The Erlang distribution Random Number Generator (RNG) that allows stream numbers to be set deterministically. More...

#include <random-variable-stream.h>

Inheritance diagram for ns3::ErlangRandomVariable:

Collaboration diagram for ns3::ErlangRandomVariable:

Public Member Functions
	ErlangRandomVariable ()
	Creates an Erlang distribution RNG with the default values for k and lambda.
uint32_t	GetInteger (uint32_t k, uint32_t lambda)
	Returns a random unsigned integer from an Erlang distribution with the specified k and lambda.
virtual uint32_t	GetInteger (void)
	Returns a random unsigned integer from an Erlang distribution with the current k and lambda.
uint32_t	GetK (void) const
	Returns the k value for the Erlang distribution returned by this RNG stream.
double	GetLambda (void) const
	Returns the lambda value for the Erlang distribution returned by this RNG stream.
double	GetValue (uint32_t k, double lambda)
	Returns a random double from an Erlang distribution with the specified k and lambda.
virtual double	GetValue (void)
	Returns a random double from an Erlang distribution with the current k and lambda.
Public Member Functions inherited from ns3::RandomVariableStream
	RandomVariableStream ()
virtual	~RandomVariableStream ()
int64_t	GetStream (void) const
	Returns the stream number for this RNG stream.
bool	IsAntithetic (void) const
	Returns true if antithetic values should be generated.
void	SetAntithetic (bool isAntithetic)
	Specifies whether antithetic values should be generated.
void	SetStream (int64_t stream)
	Specifies the stream number for this RNG stream.
Public Member Functions inherited from ns3::Object
	Object ()
virtual	~Object ()
void	AggregateObject (Ptr< Object > other)
void	Dispose (void)
AggregateIterator	GetAggregateIterator (void) const
virtual TypeId	GetInstanceTypeId (void) const
template<typename T >
Ptr< T >	GetObject (void) const
template<typename T >
Ptr< T >	GetObject (TypeId tid) const
void	Start (void)
Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount ()
	SimpleRefCount (const SimpleRefCount &o)
uint32_t	GetReferenceCount (void) const
SimpleRefCount &	operator= (const SimpleRefCount &o)
void	Ref (void) const
void	Unref (void) const
Public Member Functions inherited from ns3::ObjectBase
virtual	~ObjectBase ()
void	GetAttribute (std::string name, AttributeValue &value) const
bool	GetAttributeFailSafe (std::string name, AttributeValue &attribute) const
void	SetAttribute (std::string name, const AttributeValue &value)
bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)
bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)
bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)
bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)
bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)

Static Public Member Functions
static TypeId	GetTypeId (void)
	This method returns the TypeId associated to ns3::ErlangRandomVariable.

Private Member Functions
double	GetExponentialValue (double mean, double bound)
	Returns a random double from an exponential distribution with the specified mean and upper bound.

Private Attributes
uint32_t	m_k
	The k value for the Erlang distribution returned by this RNG stream.
double	m_lambda
	The lambda value for the Erlang distribution returned by this RNG stream.

Additional Inherited Members
Protected Member Functions inherited from ns3::RandomVariableStream
RngStream *	Peek (void) const
	Returns a pointer to the underlying RNG stream.

Detailed Description

The Erlang distribution Random Number Generator (RNG) that allows stream numbers to be set deterministically.

This class supports the creation of objects that return random numbers from a fixed Erlang distribution. It also supports the generation of single random numbers from various Erlang distributions.

The Erlang distribution is a special case of the Gamma distribution where k (= alpha) is a non-negative integer. Erlang distributed variables can be generated using a much faster algorithm than gamma variables.

The probability density function is defined over the interval [0, $+\infty$ ) as: $\frac{x^{k-1} e^{-\frac{x}{\lambda}}}{\lambda^k (k-1)!}$ where $mean = k \lambda$ and $variance = k \lambda^2$

Here is an example of how to use this class:

uint32_t k = 5;
double lambda = 2.0;
Ptr<ErlangRandomVariable> x = CreateObject<ErlangRandomVariable> ();
x->SetAttribute ("K", IntegerValue (k));
x->SetAttribute ("Lambda", DoubleValue (lambda));
// The expected value for the mean of the values returned by a
// Erlangly distributed random variable is equal to 
//
//     E[value]  =  k * lambda  .
//
double value = x->GetValue ();

Definition at line 1641 of file random-variable-stream.h.

Constructor & Destructor Documentation

ns3::ErlangRandomVariable::ErlangRandomVariable ( )

Creates an Erlang distribution RNG with the default values for k and lambda.

Definition at line 983 of file random-variable-stream.cc.

Member Function Documentation

double ns3::ErlangRandomVariable::GetExponentialValue	(	double	mean,
		double	bound
	)

private

Returns a random double from an exponential distribution with the specified mean and upper bound.

Parameters

mean	Mean value of the random variables.
bound	Upper bound on values returned.

Returns: A floating point random value.

Note that antithetic values are being generated if m_isAntithetic is equal to true. If $u$ is a uniform variable over [0,1] and

$x = - mean * \log(u)$

is a value that would be returned normally, then $(1 - u$ ) is the distance that $u$ would be from $1$ . The value returned in the antithetic case, $x'$ , is calculated as

$x' = - mean * \log(1 - u),$

which now involves the log of the distance $u$ is from the 1.

Definition at line 1045 of file random-variable-stream.cc.

References ns3::RandomVariableStream::IsAntithetic(), ns3::RandomVariableStream::Peek(), and ns3::RngStream::RandU01().

Referenced by GetValue().

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uint32_t ns3::ErlangRandomVariable::GetInteger	(	uint32_t	k,
		uint32_t	lambda
	)

Returns a random unsigned integer from an Erlang distribution with the specified k and lambda.

