org.primordion.xholon.util
Class Random

java.lang.Object
  org.primordion.xholon.util.Random

public class Random

extends java.lang.Object

Encapsulates the colt library's random number generation. The Random class consolidates all the random number distributions provided by the colt library into a single class. The intent here is two-fold - to provide easier access to these distributions and more importantly to insure that each distribution uses the same random number stream, allowing for easily repeatable behavoir of random number generation.

Random contains a variety of random number distributions as static instance variables as well as a few next* methods for returning the next psuedo-random value from a distribution. Before using any of the instance variable distributions, these distributions must be created via the appropriate create* method. For example,

 // initialize Random.uniform
 Random.createUniform();

 // Random.uniform is now initialized and can be used.
 int index = Random.uniform.getNextIntFromTo(0, 100);
 

Once created a distribution can be used anywhere in your code through the use of Random's static instance variables. So for example, if you create the Uniform distribution in your model's begin() method, you can access the same Uniform distribution in your model's agent code with Random.uniform. This instance variable should always be referenced as such, that is, as Random., and not as the right hand side of an assignment. Assigning a variable in this way can lead to unpredictable results when setting the random seed.

All the distributions in Random are from the colt library. The instance variable name is the same as the corresponding colt object with the first character in lower case. For example, the Zeta distribution is called zeta. See the colt library documentation in repast/docs/colt for more information about these distributions. The next* methods can be used as is, without creating a distribution before hand. For example,

 double s = Random.nextCauchy();
 

Random also allows you to set and get the random seed as well as the random number generator associated with that seed. Setting a new seed with setSeed will create a new random number generator and invalidate any previously created distributions. If you wish to use a distribution after the seed has been set, you must create it as described above. All of the distributions contained by Random will use the same generator - a MersenneTwister. Consequently, once the seed is set all the distributions will use the same generator, same random number stream and repeatable randomness can be easily achieved.

Note that Random creates a default random number generator using the current timestamp as the seed. If you do not explicitly set your own seed, the distributions created via the create* calls will use this default generator.

See Also:

"The RePast random how to in repast/docs/how_to/random.html", "The colt library docs in repast/docs/colt/index.html"

Field Summary

static cern.jet.random.Beta	beta
static cern.jet.random.Binomial	binomial
static cern.jet.random.BreitWigner	breitWigner
static cern.jet.random.BreitWignerMeanSquare	breitWignerMeanSquare
static cern.jet.random.ChiSquare	chiSquare
static cern.jet.random.Empirical	empirical
static cern.jet.random.EmpiricalWalker	empiricalWalker
static cern.jet.random.Exponential	exponential
static cern.jet.random.ExponentialPower	exponentialPower
static cern.jet.random.Gamma	gamma
static cern.jet.random.Hyperbolic	hyperbolic
static cern.jet.random.HyperGeometric	hyperGeometric
static int	LINEAR_INTERPOLATION
static cern.jet.random.Logarithmic	logarithmic
static cern.jet.random.NegativeBinomial	negativeBinomial
static int	NO_INTERPOLATIONN
static cern.jet.random.Normal	normal
static cern.jet.random.Poisson	poisson
static cern.jet.random.PoissonSlow	poissonSlow
static cern.jet.random.StudentT	studentT
static cern.jet.random.Uniform	uniform
static cern.jet.random.VonMises	vonMises
static cern.jet.random.Zeta	zeta

Constructor Summary

Random()

Method Summary

static void	createBeta(double alpha, double beta)
static void	createBinomial(int n, double p)
static void	createBreitWigner(double mean, double gamma, double cut)
static void	createBreitWignerMeanSquareState(double mean, double gamma, double cut)
static void	createChiSquare(double freedom)
static void	createEmpirical(double[] pdf, int interpolationType)
static void	createEmpiricalWalker(double[] pdf, int interpolationType)
static void	createExponential(double lambda)
static void	createExponentialPower(double tau)
static void	createGamma(double alpha, double lambda)
static void	createHyperbolic(double alpha, double beta)
static void	createHyperGeometric(int N, int s, int n)
static void	createLogarithmic(double p)
static void	createNegativeBinomial(int n, double p)
static void	createNormal(double mean, double standardDeviation)
static void	createPoisson(double mean)
static void	createPoissonSlow(double mean)
static void	createStudentT(double freedom)
static void	createUniform()
static void	createUniform(double min, double max)
static void	createVonMises(double freedom)
static void	createZeta(double ro, double pk)
static cern.jet.random.engine.RandomEngine	generateNewSeed() Generates a new random number generator using the the current timestamp as a the seed.
static double	geometricPdf(int k, double p)
static cern.jet.random.engine.RandomEngine	getGenerator() Gets the current random number generator.
static cern.jet.random.engine.RandomEngine	getGenerator(long seed) Creates a new random number generator with the specified seed and returns this new generator.
static long	getSeed() Gets the current randon number generator seed.
static double	nextBurr1(double r, int nr)
static double	nextBurr2(double r, double k, int nr)
static double	nextCauchy()
static double	nextErlang(double variance, double mean)
static int	nextGeometric(double p)
static double	nextLambda(double l3, double l4)
static double	nextLaplace()
static double	nextLogistic()
static double	nextPowLaw(double alpha, double cut)
static double	nextTriangular()
static double	nextWeibull(double alpha, double beta)
static int	nextZipfInt(double z)
static void	setSeed(long seed) Creates a new random number generator with the specified seed.

