Package org.apache.commons.rng.core

Class BaseProvider

java.lang.Object

org.apache.commons.rng.core.BaseProvider

All Implemented Interfaces:

org.apache.commons.rng.RestorableUniformRandomProvider, org.apache.commons.rng.UniformRandomProvider

Direct Known Subclasses:

IntProvider, LongProvider

public abstract class BaseProvider
extends Object
implements org.apache.commons.rng.RestorableUniformRandomProvider

Base class with default implementation for common methods.

Constructor Summary

Constructors

Constructor	Description
BaseProvider()	Create an instance.

Method Summary

Modifier and Type	Method	Description
protected void	checkIndex(int min, int max, int index)	Checks whether index is in the range [min, max].
protected void	checkStateSize(byte[] state, int expected)	Deprecated. Method is used internally and should be made private in some future release.
protected byte[]	composeStateInternal(byte[] state, byte[] parentState)	Combine parent and subclass states.
protected static int[]	extendSeed(int[] seed, int length)	Extend the seed to the specified minimum length.
protected static long[]	extendSeed(long[] seed, int length)	Extend the seed to the specified minimum length.
protected void	fillState(int[] state, int[] seed)	Simple filling procedure.
protected void	fillState(long[] state, long[] seed)	Simple filling procedure.
protected byte[]	getStateInternal()	Creates a snapshot of the RNG state.
void	restoreState(org.apache.commons.rng.RandomProviderState state)
org.apache.commons.rng.RandomProviderState	saveState()
protected void	setStateInternal(byte[] state)	Resets the RNG to the given state.
protected byte[][]	splitStateInternal(byte[] state, int localStateLength)	Splits the given state into a part to be consumed by the caller in order to restore its local state, while the reminder is passed to the parent class.
String	toString()

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.UniformRandomProvider

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextBytes, nextDouble, nextDouble, nextDouble, nextFloat, nextFloat, nextFloat, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong

Constructor Detail

BaseProvider

public BaseProvider()

Create an instance.

Method Detail

saveState

public org.apache.commons.rng.RandomProviderState saveState()

Specified by:

saveState in interface org.apache.commons.rng.RestorableUniformRandomProvider

restoreState

public void restoreState(org.apache.commons.rng.RandomProviderState state)

Specified by:

restoreState in interface org.apache.commons.rng.RestorableUniformRandomProvider

toString

public String toString()

Overrides:

toString in class Object

composeStateInternal

protected byte[] composeStateInternal(byte[] state,
                                      byte[] parentState)

Combine parent and subclass states. This method must be called by all subclasses in order to ensure that state can be restored in case some of it is stored higher up in the class hierarchy. I.e. the body of the overridden getStateInternal(), will end with a statement like the following:

  
    return composeStateInternal(state,
                                super.getStateInternal());
  
 

where state is the state needed and defined by the class where the method is overridden.

Parameters:

state - State of the calling class.

parentState - State of the calling class' parent.

Returns:

the combined state. Bytes that belong to the local state will be stored at the beginning of the resulting array.

splitStateInternal

protected byte[][] splitStateInternal(byte[] state,
                                      int localStateLength)

Splits the given state into a part to be consumed by the caller in order to restore its local state, while the reminder is passed to the parent class. I.e. the body of the overridden setStateInternal(byte[]), will contain statements like the following:

  
    final byte[][] s = splitState(state, localStateLength);
    // Use "s[0]" to recover the local state.
    super.setStateInternal(s[1]);
  
 

where state is the combined state of the calling class and of all its parents.

Parameters:

state - State. The local state must be stored at the beginning of the array.

localStateLength - Number of elements that will be consumed by the locally defined state.

Returns:

the local state (in slot 0) and the parent state (in slot 1).

Throws:

IllegalStateException - if state.length < localStateLength.

getStateInternal

protected byte[] getStateInternal()

Creates a snapshot of the RNG state.

Returns:

the internal state.

setStateInternal

protected void setStateInternal(byte[] state)

Resets the RNG to the given state.

Parameters:

state - State (previously obtained by a call to getStateInternal()).

Throws:

IllegalStateException - if the size of the given array is not consistent with the state defined by this class.

