Discrete Distributions

Description

Random variate generators for discrete distributions.

Classes
class	cIntUniform
	Generates random numbers from the discrete uniform distribution. More...
class	cIntUniformExcl
	Generates random numbers from the discrete uniform distribution. More...
class	cBernoulli
	Generates random numbers that are the results of Bernoulli trials. More...
class	cBinomial
	Generates random numbers from the binomial distribution. More...
class	cGeometric
	Generates random numbers from the geometric distribution. More...
class	cNegBinomial
	Generates random numbers from the negative binomial distribution. More...
class	cPoisson
	Generates random numbers from the Poisson distribution. More...

Functions
SIM_API int	intuniform (cRNG *rng, int a, int b)
	Returns a random integer with uniform distribution in the range [a,b], inclusive. (Note that the function can also return b.) More...
SIM_API int	intuniformexcl (cRNG *rng, int a, int b)
	Returns a random integer with uniform distribution over [a,b), that is, from [a,b-1]. More...
int	bernoulli (cRNG *rng, double p)
	Returns the result of a Bernoulli trial with probability p, that is, 1 with probability p and 0 with probability (1-p). More...
SIM_API int	binomial (cRNG *rng, int n, double p)
	Returns a random integer from the binomial distribution with parameters n and p, that is, the number of successes in n independent trials with probability p. More...
SIM_API int	geometric (cRNG *rng, double p)
	Returns a random integer from the geometric distribution with parameter p, that is, the number of independent trials with probability p until the first success. More...
SIM_API int	negbinomial (cRNG *rng, int n, double p)
	Returns a random integer from the negative binomial distribution with parameters n and p, that is, the number of failures occurring before n successes in independent trials with probability p of success. More...
SIM_API int	poisson (cRNG *rng, double lambda)
	Returns a random integer from the Poisson distribution with parameter lambda, that is, the number of arrivals over unit time where the time between successive arrivals follow exponential distribution with parameter lambda. More...

Function Documentation

intuniform()

SIM_API int omnetpp::intuniform	(	cRNG *	rng,
		int	a,
		int	b
	)

Returns a random integer with uniform distribution in the range [a,b], inclusive. (Note that the function can also return b.)

Parameters

a,b	the interval, a<b
rng	the underlying random number generator

Referenced by cComponent::intuniform(), and omnetpp::lognormal().

intuniformexcl()

SIM_API int omnetpp::intuniformexcl	(	cRNG *	rng,
		int	a,
		int	b
	)

Returns a random integer with uniform distribution over [a,b), that is, from [a,b-1].

Parameters

a,b	the interval, a<b
rng	the underlying random number generator

Referenced by cComponent::intuniformexcl(), and omnetpp::lognormal().

bernoulli()

int omnetpp::bernoulli ( cRNG *  rng, double  p  )

inline

Returns the result of a Bernoulli trial with probability p, that is, 1 with probability p and 0 with probability (1-p).

Generation is using elementary look-up.

Parameters

p	0=<p<=1
rng	the underlying random number generator

References omnetpp::binomial(), cRNG::doubleRand(), omnetpp::geometric(), omnetpp::negbinomial(), and omnetpp::poisson().

Referenced by cComponent::bernoulli().

binomial()

SIM_API int omnetpp::binomial	(	cRNG *	rng,
		int	n,
		double	p
	)

Returns a random integer from the binomial distribution with parameters n and p, that is, the number of successes in n independent trials with probability p.

Generation is using the relationship to Bernoulli distribution (runtime is proportional to n).

Parameters

n	n>=0
p	0<=p<=1
rng	the underlying random number generator

Referenced by omnetpp::bernoulli(), and cComponent::binomial().

geometric()

SIM_API int omnetpp::geometric	(	cRNG *	rng,
		double	p
	)

Returns a random integer from the geometric distribution with parameter p, that is, the number of independent trials with probability p until the first success.

This is the n=1 special case of the negative binomial distribution.

Generation uses inverse transform.

Parameters

p	0<p<=1
rng	the underlying random number generator

Referenced by omnetpp::bernoulli(), and cComponent::geometric().

negbinomial()

SIM_API int omnetpp::negbinomial	(	cRNG *	rng,
		int	n,
		double	p
	)

Returns a random integer from the negative binomial distribution with parameters n and p, that is, the number of failures occurring before n successes in independent trials with probability p of success.

Generation is using the relationship to geometric distribution (runtime is proportional to n).

Parameters

n	n>=0
p	0<p<1
rng	the underlying random number generator

Referenced by omnetpp::bernoulli(), and cComponent::negbinomial().

poisson()

SIM_API int omnetpp::poisson	(	cRNG *	rng,
		double	lambda
	)

Returns a random integer from the Poisson distribution with parameter lambda, that is, the number of arrivals over unit time where the time between successive arrivals follow exponential distribution with parameter lambda.

Lambda is also the mean (and variance) of the distribution.

Generation method depends on value of lambda:

• 0<lambda<=30: count number of events
• lambda>30: Acceptance-Rejection due to Atkinson (see Banks, page 166)

Parameters

lambda	> 0
rng	the underlying random number generator

Referenced by omnetpp::bernoulli(), and cComponent::poisson().