BoysFunction Class Reference

Calculates the Boys function efficiently for any argument and level. More...

#include <boysfunction.h>

Collaboration diagram for BoysFunction:

Public Member Functions
	BoysFunction ()
	BoysFunction (double arg, int levelMax=0, BoysFunctionIntermediate *intermediate=0)
void	set (double arg, int levelMax=0, BoysFunctionIntermediate *intermediate=0)
double	result (int level=0) const

Static Public Member Functions
static double	calculateAsymptopticForm (double arg, int level)
static double	calculateTaylorExpansion (double arg, int level)
static double	calculateZeroLevel (double arg)
static double	doubleFactorial (double n)
static double	factorial (double n)

Protected Attributes
vec	m_results
BoysFunctionIntermediate *	m_intermediate

Detailed Description

Calculates the Boys function efficiently for any argument and level.

The argument and the highest level is specified upon construction, while the other levels are fetched on demand.

Definition at line 10 of file boysfunction.h.

Constructor & Destructor Documentation

BoysFunction::BoysFunction

(

)

Definition at line 15 of file boysfunction.cpp.

{

}

BoysFunction::BoysFunction	(	double	arg,
		int	levelMax = 0,
		BoysFunctionIntermediate *	intermediate = 0
	)

Definition at line 20 of file boysfunction.cpp.

{
    set(arg, levelMax, intermediate);
}

Member Function Documentation

double BoysFunction::calculateAsymptopticForm ( double  arg, int  level  )

static

Definition at line 56 of file boysfunction.cpp.

                                                                   {
    double n = level;
    double dfac = doubleFactorial(2 * n - 1);
    double result = dfac / pow(2, n + 1) * sqrt(M_PI / pow(arg, 2*n + 1));
    return result;
}

double BoysFunction::calculateTaylorExpansion ( double  arg, int  level  )

static

Definition at line 86 of file boysfunction.cpp.

                                                                   {
    double n = level;
    double result = 0;
    for(int k = 0; k < 100; k++) {
        result += pow(-arg, k) / (factorial(k) * (2 * n + 2 * k + 1));
    }
    return result;
}

double BoysFunction::calculateZeroLevel ( double  arg)

static

Definition at line 95 of file boysfunction.cpp.

                                                  {
    if (arg < 1.0E-6){
        return 1.0;
    } else {
        arg = sqrt(arg);
        double f = 1.0/arg * erf(arg) *sqrt(M_PI)/2.0;
        return f;
    }
}

double BoysFunction::doubleFactorial ( double  n)

static

Definition at line 63 of file boysfunction.cpp.

                                             {
    if(n == -1) {
        return 1;
    }
    double result = 1;
    for(double i = n; i >= 1; i -= 2) {
        result *= i;
    }
    return result;
}

double BoysFunction::factorial ( double  n)

static

Definition at line 74 of file boysfunction.cpp.

                                       {
    if(n == 0) {
        return 1;
    }
    double result = 1;
    double startPoint = 2;
    for(double i = startPoint; i <= n; i++) {
        result *= i;
    }
    return result;
}

double BoysFunction::result

(

int

level = 0)

const

Definition at line 105 of file boysfunction.cpp.

{
    return m_results(level);
}

void BoysFunction::set	(	double	arg,
		int	levelMax = 0,
		BoysFunctionIntermediate *	intermediate = 0
	)

Definition at line 25 of file boysfunction.cpp.

{
    double limitMin = 0;
    double limitMax = 50;
    if(intermediate == 0) {
        m_intermediate = &(BoysFunctionIntermediate::getInstance());
    } else {
        m_intermediate = intermediate;
    }
    double x = arg;
    m_results = zeros(levelMax + 1);
    double expmx = exp(-x);
    if(arg < limitMin || arg > limitMax) {
        if(arg < limitMin) {
            m_results(levelMax) = calculateTaylorExpansion(arg, levelMax);
        } else if(arg > limitMax) {
            m_results(levelMax) = calculateAsymptopticForm(arg, levelMax);
        }
        // Iterate down
        for(int n = levelMax; n > 0; n--) {
            double Fn = m_results(n);
            m_results(n - 1) = (2*x*Fn + expmx) / (2*n - 1);
        }
    } else {
        // Get results from intermediate area
        for(int n = 0; n < levelMax + 1; n++) {
            m_results(n) = m_intermediate->result(arg, n);
        }
    }
}

Member Data Documentation

BoysFunctionIntermediate* BoysFunction::m_intermediate

protected

Definition at line 28 of file boysfunction.h.

vec BoysFunction::m_results

protected

Definition at line 27 of file boysfunction.h.

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

• /home/svenni/Dropbox/projects/programming/hartree-fock/hartree-fock/src/math/boysfunction.h
• /home/svenni/Dropbox/projects/programming/hartree-fock/hartree-fock/src/math/boysfunction.cpp