ExponentialHash.cpp File Reference

Code for generating an exponentially distributed hash function. More...

#include <stdlib.h>
#include <math.h>
#include <algorithm>
#include "defines.h"

Macros
#define	clip(x, a, b)   min(max(x, a), b)
	Clip x to [a,b].

Functions
float	UniformHash (unsigned int x, unsigned int max)
	Uniform hash. More...
float	ExpHash (unsigned int x, unsigned int max)
	Exponential hash. More...
float	ExpHash (unsigned int x, unsigned int y, unsigned int m, float omega)
	Exponential hash with control of exponent and tail of distribution. More...

Function Documentation

ExpHash() [1/2]

float ExpHash	(	unsigned int	x,
		unsigned int	max
	)

Exponentially distributed hash function.

Hash an unsigned integer into the range (0, 1) with an exponential distribution.

Parameters

x	Value to be hashed.
max	Largest possible value of x.

Returns

An exponentially distributed hash value > 0 and < 1.

ExpHash() [2/2]

float ExpHash	(	unsigned int	x,
		unsigned int	y,
		unsigned int	m,
		float	omega
	)

Exponentially distributed hash function.

Hash an unsigned integer into the range (0, 1) with an exponential distribution giving some control over the base of the exponent and the height of the tail of the distribution.

Parameters

x	Value to be hashed.
y	Second value to be hashed to select distribution.
m	Largest possible value of x.
omega	The tail multiplier, which controls how low the tails of the distribution can be.

Returns

An exponentially distributed random number > 0 and < 1.

UniformHash()

float UniformHash	(	unsigned int	x,
		unsigned int	max
	)

Uniformly distributed hash function.

Hash an unsigned integer uniformly into the range (0, 1).

Parameters

x	Value to be hashed.
max	Largest possible value of x.

Returns

A uniformly distributed hash value > 0 and < 1.