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

#include "random-variable-stream.h"

Inheritance diagram for ns3::WeibullRandomVariable:

Collaboration diagram for ns3::WeibullRandomVariable:

Public Member Functions
	WeibullRandomVariable ()
	Creates a Weibull distribution RNG with the default values for the scale, shape, and upper bound.

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

virtual uint32_t	GetInteger ()
	Get the next random value drawn from the distribution.

uint32_t	GetInteger (uint32_t scale, uint32_t shape, uint32_t bound)
	Get the next random value drawn from the distribution.

double	GetMean () const
	Returns the mean value for the Weibull distribution returned by this RNG stream.

double	GetScale () const
	Returns the scale parameter for the Weibull distribution returned by this RNG stream.

double	GetShape () const
	Returns the shape parameter for the Weibull distribution returned by this RNG stream.

double	GetValue () override
	Get the next random value drawn from the distribution.

double	GetValue (double scale, double shape, double bound)
	Get the next random value drawn from the distribution.

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

	RandomVariableStream (const RandomVariableStream &)=delete

	~RandomVariableStream () override
	Destructor.

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

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

RandomVariableStream &	operator= (const RandomVariableStream &)=delete

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

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

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

	~Object () override
	Destructor.

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

void	Dispose ()
	Dispose of this Object.

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

TypeId	GetInstanceTypeId () const override
	Get the most derived TypeId for this Object.

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

template<>
Ptr< Object >	GetObject () const
	Specialization of () for objects of type ns3::Object.

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

template<>
Ptr< Object >	GetObject (TypeId tid) const
	Specialization of (TypeId tid) for objects of type ns3::Object.

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

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

void	UnidirectionalAggregateObject (Ptr< Object > other)
	Aggregate an Object to another Object.

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

	SimpleRefCount (const SimpleRefCount &o)
	Copy constructor.

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

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

void	Ref () const
	Increment the reference count.

void	Unref () const
	Decrement the reference count.

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

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

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

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

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

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

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

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

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

Static Public Member Functions
static double	GetMean (double scale, double shape)
	Returns the mean value for the Weibull distribution returned by this RNG stream.

static TypeId	GetTypeId ()
	Register this type.

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

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

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

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

double	m_scale
	The scale parameter for the Weibull distribution returned by this RNG stream.

double	m_shape
	The shape parameter for the Weibull distribution returned by this RNG stream.

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

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

virtual void	DoDispose ()
	Destructor implementation.

virtual void	DoInitialize ()
	Initialize() implementation.

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

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

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

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

Detailed Description

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

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

The probability density function is:

$P(x; \lambda, k) dx = \frac{k}{\lambda} \\ \left(\frac{x}{\lambda}\right)^{k-1} \\ e^{-\left(\frac{x}{\lambda}\right)^k} dx, \\ \quad x \in [0, +\infty)$

where is the Shape parameter and $\lambda > 0$ is the Scale parameter.

The mean $\mu$ is related to the Scale and Shape parameters by the following relation:

$\mu = \lambda\Gamma\left(1+\frac{1}{k}\right)$

where $\Gamma$ is the Gamma function.

The variance of the distribution is

$\sigma^2 = \lambda^2 \left[ \Gamma\left(1 + \frac{2}{k}\right) - \\ \left( \Gamma\left(1 + \frac{1}{k}\right)\right)^2 \right]$

For the mean rapidly approaches just $\lambda$ , with variance

$\sigma^2 \approx \frac{\pi^2}{6 k^2} + \mathcal{O}(k^{-3})$

The Weibull RNG value is generated by

$x = \lambda {(-\log(u))}^{\frac{1}{k}}$

where is a uniform random variable on [0,1).

Bounded Distribution

Since Weibull distributions can theoretically return unbounded values, it is sometimes useful to specify a fixed upper limit. The bounded version is defined over the interval $x \in [0, b]$ . Note however when the upper limit is specified, the mean of the resulting distribution is slightly smaller than the mean value in the unbounded case.

Example

Here is an example of how to use this class:

double scale = 5.0;
double shape = 1.0;
 
Ptr<WeibullRandomVariable> x = CreateObject<WeibullRandomVariable> ();
x->SetAttribute ("Scale", DoubleValue (scale));
x->SetAttribute ("Shape", DoubleValue (shape));
 
double value = x->GetValue ();

Antithetic Values.

If an instance of this RNG is configured to return antithetic values, the actual value returned, , is generated as follows:

$x' = \lambda {(-\log(1 - u))}^{\frac{1}{k}} ,$

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

Definition at line 821 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ WeibullRandomVariable()

ns3::WeibullRandomVariable::WeibullRandomVariable ( )

Creates a Weibull distribution RNG with the default values for the scale, shape, and upper bound.

Definition at line 572 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ GetBound()

double ns3::WeibullRandomVariable::GetBound ( ) 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 592 of file random-variable-stream.cc.

References m_bound.

