Package org.apache.commons.rng.sampling.distribution

Class UniformLongSampler

java.lang.Object

org.apache.commons.rng.sampling.distribution.UniformLongSampler

All Implemented Interfaces:

LongSampler, SharedStateLongSampler, SharedStateSampler<SharedStateLongSampler>

Direct Known Subclasses:

UniformLongSampler.FixedUniformLongSampler, UniformLongSampler.LargeRangeUniformLongSampler, UniformLongSampler.OffsetUniformLongSampler, UniformLongSampler.PowerOf2RangeUniformLongSampler, UniformLongSampler.SmallRangeUniformLongSampler

public abstract class UniformLongSampler
extends java.lang.Object
implements SharedStateLongSampler

Discrete uniform distribution sampler generating values of type long.

Sampling uses UniformRandomProvider.nextLong().

When the range is a power of two the number of calls is 1 per sample. Otherwise a rejection algorithm is used to ensure uniformity. In the worst case scenario where the range spans half the range of a long (2⁶³ + 1) the expected number of calls is 2 per sample.

Since:

1.4

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	UniformLongSampler.FixedUniformLongSampler	Discrete uniform distribution sampler when the sample value is fixed.
private static class	UniformLongSampler.LargeRangeUniformLongSampler	Discrete uniform distribution sampler when the range between lower and upper is too large to fit in a positive long.
private static class	UniformLongSampler.OffsetUniformLongSampler	Adds an offset to an underlying discrete sampler.
private static class	UniformLongSampler.PowerOf2RangeUniformLongSampler	Discrete uniform distribution sampler when the range is a power of 2 and greater than 1.
private static class	UniformLongSampler.SmallRangeUniformLongSampler	Discrete uniform distribution sampler when the range is small enough to fit in a positive long.

Field Summary

Fields

Modifier and Type	Field	Description
protected UniformRandomProvider	rng	Underlying source of randomness.

Constructor Summary

Constructors

Constructor	Description
UniformLongSampler(UniformRandomProvider rng)

Method Summary

Modifier and Type	Method	Description
private static UniformLongSampler	createZeroBoundedSampler(UniformRandomProvider rng, long upper)	Create a new sampler for the range 0 inclusive to upper inclusive.
private static boolean	isPowerOf2(long value)	Checks if the value is a power of 2.
static UniformLongSampler	of(UniformRandomProvider rng, long lower, long upper)	Creates a new discrete uniform distribution sampler.
java.lang.String	toString()
abstract UniformLongSampler	withUniformRandomProvider(UniformRandomProvider rng)	Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.rng.sampling.distribution.LongSampler

sample, samples, samples

Field Detail

rng

protected final UniformRandomProvider rng

Underlying source of randomness.

Constructor Detail

UniformLongSampler

UniformLongSampler(UniformRandomProvider rng)

Parameters:

rng - Generator of uniformly distributed random numbers.

Method Detail

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

withUniformRandomProvider

public abstract UniformLongSampler withUniformRandomProvider(UniformRandomProvider rng)

Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Specified by:

withUniformRandomProvider in interface SharedStateSampler<SharedStateLongSampler>

Parameters:

rng - Generator of uniformly distributed random numbers.

Returns:

the sampler

of

public static UniformLongSampler of(UniformRandomProvider rng,
                                    long lower,
                                    long upper)

Creates a new discrete uniform distribution sampler.

Parameters:

rng - Generator of uniformly distributed random numbers.

lower - Lower bound (inclusive) of the distribution.

upper - Upper bound (inclusive) of the distribution.

Returns:

the sampler

Throws:

java.lang.IllegalArgumentException - if lower > upper.

createZeroBoundedSampler

private static UniformLongSampler createZeroBoundedSampler(UniformRandomProvider rng,
                                                           long upper)

Create a new sampler for the range 0 inclusive to upper inclusive.

This can handle any positive upper.

Parameters:

rng - Generator of uniformly distributed random numbers.

upper - Upper bound (inclusive) of the distribution. Must be positive.

Returns:

the sampler

isPowerOf2

private static boolean isPowerOf2(long value)

Checks if the value is a power of 2.

This returns true for the value Long.MIN_VALUE which can be handled as an unsigned long of 2^63.

Parameters:

value - Value.

Returns:

true if a power of 2