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

#include "random-variable-stream.h"

Inheritance diagram for ns3::GammaRandomVariable:

Collaboration diagram for ns3::GammaRandomVariable:

Public Member Functions
	GammaRandomVariable ()
	Creates a gamma distribution RNG with the default values for alpha and beta. More...

double	GetAlpha (void) const
	Returns the alpha value for the gamma distribution returned by this RNG stream. More...

double	GetBeta (void) const
	Returns the beta value for the gamma distribution returned by this RNG stream. More...

uint32_t	GetInteger (uint32_t alpha, uint32_t beta)
	Returns a random unsigned integer from a gamma distribution with the specified alpha and beta. More...

virtual uint32_t	GetInteger (void)
	Returns a random unsigned integer from a gamma distribution with the current alpha and beta. More...

double	GetValue (double alpha, double beta)
	Returns a random double from a gamma distribution with the specified alpha and beta. More...

virtual double	GetValue (void)
	Returns a random double from a gamma distribution with the current alpha and beta. 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 this RNG stream. 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 this RNG stream. 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
	Implement the GetInstanceTypeId method defined in ObjectBase. 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 ()
	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. 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::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
static void	Cleanup (void)
	Noop. More...

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

Private Member Functions
double	GetNormalValue (double mean, double variance, double bound)
	Returns a random double from a normal distribution with the specified mean, variance, and bound. More...

Private Attributes
double	m_alpha
	The alpha value for the gamma distribution returned by this RNG stream. More...

double	m_beta
	The beta value for the gamma distribution returned by this RNG stream. More...

double	m_next
	The algorithm produces two normal values at a time. More...

bool	m_nextValid
	True if the next normal value is valid. More...

Additional Inherited Members
Protected Member Functions inherited from ns3::RandomVariableStream
RngStream *	Peek (void) const
	Get the pointer to the underlying RNG stream. 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 gamma 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 gamma distribution. It also supports the generation of single random numbers from various gamma distributions.

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

Here is an example of how to use this class:

double alpha = 5.0;
double beta = 2.0;
Ptr<GammaRandomVariable> x = CreateObject<GammaRandomVariable> ();
x->SetAttribute ("Alpha", DoubleValue (alpha));
x->SetAttribute ("Beta", DoubleValue (beta));
// The expected value for the mean of the values returned by a
// gammaly distributed random variable is equal to 
//
//     E[value]  =  alpha * beta  .
//
double value = x->GetValue ();

Config Paths

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

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

Attributes

Alpha: The alpha value for the gamma 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
Beta: The beta value for the gamma 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 88 bytes (on a 64-bit architecture).

Definition at line 1517 of file random-variable-stream.h.

Constructor & Destructor Documentation

ns3::GammaRandomVariable::GammaRandomVariable ( )

Creates a gamma distribution RNG with the default values for alpha and beta.

Definition at line 898 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

double ns3::GammaRandomVariable::GetAlpha ( void ) const

Returns the alpha value for the gamma distribution returned by this RNG stream.

Returns: The alpha value for the gamma distribution returned by this RNG stream.

Definition at line 908 of file random-variable-stream.cc.

References m_alpha, and NS_LOG_FUNCTION.

double ns3::GammaRandomVariable::GetBeta ( void ) const

Returns the beta value for the gamma distribution returned by this RNG stream.

Returns: The beta value for the gamma distribution returned by this RNG stream.

Definition at line 914 of file random-variable-stream.cc.

References m_beta, and NS_LOG_FUNCTION.

uint32_t ns3::GammaRandomVariable::GetInteger	(	uint32_t	alpha,
		uint32_t	beta
	)

Returns a random unsigned integer from a gamma distribution with the specified alpha and beta.

Parameters

[in]	alpha	Alpha value for the gamma distribution.
[in]	beta	Beta value for the gamma 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 989 of file random-variable-stream.cc.

References GetValue(), and NS_LOG_FUNCTION.

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uint32_t ns3::GammaRandomVariable::GetInteger ( void )

virtual

Returns a random unsigned integer from a gamma distribution with the current alpha and beta.

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 1002 of file random-variable-stream.cc.

References GetValue(), m_alpha, m_beta, and NS_LOG_FUNCTION.

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double ns3::GammaRandomVariable::GetNormalValue	(	double	mean,
		double	variance,
		double	bound
	)

private

Returns a random double from a normal distribution with the specified mean, variance, and bound.

Parameters

[in]	mean	Mean value for the normal distribution.
[in]	variance	Variance value for the normal distribution.
[in]	bound	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 $u1$ and $u2$ are uniform variables over [0,1], then the values that would be returned normally, $x1$ and $x2$ , are calculated as follows:

$\begin{eqnarray*} v1 & = & 2 * u1 - 1 \\ v2 & = & 2 * u2 - 1 \\ w & = & v1 * v1 + v2 * v2 \\ y & = & \sqrt{\frac{-2 * \log(w)}{w}} \\ x1 & = & mean + v1 * y * \sqrt{variance} \\ x2 & = & mean + v2 * y * \sqrt{variance} . \end{eqnarray*}$

For the antithetic case, $(1 - u1$ ) and $(1 - u2$ ) are the distances that $u1$ and $u2$ would be from $1$ . The antithetic values returned, $x1'$ and $x2'$ , are calculated as follows:

$\begin{eqnarray*} v1' & = & 2 * (1 - u1) - 1 \\ v2' & = & 2 * (1 - u2) - 1 \\ w' & = & v1' * v1' + v2' * v2' \\ y' & = & \sqrt{\frac{-2 * \log(w')}{w'}} \\ x1' & = & mean + v1' * y' * \sqrt{variance} \\ x2' & = & mean + v2' * y' * \sqrt{variance} , \end{eqnarray*}$

which now involves the distances $u1$ and $u2$ are from 1.

Definition at line 1009 of file random-variable-stream.cc.

References ns3::RandomVariableStream::IsAntithetic(), m_next, m_nextValid, NS_LOG_FUNCTION, ns3::RandomVariableStream::Peek(), ns3::RngStream::RandU01(), and visualizer.higcontainer::w.

Referenced by GetValue().

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TypeId ns3::GammaRandomVariable::GetTypeId ( void )

static

Register this type.

Returns: The object TypeId.

Definition at line 881 of file random-variable-stream.cc.

References m_alpha, m_beta, ns3::MakeDoubleAccessor(), and ns3::TypeId::SetParent().

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double ns3::GammaRandomVariable::GetValue	(	double	alpha,
		double	beta
	)

Returns a random double from a gamma distribution with the specified alpha and beta.

Parameters

[in]	alpha	Alpha value for the gamma distribution.
[in]	beta	Beta value for the gamma 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 937 of file random-variable-stream.cc.

References GetNormalValue(), GetValue(), ns3::NormalRandomVariable::INFINITE_VALUE, ns3::RandomVariableStream::IsAntithetic(), NS_LOG_FUNCTION, ns3::RandomVariableStream::Peek(), ns3::RngStream::RandU01(), and sample-rng-plot::x.

Referenced by RandomVariableStreamGammaTestCase::ChiSquaredTest(), RandomVariableStreamGammaAntitheticTestCase::ChiSquaredTest(), RandomVariableStreamGammaTestCase::DoRun(), and RandomVariableStreamGammaAntitheticTestCase::DoRun().

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double ns3::GammaRandomVariable::GetValue ( void )

virtual

Returns a random double from a gamma distribution with the current alpha and beta.

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 996 of file random-variable-stream.cc.

References m_alpha, m_beta, and NS_LOG_FUNCTION.

Referenced by GetInteger(), and GetValue().

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