java.lang.Object
- de.gsi.math.TRandom

Direct Known Subclasses:

TRandom1, TRandom3
```
public class TRandom
extends java.lang.Object
```
TRandom basic Random number generator class (periodicity = 10**9). Note that this is a very simple generator (linear congruential) which is known to have defects (the lower random bits are correlated) and therefore should NOT be used in any statistical study. One should use instead TRandom1, TRandom2 or TRandom3. TRandom3, is based on the "Mersenne Twister generator", and is the recommended one, since it has good random proprieties (period of about 10**6000 ) and it is fast. TRandom1, based on the RANLUX algorithm, has mathematically proven random proprieties and a period of about 10**171. It is however slower than the others. TRandom2, is based on the Tausworthe generator of L'Ecuyer, and it has the advantage of being fast and using only 3 words (of 32 bits) for the state. The period is 10**26. The following basic Random distributions are provided: ===================================================

See Also:

Exp(double), Integer(long), Gaus(double, double), Rndm(), Uniform(double), Landau(double, double), Poisson(double), Binomial(int, double)

Field Summary

Fields
Modifier and Type Field Description

protected static long fSeed

Constructor Summary

Constructors
Constructor Description

TRandom(long seed)
default constructor

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static int`	`Binomial(int ntot, double prob)`
`static double`	`BreitWigner(double mean, double gamma)`	Return a number distributed following a BreitWigner function with mean and gamma
`static void`	`Circle(double[] val, double r)`	generates random vectors, uniformly distributed over a circle of given radius.
`static double`	`Exp(double tau)`
`static double`	`Gaus(double mean, double sigma)`	samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigma.
`static long`	`Integer(long imax)`	returns a random integer on [ 0, imax-1 ].
`static double`	`Landau(double mpv, double sigma)`	Generate a random number following a Landau distribution with mpv(most probable value) and sigma Converted by Rene Brun from CERNLIB routine ranlan(G110)
`static int`	`Poisson(double mean)`	Generates a random integer N according to a Poisson law.
`static double`	`PoissonD(double mean)`	Generates a random number according to a Poisson law.
`static void`	`Rannor(double[] val)`	Return 2 numbers distributed following a gaussian with mean=0 and sigma=1
`static void`	`Rannor(float[] val)`	Return 2 numbers distributed following a gaussian with mean=0 and sigma=1
`static double`	`Rndm()`	Machine independent random number generator.
`void`	`RndmArray(int n, float[] array)`	Return an array of n random numbers uniformly distributed in ]0,1]
`void`	`SetSeed(long seed)`	Set the random generator seed if seed is zero, the seed is set to the current machine clock Note that the machine clock is returned with a precision of 1 second.
`static void`	`Sphere(double[] val, double r)`	generates random vectors, uniformly distributed over the surface of a sphere of given radius.
`java.lang.String`	`toString()`
`static double`	`Uniform(double x1)`	returns a uniform deviate on the interval ]0, x1].
`static double`	`Uniform(double x1, double x2)`	returns a uniform deviate on the interval ]x1, x2].

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - fSeed
```
protected static long fSeed
```
- Constructor Detail
  - TRandom
```
public TRandom(long seed)
```
    default constructor
    
    Parameters:
    
    seed - initial seed
- Method Detail
  - Binomial
```
public static int Binomial(int ntot,
                           double prob)
```
  - BreitWigner
```
public static double BreitWigner(double mean,
                                 double gamma)
```
    Return a number distributed following a BreitWigner function with mean and gamma
    
    Parameters:
    
    mean - center of Breit-Wigner distribution
    
    gamma - width of Breit-Wigner distribution
    
    Returns:
    
    number distributed following a BreitWigner function
  - Circle
```
public static void Circle(double[] val,
                          double r)
```
    generates random vectors, uniformly distributed over a circle of given radius.
    
    Parameters:
    
    val - [0], [1] a random 2-d vector of length r
    
    r - circle radius
  - Exp
```
public static double Exp(double tau)
```
    Parameters:
    
    tau - parameter
    
    Returns:
    
    exponential deviate. exp( -t/tau )
  - Gaus
```
public static double Gaus(double mean,
                          double sigma)
```
    samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigma. Uses the Acceptance-complement ratio from W. Hoermann and G. Derflinger This is one of the fastest existing method for generating normal random variables. It is a factor 2/3 faster than the polar (Box-Muller) method used in the previous version of Gaus. The speed is comparable to the Ziggurat method (from Marsaglia) implemented for example in GSL and available in the MathMore library. REFERENCE: W. Hoermann and G. Derflinger (1990): The ACR Method for generating normal random variables, OR Spektrum 12 (1990), 181-185. Implementation taken from UNURAN (c) 2000 W. Hoermann & J. Leydold, Institut f. Statistik, WU Wien
    
    Parameters:
    
    mean - centre of Gauss function
    
    sigma - width of Gauss function
    
    Returns:
    
    random number from the standard Normal (Gaussian) Distribution
  - Integer
```
public static long Integer(long imax)
```
    returns a random integer on [ 0, imax-1 ].
    
