net.myrrix.common.random

Class RandomUtils

java.lang.Object

net.myrrix.common.random.RandomUtils

public final class RandomUtils
extends Object

Helpful methods related to randomness and related functions. Some parts derived from Mahout.

Author:

Sean Owen, Mahout

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_INT_SMALLER_TWIN_PRIME The largest prime less than 231-1 that is the smaller of a twin prime pair.

Method Summary

Methods

Modifier and Type	Method and Description
static long	md5HashToLong(long l)
static int	nextTwinPrime(int n) Finds next-largest "twin primes": numbers p and p+2 such that both are prime.
static int	randomFrom(FastIDSet set, org.apache.commons.math3.random.RandomGenerator random)
static float[]	randomUnitVector(int dimensions, org.apache.commons.math3.random.RandomGenerator random)

Methods inherited from class java.lang.Object

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

Field Detail

MAX_INT_SMALLER_TWIN_PRIME

public static final int MAX_INT_SMALLER_TWIN_PRIME

The largest prime less than 2³¹-1 that is the smaller of a twin prime pair.

See Also:

Constant Field Values

Method Detail

randomUnitVector

public static float[] randomUnitVector(int dimensions,
                       org.apache.commons.math3.random.RandomGenerator random)

Parameters:

dimensions - dimensionality of resulting vector

random - random number generator to use

Returns:

a vector of length 1 over the given number of dimensions, whose direction is chosen uniformly at random (that is: a point chosen uniformly at random on the unit hypersphere)

nextTwinPrime

public static int nextTwinPrime(int n)

Finds next-largest "twin primes": numbers p and p+2 such that both are prime. Finds the smallest such p such that the smaller twin, p, is greater than or equal to n. Returns p+2, the larger of the two twins.

md5HashToLong

public static long md5HashToLong(long l)

randomFrom

public static int randomFrom(FastIDSet set,
             org.apache.commons.math3.random.RandomGenerator random)

Parameters:

set - to choose from

random - random number generator

Returns:

element of the set chosen uniformly at random