Methods inherited from class java.lang.Object

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

Field Detail

LINEAR_INTERPOLATION

public static final int LINEAR_INTERPOLATION

See Also:

Constant Field Values

NO_INTERPOLATIONN

public static final int NO_INTERPOLATIONN

See Also:

Constant Field Values

beta

public static cern.jet.random.Beta beta

binomial

public static cern.jet.random.Binomial binomial

breitWigner

public static cern.jet.random.BreitWigner breitWigner

breitWignerMeanSquare

public static cern.jet.random.BreitWignerMeanSquare breitWignerMeanSquare

chiSquare

public static cern.jet.random.ChiSquare chiSquare

empirical

public static cern.jet.random.Empirical empirical

empiricalWalker

public static cern.jet.random.EmpiricalWalker empiricalWalker

exponential

public static cern.jet.random.Exponential exponential

exponentialPower

public static cern.jet.random.ExponentialPower exponentialPower

gamma

public static cern.jet.random.Gamma gamma

hyperbolic

public static cern.jet.random.Hyperbolic hyperbolic

hyperGeometric

public static cern.jet.random.HyperGeometric hyperGeometric

logarithmic

public static cern.jet.random.Logarithmic logarithmic

negativeBinomial

public static cern.jet.random.NegativeBinomial negativeBinomial

normal

public static cern.jet.random.Normal normal

poisson

public static cern.jet.random.Poisson poisson

poissonSlow

public static cern.jet.random.PoissonSlow poissonSlow

studentT

public static cern.jet.random.StudentT studentT

uniform

public static cern.jet.random.Uniform uniform

vonMises

public static cern.jet.random.VonMises vonMises

zeta

public static cern.jet.random.Zeta zeta

Constructor Detail

Random

public Random()

Method Detail

geometricPdf

public static double geometricPdf(int k,
                                  double p)

nextBurr1

public static double nextBurr1(double r,
                               int nr)

nextBurr2

public static double nextBurr2(double r,
                               double k,
                               int nr)

nextCauchy

public static double nextCauchy()

nextErlang

public static double nextErlang(double variance,
                                double mean)

nextGeometric

public static int nextGeometric(double p)

nextLambda

public static double nextLambda(double l3,
                                double l4)

nextLaplace

public static double nextLaplace()

nextLogistic

public static double nextLogistic()

nextPowLaw

public static double nextPowLaw(double alpha,
                                double cut)

nextTriangular

public static double nextTriangular()

nextWeibull

public static double nextWeibull(double alpha,
                                 double beta)

nextZipfInt

public static int nextZipfInt(double z)

createZeta

public static void createZeta(double ro,
                              double pk)

createVonMises

public static void createVonMises(double freedom)

createUniform

public static void createUniform(double min,
                                 double max)

createUniform

public static void createUniform()

createStudentT

public static void createStudentT(double freedom)

createPoissonSlow

public static void createPoissonSlow(double mean)

createPoisson

public static void createPoisson(double mean)

createNormal

public static void createNormal(double mean,
                                double standardDeviation)

createNegativeBinomial

public static void createNegativeBinomial(int n,
                                          double p)

createLogarithmic

public static void createLogarithmic(double p)

createHyperGeometric

public static void createHyperGeometric(int N,
                                        int s,
                                        int n)

createHyperbolic

public static void createHyperbolic(double alpha,
                                    double beta)

createGamma

public static void createGamma(double alpha,
                               double lambda)

createExponentialPower

public static void createExponentialPower(double tau)

createExponential

public static void createExponential(double lambda)

createEmpiricalWalker

public static void createEmpiricalWalker(double[] pdf,
                                         int interpolationType)

createEmpirical

public static void createEmpirical(double[] pdf,
                                   int interpolationType)

createChiSquare

public static void createChiSquare(double freedom)

createBreitWignerMeanSquareState

public static void createBreitWignerMeanSquareState(double mean,
                                                    double gamma,
                                                    double cut)

createBreitWigner

public static void createBreitWigner(double mean,
                                     double gamma,
                                     double cut)

createBinomial

public static void createBinomial(int n,
                                  double p)

createBeta

public static void createBeta(double alpha,
                              double beta)

generateNewSeed

public static cern.jet.random.engine.RandomEngine generateNewSeed()

Generates a new random number generator using the the current timestamp as a the seed. This will invalidate any previously created distributions.

getGenerator

public static cern.jet.random.engine.RandomEngine getGenerator()

Gets the current random number generator.

getGenerator

public static cern.jet.random.engine.RandomEngine getGenerator(long seed)

Creates a new random number generator with the specified seed and returns this new generator. This will invalidate any previously created distributions.

Parameters:

seed - the new generator seed

Returns:

the new generator

setSeed

public static void setSeed(long seed)

Creates a new random number generator with the specified seed. This will invalidate any previously created distributions.

Parameters:

seed - the seed for the new generator

getSeed

public static long getSeed()

Gets the current randon number generator seed.