()

◆ processSampleUnchecked()

◆ processUnchecked()

Member Data Documentation

◆ lookupTable

◆ maxInputValue

◆ minInputValue

◆ offset

◆ scaler

template<typename FloatType>
class juce::dsp::LookupTableTransform< FloatType >