PLMD::SwitchingFunction Class Reference

Small class to compure switching functions. More...

#include <SwitchingFunction.h>

Public Member Functions
	SwitchingFunction ()
	Constructor. More...
	~SwitchingFunction ()
	Destructor. More...
	SwitchingFunction (const SwitchingFunction &)
	Copy constructor. More...
SwitchingFunction &	operator= (const SwitchingFunction &)
	Assignment operator. More...
void	set (int nn, int mm, double r_0, double d_0)
	Set a "rational" switching function. More...
void	set (const std::string &definition, std::string &errormsg)
	Set an arbitrary switching function. More...
std::string	description () const
	Returns a string with a description of the switching function. More...
double	calculate (double x, double &df) const
	Compute the switching function. More...
double	calculateSqr (double distance2, double &dfunc) const
	Compute the switching function. More...
double	get_d0 () const
	Returns d0. More...
double	get_r0 () const
	Returns r0. More...
double	get_dmax () const
	Return dmax. More...
double	get_dmax2 () const
	Return dmax squared. More...

Static Public Member Functions
static void	registerKeywords (Keywords &keys)

Private Types
enum	{   rational, exponential, gaussian, smap,   cubic, tanh, matheval, nativeq }
	Type of function. More...

Private Member Functions
double	do_rational (double rdist, double &dfunc, int nn, int mm) const
	Low-level tool to compute rational functions. More...

Private Attributes
bool	init
	This is to check that switching function has been initialized. More...
enum PLMD::SwitchingFunction:: { ... }	type
	Type of function. More...
double	invr0
	Inverse of scaling length. More...
double	d0
	Minimum distance (before this, function is one) More...
double	dmax
	Maximum distance (after this, function is zero) More...
int	nn
	Exponents for rational function. More...
int	mm
int	a
	Parameters for smap function. More...
int	b
double	c
double	d
double	lambda
double	beta
double	ref
double	invr0_2
	Square of invr0, useful in calculateSqr() More...
double	dmax_2
	Square of dmax, useful in calculateSqr() More...
double	stretch
	Parameters for stretching the function to zero at d_max. More...
double	shift
std::vector< void * >	evaluator
	Evaluator for matheval: More...
std::vector< void * >	evaluator_deriv
	Evaluator for matheval: More...

Detailed Description

Small class to compure switching functions.

Switching functions are created using set() and then can be used with function calculate() or calculateSqr(). Since this is typically computed on a distance vector, the second all (calculateSqr()) allows to skip the calculation of a square root in some case, thus potentially increasing performances.

Member Enumeration Documentation

anonymous enum

anonymous enum

private

Type of function.

Enumerator
rational
exponential
gaussian
smap
cubic
tanh
matheval
nativeq

Constructor & Destructor Documentation

SwitchingFunction() [1/2]

PLMD::SwitchingFunction::SwitchingFunction

(

)

Constructor.

~SwitchingFunction()

PLMD::SwitchingFunction::~SwitchingFunction

(

)

Destructor.

SwitchingFunction() [2/2]

PLMD::SwitchingFunction::SwitchingFunction

(

const SwitchingFunction &

sf

)

Copy constructor.

Member Function Documentation

calculate()

double PLMD::SwitchingFunction::calculate	(	double	x,
		double &	df
	)		const

Compute the switching function.

Returns s(x). df will be set to the value of the derivative of the switching function _divided_by_x

calculateSqr()

double PLMD::SwitchingFunction::calculateSqr	(	double	distance2,
		double &	dfunc
	)		const

Compute the switching function.

Returns \( s(\sqrt{x})\) . df will be set to the \( \frac{1}{\sqrt{x}}\frac{ds}{d\sqrt{x}}= 2 \frac{ds}{dx}\) (same as calculate()). The advantage is that in some case the expensive square root can be avoided (namely for rational functions, if nn and mm are even and d0 is zero)

description()

std::string PLMD::SwitchingFunction::description

(

)

const

Returns a string with a description of the switching function.

do_rational()

double PLMD::SwitchingFunction::do_rational ( double  rdist, double &  dfunc, int  nn, int  mm  ) const

private

Low-level tool to compute rational functions.

It is separated since it is called both by calculate() and calculateSqr()

get_d0()

double PLMD::SwitchingFunction::get_d0

(

)

const

Returns d0.

get_dmax()

double PLMD::SwitchingFunction::get_dmax

(

)

const

Return dmax.

get_dmax2()

double PLMD::SwitchingFunction::get_dmax2

(

)

const

Return dmax squared.

get_r0()

double PLMD::SwitchingFunction::get_r0

(

)

const

Returns r0.

operator=()

SwitchingFunction & PLMD::SwitchingFunction::operator=

(

const SwitchingFunction &

sf

)

Assignment operator.

registerKeywords()

void PLMD::SwitchingFunction::registerKeywords ( Keywords &  keys )

static

set() [1/2]

void PLMD::SwitchingFunction::set	(	int	nn,
		int	mm,
		double	r_0,
		double	d_0
	)

Set a "rational" switching function.

Notice that a d_max is set automatically to a value such that f(d_max)=0.00001.

set() [2/2]

void PLMD::SwitchingFunction::set	(	const std::string &	definition,
		std::string &	errormsg
	)

Set an arbitrary switching function.

Parse the string in definition and possibly returns errors in the errormsg string

Member Data Documentation

a

int PLMD::SwitchingFunction::a

private

Parameters for smap function.

b

int PLMD::SwitchingFunction::b

private

beta

double PLMD::SwitchingFunction::beta

private

c

double PLMD::SwitchingFunction::c

private

d

double PLMD::SwitchingFunction::d

private

d0

double PLMD::SwitchingFunction::d0

private

Minimum distance (before this, function is one)

dmax

double PLMD::SwitchingFunction::dmax

private

Maximum distance (after this, function is zero)

dmax_2

double PLMD::SwitchingFunction::dmax_2

private

Square of dmax, useful in calculateSqr()

evaluator

std::vector<void*> PLMD::SwitchingFunction::evaluator

private

Evaluator for matheval:

Warning

Since evaluator is not thread safe, we should create one evaluator per thread.

evaluator_deriv

std::vector<void*> PLMD::SwitchingFunction::evaluator_deriv

private

Evaluator for matheval:

Warning

Since evaluator is not thread safe, we should create one evaluator per thread.

init

bool PLMD::SwitchingFunction::init

private

This is to check that switching function has been initialized.

invr0

double PLMD::SwitchingFunction::invr0

private

Inverse of scaling length.

We store the inverse to avoid a division

invr0_2

double PLMD::SwitchingFunction::invr0_2

private

Square of invr0, useful in calculateSqr()

lambda

double PLMD::SwitchingFunction::lambda

private

mm

int PLMD::SwitchingFunction::mm

private

nn

int PLMD::SwitchingFunction::nn

private

Exponents for rational function.

ref

double PLMD::SwitchingFunction::ref

private

shift

double PLMD::SwitchingFunction::shift

private

stretch

double PLMD::SwitchingFunction::stretch

private

Parameters for stretching the function to zero at d_max.

type

enum { ... } PLMD::SwitchingFunction::type

Type of function.

---

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

• tools/SwitchingFunction.h
• tools/SwitchingFunction.cpp