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

#include <random-variable-stream.h>

Inheritance diagram for ns3::ExponentialRandomVariable:

Collaboration diagram for ns3::ExponentialRandomVariable:

Public Member Functions
	ExponentialRandomVariable ()
	Creates a exponential distribution RNG with the default values for the mean and upper bound. More...

double	GetBound (void) const
	Returns the upper bound on values that can be returned by this RNG stream. More...

uint32_t	GetInteger (uint32_t mean, uint32_t bound)
	Returns a random unsigned integer from an exponential distribution with the specified mean and upper bound. More...

virtual uint32_t	GetInteger (void)
	Returns a random unsigned integer from an exponential distribution with the current mean and upper bound. More...

double	GetMean (void) const
	Returns the mean value of the random variables returned by this RNG stream. More...

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

virtual double	GetValue (void)
	Returns a random double from an exponential distribution with the current mean and upper bound. More...

Public Member Functions inherited from ns3::RandomVariableStream
	RandomVariableStream ()

virtual	~RandomVariableStream ()

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

bool	IsAntithetic (void) const
	Returns true if antithetic values should be generated. More...

void	SetAntithetic (bool isAntithetic)
	Specifies 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. More...

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

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 Attributes
double	m_bound
	The upper bound on values that can be returned by this RNG stream. More...

double	m_mean
	The mean value of the random variables returned by this RNG stream. More...

Additional Inherited Members
Protected Member Functions inherited from ns3::RandomVariableStream
RngStream *	Peek (void) const
	Returns a 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 exponential 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 exponential distribution. It also supports the generation of single random numbers from various exponential distributions.

The probability density function of an exponential variable is defined over the interval [0, $+\infty$ ) as: $\alpha e^{-\alpha x}$ where $\alpha = \frac{1}{mean}$

Since exponential distributions can theoretically return unbounded values, it is sometimes useful to specify a fixed upper limit. The bounded version is defined over the interval [0,b] as: $\alpha e^{-\alpha x} \quad x \in [0,b]$ . Note that in this case the true mean of the distribution is slightly smaller than the mean value specified: $1/\alpha - b/(e^{\alpha \, b}-1)$ .

Here is an example of how to use this class:

double mean = 3.14;
double bound = 0.0;
Ptr<ExponentialRandomVariable> x = CreateObject<ExponentialRandomVariable> ();
x->SetAttribute ("Mean", DoubleValue (mean));
x->SetAttribute ("Bound", DoubleValue (bound));
// The expected value for the mean of the values returned by an
// exponentially distributed random variable is equal to mean.
double value = x->GetValue ();

Config Paths

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

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

Attributes

Mean: The mean of the values 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
Bound: The upper bound on the values returned by this RNG stream.
- Set with class: ns3::DoubleValue
- Underlying type: double -1.79769e+308:1.79769e+308
- Initial value: 0
- 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 474 of file random-variable-stream.h.

Constructor & Destructor Documentation

ns3::ExponentialRandomVariable::ExponentialRandomVariable ( )

Creates a exponential distribution RNG with the default values for the mean and upper bound.

Definition at line 386 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

double ns3::ExponentialRandomVariable::GetBound ( void ) const

Returns the upper bound on values that can be returned by this RNG stream.

Returns: The upper bound on values that can be returned by this RNG stream.

Definition at line 399 of file random-variable-stream.cc.

References m_bound, and NS_LOG_FUNCTION.

uint32_t ns3::ExponentialRandomVariable::GetInteger	(	uint32_t	mean,
		uint32_t	bound
	)

Returns a random unsigned integer 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 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

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

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 429 of file random-variable-stream.cc.

References GetValue(), and NS_LOG_FUNCTION.

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uint32_t ns3::ExponentialRandomVariable::GetInteger ( void )

virtual

Returns a random unsigned integer from an exponential distribution with the current mean and upper bound.

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

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

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.

Implements ns3::RandomVariableStream.

Definition at line 442 of file random-variable-stream.cc.

References GetValue(), m_bound, m_mean, and NS_LOG_FUNCTION.

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double ns3::ExponentialRandomVariable::GetMean ( void ) const

Returns the mean value of the random variables returned by this RNG stream.

Returns: The mean value of the random variables returned by this RNG stream.

Definition at line 393 of file random-variable-stream.cc.

References m_mean, and NS_LOG_FUNCTION.

TypeId ns3::ExponentialRandomVariable::GetTypeId ( void )

static

Definition at line 369 of file random-variable-stream.cc.

References m_bound, m_mean, ns3::MakeDoubleAccessor(), and ns3::TypeId::SetParent().

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double ns3::ExponentialRandomVariable::GetValue	(	double	mean,
		double	bound
	)

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 406 of file random-variable-stream.cc.

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

Referenced by ns3::UanMacRc::Associate(), ns3::UanMacRc::AssociateTimeout(), RngExponentialTestCase::ChiSquaredTest(), RandomVariableStreamExponentialTestCase::ChiSquaredTest(), RandomVariableStreamExponentialAntitheticTestCase::ChiSquaredTest(), RandomVariableStreamExponentialTestCase::DoRun(), RandomVariableStreamExponentialAntitheticTestCase::DoRun(), ns3::UanMacRc::RtsTimeout(), ns3::UanMacRc::ScheduleData(), Experiment::SendMultiDestinations(), and ns3::UanMacRc::SendRts().

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double ns3::ExponentialRandomVariable::GetValue ( void )

virtual

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

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.

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 436 of file random-variable-stream.cc.

References m_bound, m_mean, and NS_LOG_FUNCTION.

Referenced by GetInteger().

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