org.jgap.util

Class randomLEcuyer

java.lang.Object

org.jgap.util.randomX

org.jgap.util.randomLEcuyer

public class randomLEcuyer
extends randomX

Implementation of a randomX-compliant class using L'Ecuyer's two-sequence generator with a Bays-Durham shuffle, as described on page 282 of Press et al., Numerical Recipes in C, 2nd edition. Their implementation was constrained by the absence of a 64-bit integer data type. Since Java guarantees a long to be 64 bit, we can use L'Ecuyer's multiplier and modulus directly, rather than flailing around with Schrage's algorithm. Further, 64-bit long arithmetic allows us to directly combine the results from the two generators by adding and taking the modulus of one of them, bypassing the subtract and test for negative gimmick used in Numerical Recipes.

For additional details, see L'Ecuyer's original 1968 paper at page 742 of Communications of the ACM, Vol. 31.

Designed and implemented in July 1996 by John Walker, kelvin@fourmilab.ch.

Constructor Summary

Constructors

Constructor and Description
randomLEcuyer() Creates a new pseudorandom number generator, seeded from the current time.
randomLEcuyer(long seed) Creates a new pseudorandom number generator with a specified nonzero seed.

Method Summary

Modifier and Type	Method and Description
byte	nextByte() Get next byte from generator.
void	setSeed(long seed) Set seed for generator.

Methods inherited from class org.jgap.util.randomX

nextBit, nextByte, nextByte, nextDouble, nextFloat, nextGaussian, nextInt, nextLong, nextShort, setSeed

Methods inherited from class java.lang.Object

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

Constructor Detail

randomLEcuyer

public randomLEcuyer()

Creates a new pseudorandom number generator, seeded from the current time.

randomLEcuyer

public randomLEcuyer(long seed)
              throws java.lang.IllegalArgumentException

Creates a new pseudorandom number generator with a specified nonzero seed.

Parameters:

seed - initial seed for the generator

Throws:

java.lang.IllegalArgumentException

Method Detail

setSeed

public void setSeed(long seed)
             throws java.lang.IllegalArgumentException

Set seed for generator. Subsequent values will be based on the given nonzero seed.

Parameters:

seed - seed for the generator

Throws:

java.lang.IllegalArgumentException

nextByte

public byte nextByte()

Get next byte from generator.

Specified by:

nextByte in class randomX

Returns:

the next byte from the generator.