    Parameters:
    
    imax - max range
    
    Returns:
    
    random integer on [ 0, imax-1 ]
  - Landau
```
public static double Landau(double mpv,
                            double sigma)
```
    Generate a random number following a Landau distribution with mpv(most probable value) and sigma Converted by Rene Brun from CERNLIB routine ranlan(G110)
    
    Parameters:
    
    mpv - parameter of Landau distribution
    
    sigma - parameter of Landau distribution
    
    Returns:
    
    random number following a Landau distribution
  - Poisson
```
public static int Poisson(double mean)
```
    Generates a random integer N according to a Poisson law. Prob(N) = exp(-mean)*mean^N/Factorial(N) Use a different procedure according to the mean value. The algorithm is the same used by CLHEP For lower value (mean < 25) use the rejection method based on the exponential For higher values use a rejection method comparing with a Lorentzian distribution, as suggested by several authors This routine since is returning 32 bits integer will not work for values larger than 2*10**9 One should then use the TRandom.PoissonD for such large values
    
    Parameters:
    
    mean - centre of distribution
    
    Returns:
    
    random integer N according to a Poisson law
  - PoissonD
```
public static double PoissonD(double mean)
```
    Generates a random number according to a Poisson law. Prob(N) = exp(-mean)*mean^N/Factorial(N) This function is a variant of Poisson returning a double instead of an integer.
    
    Parameters:
    
    mean - centre of distribution
    
    Returns:
    
    random number according to a Poisson law
  - Rannor
```
public static void Rannor(double[] val)
```
    Return 2 numbers distributed following a gaussian with mean=0 and sigma=1
    
    Parameters:
    
    val - storage vector for Gaussian distributed random numbers
  - Rannor
```
public static void Rannor(float[] val)
```
    Return 2 numbers distributed following a gaussian with mean=0 and sigma=1
    
    Parameters:
    
    val - storage vector for Rannor distributed random numbers
  - Rndm
```
public static double Rndm()
```
    Machine independent random number generator. Based on the BSD Unix (Rand) Linear congrential generator Produces uniformly-distributed floating points between 0 and 1. Identical sequence on all machines of >= 32 bits. Periodicity = 2**31 generates a number in ]0,1] Note that this is a generator which is known to have defects (the lower random bits are correlated) and therefore should NOT be used in any statistical study.
    
    Returns:
    
    machine independent random number
  - RndmArray
```
public void RndmArray(int n,
                      float[] array)
```
    Return an array of n random numbers uniformly distributed in ]0,1]
    
    Parameters:
    
    n - length of array
    
    array - storage array
  - SetSeed
```
public void SetSeed(long seed)
```
    Set the random generator seed if seed is zero, the seed is set to the current machine clock Note that the machine clock is returned with a precision of 1 second. If one calls SetSeed(0) within a loop and the loop time is less than 1s, all generated numbers will be identical!
    
    Parameters:
    
    seed - initial seed
  - Sphere
```
public static void Sphere(double[] val,
                          double r)
```
    generates random vectors, uniformly distributed over the surface of a sphere of given radius. Method: (based on algorithm suggested by Knuth and attributed to Robert E Knop) which uses less random numbers than the CERNLIB RN23DIM algorithm
    
    Parameters:
    
    val - [0], [1], [2] a random 3-d vector of length r
    
    r - sphere radius
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - Uniform
```
public static double Uniform(double x1)
```
    returns a uniform deviate on the interval ]0, x1].
    
    Parameters:
    
    x1 - maximum range
    
    Returns:
    
    uniform deviate on the interval ]0, x1]
  - Uniform
```
public static double Uniform(double x1,
                             double x2)
```
    returns a uniform deviate on the interval ]x1, x2].
    
    Parameters:
    
    x1 - minimum range
    
    x2 - maximum range
    
    Returns:
    
    uniform deviate on the interval ]x1, x2]

Class TRandom

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

fSeed

Constructor Detail

TRandom

Method Detail

Binomial

BreitWigner

Circle

Exp

Gaus

Integer

Landau

Poisson

PoissonD

Rannor

Rannor

Rndm

RndmArray

SetSeed

Sphere

toString

Uniform

Uniform