cacheperf

Class ScrambledZipfianGenerator

java.lang.Object

java.util.Random

cacheperf.ScrambledZipfianGenerator

All Implemented Interfaces:

Serializable

public class ScrambledZipfianGenerator
extends Random

A generator of a zipfian distribution. It produces a sequence of items, such that some items are more popular than others, according to a zipfian distribution. When you construct an instance of this class, you specify the number of items in the set to draw from, either by specifying an itemcount (so that the sequence is of items from 0 to itemcount-1) or by specifying a min and a max (so that the sequence is of items from min to max inclusive). After you construct the instance, you can change the number of items by calling nextInt(itemcount) or nextLong(itemcount). Unlike @ZipfianGenerator, this class scatters the "popular" items across the itemspace. Use this, instead of @ZipfianGenerator, if you don't want the head of the distribution (the popular items) clustered together.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static long	FNV_offset_basis_64
static long	FNV_prime_64
static long	ITEM_COUNT
static double	USED_ZIPFIAN_CONSTANT
static double	ZETAN

Constructor Summary

Constructors

Constructor and Description
ScrambledZipfianGenerator(long _items) Create a zipfian generator for the specified number of items.
ScrambledZipfianGenerator(long _min, long _max) Create a zipfian generator for items between min and max.
ScrambledZipfianGenerator(long min, long max, double _zipfianconstant) Create a zipfian generator for items between min and max (inclusive) for the specified zipfian constant.

Method Summary

Modifier and Type	Method and Description
static long	FNVhash64(long val) 64 bit FNV hash.
static void	main(String[] args)
int	nextInt() Return the next int in the sequence.
long	nextLong() Return the next long in the sequence.

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, next, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, setSeed

Methods inherited from class java.lang.Object

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

Field Detail

ZETAN

public static final double ZETAN

See Also:

Constant Field Values

USED_ZIPFIAN_CONSTANT

public static final double USED_ZIPFIAN_CONSTANT

See Also:

Constant Field Values

ITEM_COUNT

public static final long ITEM_COUNT

See Also:

Constant Field Values

FNV_offset_basis_64

public static final long FNV_offset_basis_64

See Also:

Constant Field Values

FNV_prime_64

public static final long FNV_prime_64

See Also:

Constant Field Values

Constructor Detail

ScrambledZipfianGenerator

public ScrambledZipfianGenerator(long _items)

Create a zipfian generator for the specified number of items.

Parameters:

_items - The number of items in the distribution.

ScrambledZipfianGenerator

public ScrambledZipfianGenerator(long _min,
                                 long _max)

Create a zipfian generator for items between min and max.

Parameters:

_min - The smallest integer to generate in the sequence.

_max - The largest integer to generate in the sequence.

ScrambledZipfianGenerator

public ScrambledZipfianGenerator(long min,
                                 long max,
                                 double _zipfianconstant)

Create a zipfian generator for items between min and max (inclusive) for the specified zipfian constant. If you use a zipfian constant other than 0.99, this will take a long time to complete because we need to recompute zeta.

Parameters:

min - The smallest integer to generate in the sequence.

max - The largest integer to generate in the sequence.

_zipfianconstant - The zipfian constant to use.

Method Detail

nextInt

public int nextInt()

Return the next int in the sequence.

Overrides:

nextInt in class Random

nextLong

public long nextLong()

Return the next long in the sequence.

Overrides:

nextLong in class Random

main

public static void main(String[] args)

FNVhash64

public static long FNVhash64(long val)

64 bit FNV hash. Produces more "random" hashes than (say) String.hashCode().

Parameters:

val - The value to hash.

Returns:

The hash value