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:

Public Member Functions
	ErlangRandomVariable ()
	Creates an Erlang distribution RNG with the default values for k and lambda. More...

uint32_t	GetInteger (uint32_t k, uint32_t lambda)
	Returns a random unsigned integer from an Erlang distribution with the specified k and lambda. More...

virtual uint32_t	GetInteger (void)
	Returns a random unsigned integer from an Erlang distribution with the current k and lambda. More...

uint32_t	GetK (void) const
	Returns the k value for the Erlang distribution returned by this RNG stream. More...

double	GetLambda (void) const
	Returns the lambda value for the Erlang distribution returned by this RNG stream. More...

double	GetValue (uint32_t k, double lambda)
	Returns a random double from an Erlang distribution with the specified k and lambda. More...

virtual double	GetValue (void)
	Returns a random double from an Erlang distribution with the current k and lambda. More...

Public Member Functions inherited from ns3::RandomVariableStream
	RandomVariableStream ()
	Default constructor. More...

virtual	~RandomVariableStream ()
	Destructor. More...

int64_t	GetStream (void) const
	Returns the stream number for the RngStream. More...

bool	IsAntithetic (void) const
	Check if antithetic values will be generated. More...

void	SetAntithetic (bool isAntithetic)
	Specify whether antithetic values should be generated. More...

void	SetStream (int64_t stream)
	Specifies the stream number for the RngStream. More...

Public Member Functions inherited from ns3::Object
	Object ()
	Constructor. More...

virtual	~Object ()
	Destructor. More...

void	AggregateObject (Ptr< Object > other)
	Aggregate two Objects together. More...

void	Dispose (void)
	Dispose of this Object. More...

AggregateIterator	GetAggregateIterator (void) const
	Get an iterator to the Objects aggregated to this one. More...

virtual TypeId	GetInstanceTypeId (void) const
	Get the most derived TypeId for this Object. More...

template<typename T >
Ptr< T >	GetObject (void) const
	Get a pointer to the requested aggregated Object. More...

template<typename T >
Ptr< T >	GetObject (TypeId tid) const
	Get a pointer to the requested aggregated Object by TypeId. More...

void	Initialize (void)
	Invoke DoInitialize on all Objects aggregated to this one. More...

bool	IsInitialized (void) const
	Check if the object has been initialized. More...

Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount ()
	Default constructor. More...

	SimpleRefCount (const SimpleRefCount &o)
	Copy constructor. More...

uint32_t	GetReferenceCount (void) const
	Get the reference count of the object. More...

SimpleRefCount &	operator= (const SimpleRefCount &o)
	Assignment operator. More...

void	Ref (void) const
	Increment the reference count. More...

void	Unref (void) const
	Decrement the reference count. More...

Public Member Functions inherited from ns3::ObjectBase
virtual	~ObjectBase ()
	Virtual destructor. More...

void	GetAttribute (std::string name, AttributeValue &value) const
	Get the value of an attribute, raising fatal errors if unsuccessful. More...

bool	GetAttributeFailSafe (std::string name, AttributeValue &value) const
	Get the value of an attribute without raising erros. More...

void	SetAttribute (std::string name, const AttributeValue &value)
	Set a single attribute, raising fatal errors if unsuccessful. More...

bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)
	Set a single attribute without raising errors. More...

bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)
	Connect a TraceSource to a Callback with a context. More...

bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)
	Connect a TraceSource to a Callback without a context. More...

bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected with a context. More...

bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected without a context. More...

Static Public Member Functions
static TypeId	GetTypeId (void)
	Register this type. More...

Static Public Member Functions inherited from ns3::RandomVariableStream
static TypeId	GetTypeId (void)
	Register this type. More...

Static Public Member Functions inherited from ns3::Object
static TypeId	GetTypeId (void)
	Register this type. More...

Static Public Member Functions inherited from ns3::ObjectBase
static TypeId	GetTypeId (void)
	Get the type ID. More...

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

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

double	m_lambda
	The lambda value for the Erlang distribution returned by this RNG stream. More...

Additional Inherited Members
Protected Member Functions inherited from ns3::RandomVariableStream
RngStream *	Peek (void) const
	Get the pointer to the underlying RngStream. More...

Protected Member Functions inherited from ns3::Object
	Object (const Object &o)
	Copy an Object. More...

virtual void	DoDispose (void)
	Destructor implementation. More...

virtual void	DoInitialize (void)
	Initialize() implementation. More...

virtual void	NotifyNewAggregate (void)
	Notify all Objects aggregated to this one of a new Object being aggregated. More...

