Package net.sf.geographiclib

Class Accumulator

java.lang.Object

net.sf.geographiclib.Accumulator

public class Accumulator
extends Object

An accumulator for sums.

This allow many double precision numbers to be added together with twice the normal precision. Thus the effective precision of the sum is 106 bits or about 32 decimal places.

The implementation follows J. R. Shewchuk, Adaptive Precision Floating-Point Arithmetic and Fast Robust Geometric Predicates, Discrete & Computational Geometry 18(3) 305–363 (1997).

In the documentation of the member functions, sum stands for the value currently held in the accumulator.

Constructor Summary

Constructors

Constructor	Description
Accumulator(double y)	Construct from a double.
Accumulator(Accumulator a)	Construct from another Accumulator.

Method Summary

Modifier and Type	Method	Description
void	Add(double y)	Add a number to the accumulator.
static void	AddInternal(Pair p, double s, double t, double y)	Internal version of Add, p = [s, t] + y
void	Negate()	Negate an accumulator.
void	Remainder(double y)	Take the remainder.
void	Set(double y)	Set the value to a double.
double	Sum()	Return the value held in the accumulator.
double	Sum(double y)	Return the result of adding a number to sum (but don't change sum).

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Accumulator

public Accumulator(double y)

Construct from a double.

Parameters:

y - set sum = y.

Accumulator

public Accumulator(Accumulator a)

Construct from another Accumulator.

Parameters:

a - set sum = a.

Method Detail

Set

public void Set(double y)

Set the value to a double.

Parameters:

y - set sum = y.

Sum

public double Sum()

Return the value held in the accumulator.

Returns:

sum.

Sum

public double Sum(double y)

Return the result of adding a number to sum (but don't change sum).

Parameters:

y - the number to be added to the sum.

Returns:

sum + y.

AddInternal

public static void AddInternal(Pair p,
                               double s,
                               double t,
                               double y)

Internal version of Add, p = [s, t] + y

Parameters:

s - the larger part of the accumulator.

t - the smaller part of the accumulator.

y - the addend.

p - output Pair(s, t) with the result.

Add

public void Add(double y)

Add a number to the accumulator.

Parameters:

y - set sum += y.

Negate

public void Negate()

Negate an accumulator.

Set sum = −sum.

Remainder

public void Remainder(double y)

Take the remainder.

Parameters:

y - the modulus

Put sum in the rangle [−y, y].