◆ GetInteger() [1/2]

uint32_t ns3::RandomVariableStream::GetInteger ( )

virtual

Get the next random value drawn from the distribution.

Returns: A random value.

Reimplemented from ns3::RandomVariableStream.

Definition at line 144 of file random-variable-stream.cc.

◆ GetInteger() [2/2]

uint32_t ns3::WeibullRandomVariable::GetInteger	(	uint32_t	scale,
		uint32_t	shape,
		uint32_t	bound )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	scale	Scale parameter for the Weibull distribution.
[in]	shape	Shape parameter for the Weibull distribution.
[in]	bound	Upper bound on values returned.

Definition at line 638 of file random-variable-stream.cc.

References ns3::RandomVariableStream::GetStream(), GetValue(), and NS_LOG_DEBUG.

Here is the call graph for this function:

◆ GetMean() [1/2]

double ns3::WeibullRandomVariable::GetMean ( ) const

Returns the mean value for the Weibull distribution returned by this RNG stream.

Returns: The mean value for the Weibull distribution returned by this RNG stream.

Definition at line 605 of file random-variable-stream.cc.

References GetMean(), m_scale, m_shape, and NS_LOG_FUNCTION.

Referenced by GetMean().

Here is the call graph for this function:

Here is the caller graph for this function:

◆ GetMean() [2/2]

double ns3::WeibullRandomVariable::GetMean	(	double	scale,
		double	shape )

static

Returns the mean value for the Weibull distribution returned by this RNG stream.

Returns: The mean value for the Weibull distribution returned by this RNG stream.

Parameters

[in]	scale	Scale parameter for the Weibull distribution.
[in]	shape	Shape parameter for the Weibull distribution.

Definition at line 598 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

◆ GetScale()

double ns3::WeibullRandomVariable::GetScale ( ) const

Returns the scale parameter for the Weibull distribution returned by this RNG stream.

Returns: The scale parameter for the Weibull distribution returned by this RNG stream.

Definition at line 580 of file random-variable-stream.cc.

References m_scale.

◆ GetShape()

double ns3::WeibullRandomVariable::GetShape ( ) const

Returns the shape parameter for the Weibull distribution returned by this RNG stream.

Returns: The shape parameter for the Weibull distribution returned by this RNG stream.

Definition at line 586 of file random-variable-stream.cc.

References m_shape.

◆ GetTypeId()

TypeId ns3::WeibullRandomVariable::GetTypeId ( )

static

Register this type.

Returns: The object TypeId.

Definition at line 545 of file random-variable-stream.cc.

References m_bound, m_scale, m_shape, ns3::MakeDoubleAccessor(), ns3::MakeDoubleChecker(), and ns3::TypeId::SetParent().

Here is the call graph for this function:

◆ GetValue() [1/2]

double ns3::WeibullRandomVariable::GetValue ( )

overridevirtual

Get the next random value drawn from the distribution.

Returns: A random value.

Implements ns3::RandomVariableStream.

Definition at line 647 of file random-variable-stream.cc.

References GetValue(), m_bound, m_scale, m_shape, and NS_LOG_FUNCTION.

Referenced by GetInteger(), and GetValue().

Here is the call graph for this function:

Here is the caller graph for this function:

◆ GetValue() [2/2]

double ns3::WeibullRandomVariable::GetValue	(	double	scale,
		double	shape,
		double	bound )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	scale	Scale parameter for the Weibull distribution.
[in]	shape	Shape parameter for the Weibull distribution.
[in]	bound	Upper bound on values returned.

Definition at line 612 of file random-variable-stream.cc.

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

Here is the call graph for this function:

Member Data Documentation

◆ m_bound

double ns3::WeibullRandomVariable::m_bound

private

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

Definition at line 890 of file random-variable-stream.h.

Referenced by GetBound(), GetTypeId(), and GetValue().

◆ m_scale

double ns3::WeibullRandomVariable::m_scale

private

The scale parameter for the Weibull distribution returned by this RNG stream.

Definition at line 884 of file random-variable-stream.h.

Referenced by GetMean(), GetScale(), GetTypeId(), and GetValue().

◆ m_shape

double ns3::WeibullRandomVariable::m_shape

private

The shape parameter for the Weibull distribution returned by this RNG stream.

Definition at line 887 of file random-variable-stream.h.

Referenced by GetMean(), GetShape(), GetTypeId(), and GetValue().

The documentation for this class was generated from the following files:

src/core/model/random-variable-stream.h
src/core/model/random-variable-stream.cc

Public Member Functions

Static Public Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ WeibullRandomVariable()

Member Function Documentation

◆ GetBound()

◆ GetInteger() [1/2]

◆ GetInteger() [2/2]

◆ GetMean() [1/2]

◆ GetMean() [2/2]

◆ GetScale()

◆ GetShape()

◆ GetTypeId()

◆ GetValue() [1/2]

◆ GetValue() [2/2]

Member Data Documentation

◆ m_bound

◆ m_scale

◆ m_shape