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

#include "random-variable-stream.h"

Inheritance diagram for ns3::NormalRandomVariable:

Collaboration diagram for ns3::NormalRandomVariable:

Public Member Functions
	NormalRandomVariable ()
	Creates a normal distribution RNG with the default values for the mean, variance, and bound.

double	GetBound () const
	Returns the 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 mean, uint32_t variance, uint32_t bound)
	Get the next random value drawn from the distribution.

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

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

double	GetValue (double mean, double variance, double bound=NormalRandomVariable::INFINITE_VALUE)
	Get the next random value drawn from the distribution.

double	GetVariance () const
	Returns the variance value for the normal distribution returned by this RNG stream.

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.

Static Public Attributes
static const double	INFINITE_VALUE = 1e307
	Large constant to bound the range.

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

double	m_mean
	The mean value for the normal distribution returned by this RNG stream.

bool	m_nextValid
	True if the next value is valid.

double	m_v2
	The algorithm produces two values at a time.

double	m_variance
	The variance value for the normal distribution returned by this RNG stream.

double	m_y
	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 normal (Gaussian) 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 normal distribution. It also supports the generation of single random numbers from various normal distributions.

The probability density function is:

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

where the Mean is given by $\mu$ and the Variance is $\sigma^2$

If , are uniform variables over [0,1] then the Gaussian RNG values, and , are calculated as follows:

$\begin{eqnarray*} v_1 & = & 2 u_1 - 1 \\ v_2 & = & 2 u_2 - 1 \\ r^2 & = & v_1^2 + v_2^2 \\ y & = & \sqrt{\frac{-2 \log(r^2)}{r^2}} \\ x_1 & = & \mu + v_1 y \sqrt{\sigma^2} \\ x_2 & = & \mu + v_2 y \sqrt{\sigma^2} . \end{eqnarray*}$

Note this algorithm consumes two uniform random values and produces two normally distributed values. The implementation used here caches and to generate on the next call.

Bounded Distribution

Since normal distributions can theoretically return unbounded values, it is sometimes useful to specify a fixed bound. The NormalRandomVariable is bounded symmetrically about the mean by the Bound parameter, , i.e. its values are confined to the interval $[\mu - b, \mu + b]$ . This preserves the mean but decreases the variance.

Example

Here is an example of how to use this class:

double mean = 5.0;
double variance = 2.0;
 
Ptr<NormalRandomVariable> x = CreateObject<NormalRandomVariable> ();
x->SetAttribute ("Mean", DoubleValue (mean));
x->SetAttribute ("Variance", DoubleValue (variance));
 
// The expected value for the mean of the values returned by a
// normally distributed random variable is equal to mean.
double value = x->GetValue ();

Antithetic Values.

If an instance of this RNG is configured to return antithetic values, the actual values returned, $x_1^{\prime}$ and $x_2^{\prime}$ , are calculated as follows:

$\begin{eqnarray*} v_1^{\prime} & = & 2 (1 - u_1) - 1 \\ v_2^{\prime} & = & 2 (1 - u_2) - 1 \\ r^{\prime 2} & = & v_1^{\prime 2} + v_2^{\prime 2} \\ y^{\prime} & = & \sqrt{\frac{-2 \log(r^{\prime 2})}{r^{\prime 2}}} \\ x_1^{\prime} & = & \mu + v_1^{\prime} y^{\prime} \sqrt{\sigma^2} \\ x_2^{\prime} & = & \mu + v_2^{\prime} y^{\prime} \sqrt{\sigma^2} , \end{eqnarray*}$

which now involves the distances and are from 1.

Definition at line 971 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ NormalRandomVariable()

ns3::NormalRandomVariable::NormalRandomVariable ( )

Creates a normal distribution RNG with the default values for the mean, variance, and bound.

Definition at line 684 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ GetBound()

double ns3::NormalRandomVariable::GetBound ( ) const

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

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

Definition at line 705 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::NormalRandomVariable::GetInteger	(	uint32_t	mean,
		uint32_t	variance,
		uint32_t	bound )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	mean	Mean value for the normal distribution.
[in]	variance	Variance value for the normal distribution.
[in]	bound	Bound on values returned.

Definition at line 767 of file random-variable-stream.cc.

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

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◆ GetMean()

double ns3::NormalRandomVariable::GetMean ( ) const

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

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

Definition at line 693 of file random-variable-stream.cc.

References m_mean.

◆ GetTypeId()

TypeId ns3::NormalRandomVariable::GetTypeId ( )

static

Register this type.

Returns: The object TypeId.

Definition at line 658 of file random-variable-stream.cc.

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

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◆ GetValue() [1/2]

double ns3::NormalRandomVariable::GetValue ( )

overridevirtual

Get the next random value drawn from the distribution.

Returns: A random value.

Implements ns3::RandomVariableStream.

Definition at line 776 of file random-variable-stream.cc.

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

Referenced by GetInteger(), and GetValue().

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◆ GetValue() [2/2]

double ns3::NormalRandomVariable::GetValue	(	double	mean,
		double	variance,
		double	bound = NormalRandomVariable::INFINITE_VALUE )

Get the next random value drawn from the distribution.

Returns: A random value.

Parameters

[in]	mean	Mean value for the normal distribution.
[in]	variance	Variance value for the normal distribution.
[in]	bound	Bound on values returned.

Definition at line 711 of file random-variable-stream.cc.

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

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◆ GetVariance()

double ns3::NormalRandomVariable::GetVariance ( ) const

Returns the variance value for the normal distribution returned by this RNG stream.

Returns: The variance value for the normal distribution returned by this RNG stream.

Definition at line 699 of file random-variable-stream.cc.

References m_variance.

Member Data Documentation

◆ INFINITE_VALUE

const double ns3::NormalRandomVariable::INFINITE_VALUE = 1e307

static

Large constant to bound the range.

Definition at line 975 of file random-variable-stream.h.

Referenced by GetTypeId(), and ns3::GammaRandomVariable::GetValue().

◆ m_bound

double ns3::NormalRandomVariable::m_bound

private

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

Definition at line 1032 of file random-variable-stream.h.

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

◆ m_mean

double ns3::NormalRandomVariable::m_mean

private

The mean value for the normal distribution returned by this RNG stream.

Definition at line 1026 of file random-variable-stream.h.

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

◆ m_nextValid

bool ns3::NormalRandomVariable::m_nextValid

private

True if the next value is valid.

Definition at line 1035 of file random-variable-stream.h.

Referenced by GetValue().

◆ m_v2

double ns3::NormalRandomVariable::m_v2

private

The algorithm produces two values at a time.

Cache parameters for possible reuse.

Definition at line 1038 of file random-variable-stream.h.

Referenced by GetValue().

◆ m_variance

double ns3::NormalRandomVariable::m_variance

private

The variance value for the normal distribution returned by this RNG stream.

Definition at line 1029 of file random-variable-stream.h.

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

◆ m_y

double ns3::NormalRandomVariable::m_y

private

The algorithm produces two values at a time.

Cache parameters for possible reuse.

Definition at line 1040 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

Static Public Attributes

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ NormalRandomVariable()

Member Function Documentation

◆ GetBound()

◆ GetInteger() [1/2]

◆ GetInteger() [2/2]

◆ GetMean()

◆ GetTypeId()

◆ GetValue() [1/2]

◆ GetValue() [2/2]

◆ GetVariance()

Member Data Documentation

◆ INFINITE_VALUE

◆ m_bound

◆ m_mean

◆ m_nextValid

◆ m_v2

◆ m_variance

◆ m_y