See Also:

checkStateSize(byte[],int)

fillState

protected void fillState(int[] state,
                         int[] seed)

Simple filling procedure. It will

1. fill the beginning of state by copying min(seed.length, state.length) elements from seed,
2. set all remaining elements of state with non-zero values (even if seed.length < state.length).

Note: It is not recommended to use this method from a constructor as it can be overridden by subclasses possibly leading to unexpected behaviour. Future versions may remove this method, or change it to static.

Parameters:

state - State. Must be allocated.

seed - Seed. Cannot be null.

fillState

protected void fillState(long[] state,
                         long[] seed)

Simple filling procedure. It will

1. fill the beginning of state by copying min(seed.length, state.length) elements from seed,
2. set all remaining elements of state with non-zero values (even if seed.length < state.length).

Note: It is not recommended to use this method from a constructor as it can be overridden by subclasses possibly leading to unexpected behaviour. Future versions may remove this method, or change it to static.

Parameters:

state - State. Must be allocated.

seed - Seed. Cannot be null.

checkStateSize

@Deprecated
protected void checkStateSize(byte[] state,
                              int expected)

Deprecated.

Method is used internally and should be made private in some future release.

Checks that the state has the expected size.

Parameters:

state - State.

expected - Expected length of state array.

Throws:

IllegalStateException - if state.length < expected.

checkIndex

protected void checkIndex(int min,
                          int max,
                          int index)

Checks whether index is in the range [min, max].

Parameters:

min - Lower bound.

max - Upper bound.

index - Value that must lie within the [min, max] interval.

Throws:

IndexOutOfBoundsException - if index is not within the [min, max] interval.

extendSeed

protected static long[] extendSeed(long[] seed,
                                   int length)

Extend the seed to the specified minimum length. If the seed is equal or greater than the minimum length, return the same seed unchanged. Otherwise:

1. Create a new array of the specified length
2. Copy all elements of the seed into the array
3. Fill the remaining values. The additional values will have at most one occurrence of zero. If the original seed is all zero, the first extended value will be non-zero.

This method can be used in constructors that must pass their seed to the super class to avoid a duplication of seed expansion to the minimum length required by the super class and the class:

 public RNG extends AnotherRNG {
     public RNG(long[] seed) {
         super(seed = extendSeed(seed, SEED_SIZE));
         // Use seed for additional state ...
     }
 }
 

Note using the state filling procedure provided in fillState(long[], long[]) is not possible as it is an instance method. Calling a seed extension routine must use a static method.

This method functions as if the seed has been extended using a SplitMix64 generator seeded with seed[0], or zero if the input seed length is zero.

 if (seed.length < length) {
     final long[] s = Arrays.copyOf(seed, length);
     final SplitMix64 rng = new SplitMix64(s[0]);
     for (int i = seed.length; i < length; i++) {
         s[i] = rng.nextLong();
     }
     return s;
 }

Parameters:

seed - Input seed

length - The minimum length

Returns:

the seed

Since:

1.5

extendSeed

protected static int[] extendSeed(int[] seed,
                                  int length)

Extend the seed to the specified minimum length. If the seed is equal or greater than the minimum length, return the same seed unchanged. Otherwise:

1. Create a new array of the specified length
2. Copy all elements of the seed into the array
3. Fill the remaining values. The additional values will have at most one occurrence of zero. If the original seed is all zero, the first extended value will be non-zero.

This method can be used in constructors that must pass their seed to the super class to avoid a duplication of seed expansion to the minimum length required by the super class and the class:

 public RNG extends AnotherRNG {
     public RNG(int[] seed) {
         super(seed = extendSeed(seed, SEED_SIZE));
         // Use seed for additional state ...
     }
 }
 

Note using the state filling procedure provided in fillState(int[], int[]) is not possible as it is an instance method. Calling a seed extension routine must use a static method.

This method functions as if the seed has been extended using a SplitMix64-style 32-bit generator seeded with seed[0], or zero if the input seed length is zero. The generator uses the 32-bit mixing function from MurmurHash3.

Parameters:

seed - Input seed

length - The minimum length

Returns:

the seed

Since:

1.5