Parameters

k	K value for the Erlang distribution.
lambda	Lambda value for the Erlang distribution.

Returns: A random unsigned integer value.

Note that antithetic values are being generated if m_isAntithetic is equal to true. If $u$ is a uniform variable over [0,1] and $x$ is a value that would be returned normally, then $(1 - u$ ) is the distance that $u$ would be from $1$ . The value returned in the antithetic case, $x'$ , uses (1-u), which is the distance $u$ is from the 1.

Definition at line 1028 of file random-variable-stream.cc.

References GetValue().

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uint32_t ns3::ErlangRandomVariable::GetInteger ( void )

virtual

Returns a random unsigned integer from an Erlang distribution with the current k and lambda.

Returns: A random unsigned integer value.

Note that antithetic values are being generated if m_isAntithetic is equal to true. If $u$ is a uniform variable over [0,1] and $x$ is a value that would be returned normally, then $(1 - u$ ) is the distance that $u$ would be from $1$ . The value returned in the antithetic case, $x'$ , uses (1-u), which is the distance $u$ is from the 1.

Implements ns3::RandomVariableStream.

Definition at line 1039 of file random-variable-stream.cc.

References GetValue(), m_k, and m_lambda.

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uint32_t ns3::ErlangRandomVariable::GetK ( void ) const

Returns the k value for the Erlang distribution returned by this RNG stream.

Returns: The k value for the Erlang distribution returned by this RNG stream.

Definition at line 989 of file random-variable-stream.cc.

References m_k.

double ns3::ErlangRandomVariable::GetLambda ( void ) const

Returns the lambda value for the Erlang distribution returned by this RNG stream.

Returns: The lambda value for the Erlang distribution returned by this RNG stream.

Definition at line 994 of file random-variable-stream.cc.

References m_lambda.

TypeId ns3::ErlangRandomVariable::GetTypeId ( void )

static

This method returns the TypeId associated to ns3::ErlangRandomVariable.

This object is accessible through the following paths with Config::Set and Config::Connect:

/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanDirection/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanPitch/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanVelocity/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Pause/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Speed/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Direction/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Speed/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Pause/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/X/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/Y/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/Z/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomDiscPositionAllocator/Rho/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomDiscPositionAllocator/Theta/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomRectanglePositionAllocator/X/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomRectanglePositionAllocator/Y/$ns3::ErlangRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Speed/$ns3::ErlangRandomVariable
/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OffTime/$ns3::ErlangRandomVariable
/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OnTime/$ns3::ErlangRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::CsmaNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::PointToPointNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::SimpleNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationDelayModel/$ns3::RandomPropagationDelayModel/Variable/$ns3::ErlangRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv
/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable

Attributes defined for this type:

K: The k value for the Erlang distribution returned by this RNG stream.
- Set with class: ns3::IntegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 1
- Flags: construct write read
Lambda: The lambda value for the Erlang distribution returned by this RNG stream.
- Set with class: ns3::DoubleValue
- Underlying type: double -1.79769e+308:1.79769e+308
- Initial value: 1
- Flags: construct write read

Attributes defined in parent class ns3::RandomVariableStream:

Stream: The stream number for this RNG stream. -1 means "allocate a stream automatically". Note that if -1 is set, Get will return -1 so that it is not possible to know which value was automatically allocated.
- Set with class: ns3::IntegerValue
- Underlying type: int64_t -9223372036854775808:9223372036854775807
- Initial value: -1
- Flags: construct write read
Antithetic: Set this RNG stream to generate antithetic values
- Set with class: BooleanValue
- Underlying type: bool
- Initial value: false
- Flags: construct write read

No TraceSources defined for this type.

Reimplemented from ns3::RandomVariableStream.

Definition at line 967 of file random-variable-stream.cc.

References m_k, m_lambda, and ns3::TypeId::SetParent().

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double ns3::ErlangRandomVariable::GetValue	(	uint32_t	k,
		double	lambda
	)

Returns a random double from an Erlang distribution with the specified k and lambda.

Parameters

k	K value for the Erlang distribution.
lambda	Lambda value for the Erlang distribution.

Returns: A floating point random value.

Note that antithetic values are being generated if m_isAntithetic is equal to true. If $u$ is a uniform variable over [0,1] and $x$ is a value that would be returned normally, then $(1 - u$ ) is the distance that $u$ would be from $1$ . The value returned in the antithetic case, $x'$ , uses (1-u), which is the distance $u$ is from the 1.

Definition at line 1012 of file random-variable-stream.cc.

References GetExponentialValue().

Referenced by RandomVariableStreamErlangTestCase::ChiSquaredTest(), RandomVariableStreamErlangAntitheticTestCase::ChiSquaredTest(), ns3::NakagamiPropagationLossModel::DoCalcRxPower(), RandomVariableStreamErlangTestCase::DoRun(), and RandomVariableStreamErlangAntitheticTestCase::DoRun().

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double ns3::ErlangRandomVariable::GetValue ( void )

virtual

Returns a random double from an Erlang distribution with the current k and lambda.

Returns: A floating point random value.

Note that antithetic values are being generated if m_isAntithetic is equal to true. If $u$ is a uniform variable over [0,1] and $x$ is a value that would be returned normally, then $(1 - u$ ) is the distance that $u$ would be from $1$ . The value returned in the antithetic case, $x'$ , uses (1-u), which is the distance $u$ is from the 1.

Note that we have to re-implement this method here because the method is overloaded above for the two-argument variant and the c++ name resolution rules don't work well with overloads split between parent and child classes.

Implements ns3::RandomVariableStream.

Definition at line 1034 of file random-variable-stream.cc.

References m_k, and m_lambda.

Referenced by GetInteger().

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