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

#include "random-variable-stream.h"

Inheritance diagram for ns3::LogNormalRandomVariable:

Collaboration diagram for ns3::LogNormalRandomVariable:

Public Member Functions
	LogNormalRandomVariable ()
	Creates a log-normal distribution RNG with the default values for mu and sigma.

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

uint32_t	GetInteger (uint32_t mu, uint32_t sigma)
	Get the next random value drawn from the distribution.

double	GetMu () const
	Returns the mu value for the log-normal distribution returned by this RNG stream.

double	GetSigma () const
	Returns the sigma value for the log-normal distribution returned by this RNG stream.

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

double	GetValue (double mu, double sigma)
	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 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_mu
	The mu value for the log-normal distribution returned by this RNG stream.

bool	m_nextValid
	True if m_normal is valid.

double	m_normal
	The algorithm produces two values at a time.

double	m_sigma
	The sigma value for the log-normal distribution returned by this RNG stream.

double	m_v2
	The algorithm produces two values at a time.

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 log-normal 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 log-normal distribution. It also supports the generation of single random numbers from various log-normal distributions. If one takes the natural logarithm of a random variable following the log-normal distribution, the obtained values follow a normal distribution.

The probability density function is defined using two parameters Mu = $\mu$ and Sigma = $\sigma$ as:

$P(x; \mu, \sigma) dx = \frac{1}{x\sqrt{2\pi\sigma^2}} e^{-\frac{(ln(x) - \mu)^2}{2\sigma^2}} dx, \\ \quad x \in [0, +\infty)$

The distribution has mean value

$\langle x | P(x; \mu, \sigma) \rangle = e^{\mu+\frac{\sigma^2}{2}}$

and variance

$var(x) = (e^{\sigma^2}-1)e^{2\mu+\sigma^2}$

Note these are the mean and variance of the log-normal distribution, not the Mu or Sigma configuration variables.

If the desired mean and variance are known the $\mu$ and $\sigma$ parameters can be calculated instead with the following equations:

$\mu = ln(\langle x \rangle) - \\ \frac{1}{2}ln\left(1+\frac{var(x)}{{\langle x \rangle}^2}\right)$

and

$\sigma^2 = ln\left(1+\frac{var(x)}{{\langle x \rangle}^2}\right)$

If , are uniform variables over [0,1] then the log-normal RNG value, is generated as follows:

$\begin{eqnarray*} v_1 & = & 2 u_1 - 1 \\ v_2 & = & 2 u_2 - 1 \\ r^2 & = & v_1^2 + v_2^2 \\ y & = & \sqrt{\frac{-2 \log{r^2}}{r^2}} \\ x & = & \exp\left(\mu + v_1 y \sigma\right) . \end{eqnarray*}$

Example

Here is an example of how to use this class:

double mu = 5.0;
double sigma = 2.0;
 
Ptr<LogNormalRandomVariable> x = CreateObject<LogNormalRandomVariable> ();
x->SetAttribute ("Mu", DoubleValue (mu));
x->SetAttribute ("Sigma", DoubleValue (sigma));
 
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:

$\begin{eqnarray*} v_1^{\prime} & = & 2 (1 - u_1) - 1 \\ v_2^{\prime} & = & 2 (1 - u_2) - 1 \\ r^{\prime 2} & = & v_1^{\prime 2} + v_2^{\prime 2} \\ y^{\prime} & = & v_1^{\prime}\sqrt{\frac{-2 \log(r^{\prime 2})}{r^{\prime 2}}} \\ x^{\prime} & = & \exp\left(\mu + y^{\prime} \sigma\right) . \end{eqnarray*}$

which now involves the distances and are from 1.

Definition at line 1134 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ LogNormalRandomVariable()

ns3::LogNormalRandomVariable::LogNormalRandomVariable ( )

Creates a log-normal distribution RNG with the default values for mu and sigma.

Definition at line 806 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ 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::LogNormalRandomVariable::GetInteger	(	uint32_t	mu,
		uint32_t	sigma )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	mu	Mu value for the log-normal distribution.
[in]	sigma	Sigma value for the log-normal distribution.

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

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

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◆ GetMu()

double ns3::LogNormalRandomVariable::GetMu ( ) const

Returns the mu value for the log-normal distribution returned by this RNG stream.

Returns: The mu value for the log-normal distribution returned by this RNG stream.

Definition at line 815 of file random-variable-stream.cc.

References m_mu.

◆ GetSigma()

double ns3::LogNormalRandomVariable::GetSigma ( ) const

Returns the sigma value for the log-normal distribution returned by this RNG stream.

Returns: The sigma value for the log-normal distribution returned by this RNG stream.

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

References m_sigma.

◆ GetTypeId()

TypeId ns3::LogNormalRandomVariable::GetTypeId ( )

static

Register this type.

Returns: The object TypeId.

Definition at line 784 of file random-variable-stream.cc.

References m_mu, m_sigma, ns3::MakeDoubleAccessor(), ns3::MakeDoubleChecker(), and ns3::TypeId::SetParent().

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◆ GetValue() [1/2]

double ns3::LogNormalRandomVariable::GetValue ( )

overridevirtual

Get the next random value drawn from the distribution.

Returns: A random value.

Implements ns3::RandomVariableStream.

Definition at line 899 of file random-variable-stream.cc.

References GetValue(), m_mu, and m_sigma.

Referenced by GetInteger(), and GetValue().

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◆ GetValue() [2/2]

double ns3::LogNormalRandomVariable::GetValue	(	double	mu,
		double	sigma )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	mu	Mu value for the log-normal distribution.
[in]	sigma	Sigma value for the log-normal distribution.

Definition at line 841 of file random-variable-stream.cc.

References ns3::RandomVariableStream::GetStream(), ns3::RandomVariableStream::IsAntithetic(), m_nextValid, m_normal, m_v2, ns3::normal, NS_LOG_DEBUG, ns3::RandomVariableStream::Peek(), and ns3::RngStream::RandU01().

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Member Data Documentation

◆ m_mu

double ns3::LogNormalRandomVariable::m_mu

private

The mu value for the log-normal distribution returned by this RNG stream.

Definition at line 1177 of file random-variable-stream.h.

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

◆ m_nextValid

bool ns3::LogNormalRandomVariable::m_nextValid

private

True if m_normal is valid.

Definition at line 1183 of file random-variable-stream.h.

Referenced by GetValue().

◆ m_normal

double ns3::LogNormalRandomVariable::m_normal

private

The algorithm produces two values at a time.

Cache parameters for possible reuse.

Definition at line 1189 of file random-variable-stream.h.

Referenced by GetValue().

◆ m_sigma

double ns3::LogNormalRandomVariable::m_sigma

private

The sigma value for the log-normal distribution returned by this RNG stream.

Definition at line 1180 of file random-variable-stream.h.

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

◆ m_v2

double ns3::LogNormalRandomVariable::m_v2

private

The algorithm produces two values at a time.

Cache parameters for possible reuse.

Definition at line 1186 of file random-variable-stream.h.

Referenced by 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

◆ LogNormalRandomVariable()

Member Function Documentation

◆ GetInteger() [1/2]

◆ GetInteger() [2/2]

◆ GetMu()

◆ GetSigma()

◆ GetTypeId()

◆ GetValue() [1/2]

◆ GetValue() [2/2]

Member Data Documentation

◆ m_mu

◆ m_nextValid

◆ m_normal

◆ m_sigma

◆ m_v2