dnf_composer::element::AbsSigmoidFunction Struct Reference

Rational (absolute-value) sigmoid — cedar's default activation function. More...

#include <activation_function.h>

Inheritance diagram for dnf_composer::element::AbsSigmoidFunction:

Collaboration diagram for dnf_composer::element::AbsSigmoidFunction:

Public Member Functions
	AbsSigmoidFunction (const AbsSigmoidFunction &)=default
	AbsSigmoidFunction (double x_shift, double beta)
	Construct an AbsSigmoid with the given threshold and steepness.
void	apply (const std::vector< double > &input, std::vector< double > &out) const override
	Apply the activation function in-place into a pre-allocated out buffer. out must already be sized to input.size(). No heap allocation occurs.
std::unique_ptr< ActivationFunction >	clone () const override
double	getBeta () const
double	getXShift () const
std::vector< double >	operator() (const std::vector< double > &input) override
	Apply the activation function to input and return the result.
bool	operator== (const AbsSigmoidFunction &other) const
void	print () const override
std::string	toString () const override
	~AbsSigmoidFunction () override=default
Public Member Functions inherited from dnf_composer::element::ActivationFunction
	ActivationFunction ()=default
	ActivationFunction (const ActivationFunction &)=default
ActivationFunction &	operator= (const ActivationFunction &)=delete
virtual	~ActivationFunction ()=default

Public Attributes
double	beta
	Steepness parameter — cedar/cosivina naming (larger = steeper).
double	x_shift
	Inflection point / threshold (cedar: theta).
Public Attributes inherited from dnf_composer::element::ActivationFunction
ActivationFunctionType	type
	Concrete function type.

Detailed Description

Rational (absolute-value) sigmoid — cedar's default activation function.

Formula:

This is computationally cheaper than SigmoidFunction because it avoids std::exp. At the two functions are numerically indistinguishable (max pointwise error < 0.001).

Cross-framework equivalence:

Framework	Type / call	Exact?
dnf-composer	AbsSigmoidFunction(x_shift, beta)	✓
cedar	AbsSigmoid(beta=beta, theta=x_shift)	✓
cosivina	no built-in equivalent	—

Approximate equivalence to ExpSigmoid: Use SigmoidFunction(x_shift, beta) or cosivina sigmoid(beta=beta, x0=x_shift) — identical for .

Note

Cedar uses AbsSigmoid with by default (near-Heaviside). Published cedar parameter sets assume this steep nonlinearity.

Constructor & Destructor Documentation

AbsSigmoidFunction() [1/2]

dnf_composer::element::AbsSigmoidFunction::AbsSigmoidFunction ( const AbsSigmoidFunction &  )

default

AbsSigmoidFunction() [2/2]

dnf_composer::element::AbsSigmoidFunction::AbsSigmoidFunction	(	double	x_shift,
		double	beta
	)

Construct an AbsSigmoid with the given threshold and steepness.

Parameters

x_shift	Inflection point of the sigmoid.
beta	Slope parameter.

~AbsSigmoidFunction()

dnf_composer::element::AbsSigmoidFunction::~AbsSigmoidFunction ( )

overridedefault

Member Function Documentation

apply()

void dnf_composer::element::AbsSigmoidFunction::apply ( const std::vector< double > &  input, std::vector< double > &  out  ) const

overridevirtual

Apply the activation function in-place into a pre-allocated out buffer. out must already be sized to input.size(). No heap allocation occurs.

Implements dnf_composer::element::ActivationFunction.

clone()

std::unique_ptr< ActivationFunction > dnf_composer::element::AbsSigmoidFunction::clone ( ) const

overridevirtual

Implements dnf_composer::element::ActivationFunction.

getBeta()

double dnf_composer::element::AbsSigmoidFunction::getBeta

(

)

const

getXShift()

double dnf_composer::element::AbsSigmoidFunction::getXShift

(

)

const

operator()()

std::vector< double > dnf_composer::element::AbsSigmoidFunction::operator() ( const std::vector< double > &  input )

overridevirtual

Apply the activation function to input and return the result.

Implements dnf_composer::element::ActivationFunction.

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operator==()

bool dnf_composer::element::AbsSigmoidFunction::operator==

(

const AbsSigmoidFunction &

other

)

const

print()

void dnf_composer::element::AbsSigmoidFunction::print ( ) const

overridevirtual

Implements dnf_composer::element::ActivationFunction.

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toString()

std::string dnf_composer::element::AbsSigmoidFunction::toString ( ) const

overridevirtual

Implements dnf_composer::element::ActivationFunction.

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Member Data Documentation

beta

double dnf_composer::element::AbsSigmoidFunction::beta

Steepness parameter — cedar/cosivina naming (larger = steeper).

x_shift

double dnf_composer::element::AbsSigmoidFunction::x_shift

Inflection point / threshold (cedar: theta).

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The documentation for this struct was generated from the following files:

• include/elements/activation_function.h
• src/elements/activation_function.cpp