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ns3::ParetoRandomVariable Class Reference
Core » Random Variables

The Pareto distribution Random Number Generator (RNG). More...

#include "random-variable-stream.h"

Inheritance diagram for ns3::ParetoRandomVariable:
Collaboration diagram for ns3::ParetoRandomVariable:

Public Member Functions

 ParetoRandomVariable ()
 Creates a Pareto distribution RNG with the default values for the mean, the 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 GetScale () const
 Returns the scale parameter for the Pareto distribution returned by this RNG stream.
double GetShape () const
 Returns the shape parameter for the Pareto 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 final
 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.
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_bound
 The upper bound on values that can be returned by this RNG stream.
double m_scale
 The scale parameter for the Pareto distribution returned by this RNG stream.
double m_shape
 The shape parameter for the Pareto 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
 Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly.

Detailed Description

The Pareto distribution Random Number Generator (RNG).

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

The probability density function of a Pareto variable is:

\[ P(x; x_m, \alpha) dx = \alpha \frac{x_m^\alpha}{x^{\alpha + 1}} dx, \\ \quad x \in [x_m, +\infty) \]

where the minimum value $x_m > 0$ is called the Scale parameter and $ \alpha > 0$ is called the Pareto index or Shape parameter.

The resulting distribution will have mean

\[ \mu = x_m \frac{\alpha}{\alpha - 1} \mbox{ for $\alpha > 1$} \]

and variance

\[ \sigma^2 = x_m \frac{1}{(\alpha - 1)(\alpha - 2)} \mbox { for $\alpha > 2$} \]

The minimum value $x_m$ can be inferred from the desired mean $\mu$ and the parameter $\alpha$ with the equation

\[ x_m = \mu \frac{\alpha - 1}{\alpha} \mbox{ for $\alpha > 1$} \]

The Pareto RNG value $x$ is generated by

\[ x = \frac{x_m}{u^{\frac{1}{\alpha}}} \]

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

Bounded Distribution

Since Pareto distributions can theoretically return unbounded values, it is sometimes useful to specify a fixed upper Bound. The bounded version is defined over the interval $ x \in [x_m, 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 = 2.0;
Ptr<ParetoRandomVariable> x = CreateObject<ParetoRandomVariable> ();
x->SetAttribute ("Scale", DoubleValue (scale));
x->SetAttribute ("Shape", DoubleValue (shape));
double value = x->GetValue ();
ns3::DoubleValue
This class can be used to hold variables of floating point type such as 'double' or 'float'.
Definition double.h:31
ns3::Ptr
Smart pointer class similar to boost::intrusive_ptr.
Definition ptr.h:66
ns3::CreateObject
Ptr< T > CreateObject(Args &&... args)
Create an object by type, with varying number of constructor parameters.
Definition object.h:619
Antithetic Values.

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

\[ x' = \frac{x_m}{{(1 - u)}^{\frac{1}{\alpha}}} , \]

which now involves the distance $u$ is from 1 in the denominator.

Definition at line 679 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ ParetoRandomVariable()

ns3::ParetoRandomVariable::ParetoRandomVariable ( )

Creates a Pareto distribution RNG with the default values for the mean, the shape, and upper bound.

Definition at line 477 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Referenced by GetTypeId().

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Member Function Documentation

◆ GetBound()

double ns3::ParetoRandomVariable::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 497 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::ParetoRandomVariable::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]scaleMean parameter for the Pareto distribution.
[in]shapeShape parameter for the Pareto distribution.
[in]boundUpper bound on values returned.

Definition at line 528 of file random-variable-stream.cc.

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

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◆ GetScale()

double ns3::ParetoRandomVariable::GetScale ( ) const

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

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

Definition at line 485 of file random-variable-stream.cc.

References m_scale.

◆ GetShape()

double ns3::ParetoRandomVariable::GetShape ( ) const

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

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

Definition at line 491 of file random-variable-stream.cc.

References m_shape.

◆ GetTypeId()

TypeId ns3::ParetoRandomVariable::GetTypeId ( )
static

Register this type.

Returns
The object TypeId.

Definition at line 449 of file random-variable-stream.cc.

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

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◆ GetValue() [1/2]

double ns3::ParetoRandomVariable::GetValue ( )
overridevirtual

Get the next random value drawn from the distribution.

Returns
A random value.

Implements ns3::RandomVariableStream.

Definition at line 537 of file random-variable-stream.cc.

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

Referenced by GetInteger(), and GetValue().

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◆ GetValue() [2/2]

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

Get the next random value drawn from the distribution.

Returns
A random value.
Parameters
[in]scaleMean parameter for the Pareto distribution.
[in]shapeShape parameter for the Pareto distribution.
[in]boundUpper bound on values returned.

Definition at line 503 of file random-variable-stream.cc.

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

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Member Data Documentation

◆ m_bound

double ns3::ParetoRandomVariable::m_bound
private

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

Definition at line 735 of file random-variable-stream.h.

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

◆ m_scale

double ns3::ParetoRandomVariable::m_scale
private

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

Definition at line 729 of file random-variable-stream.h.

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

◆ m_shape

double ns3::ParetoRandomVariable::m_shape
private

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

Definition at line 732 of file random-variable-stream.h.

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

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