Protected Member Functions inherited from ns3::ObjectBase
void	ConstructSelf (const AttributeConstructionList &attributes)
	Complete construction of ObjectBase; invoked by derived classes. More...

virtual void	NotifyConstructionCompleted (void)
	Notifier called once the ObjectBase is fully constructed. More...

Related Functions inherited from ns3::ObjectBase
static TypeId	GetObjectIid (void)
	Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly. More...

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 ();

Config Paths

ns3::ErlangRandomVariable is accessible through the following paths with Config::Set and Config::Connect:

"/NodeList/[i]/DeviceList/[i]/$ns3::SimpleNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::SimpleNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstStart/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::SimpleNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstSize/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::SpectrumChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::SpectrumChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationDelayModel/$ns3::RandomPropagationDelayModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::PointToPointNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::PointToPointNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstStart/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::PointToPointNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstSize/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::CsmaNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::CsmaNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstStart/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::CsmaNetDevice/ReceiveErrorModel/$ns3::BurstErrorModel/BurstSize/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::LrWpanNetDevice/Channel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::LrWpanNetDevice/Channel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/NodeList/[i]/DeviceList/[i]/$ns3::WaveNetDevice/Channel/$ns3::SpectrumChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::WaveNetDevice/Channel/$ns3::SpectrumChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/NodeList/[i]/DeviceList/[i]/$ns3::WaveNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/DeviceList/[i]/$ns3::WaveNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/NodeList/[i]/DeviceList/[i]/$ns3::WaveNetDevice/Channel/$ns3::YansWifiChannel/PropagationDelayModel/$ns3::RandomPropagationDelayModel/Variable/$ns3::ErlangRandomVariable"
"/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OnTime/$ns3::ErlangRandomVariable"
"/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OffTime/$ns3::ErlangRandomVariable"
"/NodeList/[i]/ApplicationList/[i]/$ns3::DhcpClient/Transactions/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanVelocity/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanDirection/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanPitch/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Speed/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Pause/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Direction/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Speed/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Speed/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Pause/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$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/$ns3::RandomWaypointMobilityModel/PositionAllocator/$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/Theta/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomDiscPositionAllocator/Rho/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::OutdoorPositionAllocator/X/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::OutdoorPositionAllocator/Y/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::OutdoorPositionAllocator/Z/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::ArpL3Protocol/RequestJitter/$ns3::ErlangRandomVariable"
"/NodeList/[i]/$ns3::Icmpv6L4Protocol/SolicitationJitter/$ns3::ErlangRandomVariable"
"/ChannelList/[i]/$ns3::SpectrumChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/ChannelList/[i]/$ns3::SpectrumChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/ChannelList/[i]/$ns3::YansWifiChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ErlangRandomVariable"
"/ChannelList/[i]/$ns3::YansWifiChannel/PropagationLossModel/$ns3::NakagamiPropagationLossModel/ErlangRv"
"/ChannelList/[i]/$ns3::YansWifiChannel/PropagationDelayModel/$ns3::RandomPropagationDelayModel/Variable/$ns3::ErlangRandomVariable"

Attributes

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 are defined for this type.
Size of this type is 72 bytes (on a 64-bit architecture).

Definition at line 1685 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ ErlangRandomVariable()

ns3::ErlangRandomVariable::ErlangRandomVariable ( )

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

Definition at line 1098 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ GetExponentialValue()

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

[in]	mean	Mean value of the random variables.
[in]	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 1167 of file random-variable-stream.cc.

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

Referenced by GetValue().

◆ GetInteger() [1/2]

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

[in]	k	K value for the Erlang distribution.
[in]	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 1147 of file random-variable-stream.cc.

References GetValue(), and NS_LOG_FUNCTION.

◆ GetInteger() [2/2]

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 1160 of file random-variable-stream.cc.

References GetValue(), m_k, m_lambda, and NS_LOG_FUNCTION.

◆ GetK()

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 1105 of file random-variable-stream.cc.

References m_k, and NS_LOG_FUNCTION.

◆ GetLambda()

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 1111 of file random-variable-stream.cc.

References m_lambda, and NS_LOG_FUNCTION.

◆ GetTypeId()

TypeId ns3::ErlangRandomVariable::GetTypeId ( void )

static

Register this type.

Returns: The object TypeId.

Definition at line 1081 of file random-variable-stream.cc.

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

◆ GetValue() [1/2]

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

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

Parameters

[in]	k	K value for the Erlang distribution.
[in]	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 1130 of file random-variable-stream.cc.

References GetExponentialValue(), and NS_LOG_FUNCTION.

◆ GetValue() [2/2]

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 1154 of file random-variable-stream.cc.

References m_k, m_lambda, and NS_LOG_FUNCTION.

Referenced by GetInteger().