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ns3::ErlangRandomVariable Class Reference

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

#include "random-variable-stream.h"

+ Inheritance diagram for ns3::ErlangRandomVariable:

Public Member Functions

 ErlangRandomVariable ()
 Creates an Erlang distribution RNG with the default values for k and lambda. More...
 
uint32_t GetInteger (uint32_t k, uint32_t lambda)
 Returns a random unsigned integer from an Erlang distribution with the specified k and lambda. More...
 
virtual uint32_t GetInteger (void)
 Returns a random unsigned integer from an Erlang distribution with the current k and lambda. More...
 
uint32_t GetK (void) const
 Returns the k value for the Erlang distribution returned by this RNG stream. More...
 
double GetLambda (void) const
 Returns the lambda value for the Erlang distribution returned by this RNG stream. More...
 
double GetValue (uint32_t k, double lambda)
 Returns a random double from an Erlang distribution with the specified k and lambda. More...
 
virtual double GetValue (void)
 Returns a random double from an Erlang distribution with the current k and lambda. More...
 
- Public Member Functions inherited from ns3::RandomVariableStream
 RandomVariableStream ()
 Default constructor. More...
 
virtual ~RandomVariableStream ()
 Destructor. More...
 
int64_t GetStream (void) const
 Returns the stream number for the RngStream. More...
 
bool IsAntithetic (void) const
 Check if antithetic values will be generated. More...
 
void SetAntithetic (bool isAntithetic)
 Specify whether antithetic values should be generated. More...
 
void SetStream (int64_t stream)
 Specifies the stream number for the RngStream. 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
 Get the most derived TypeId for this Object. 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 by TypeId. More...
 
void Initialize (void)
 Invoke DoInitialize on all Objects aggregated to this one. More...
 
bool IsInitialized (void) const
 Check if the object has been initialized. More...
 
- Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
 SimpleRefCount ()
 Default constructor. More...
 
 SimpleRefCount (const SimpleRefCount &o)
 Copy constructor. More...
 
uint32_t GetReferenceCount (void) const
 Get the reference count of the object. More...
 
SimpleRefCountoperator= (const SimpleRefCount &o)
 Assignment operator. 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)
 Register this type. More...
 
- 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::ObjectBase
static TypeId GetTypeId (void)
 Get the type ID. More...
 

Private Member Functions

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

Private Attributes

uint32_t m_k
 The k value for the Erlang distribution returned by this RNG stream. More...
 
double m_lambda
 The lambda value for the Erlang distribution returned by this RNG stream. More...
 

Additional Inherited Members

- Protected Member Functions inherited from ns3::RandomVariableStream
RngStreamPeek (void) const
 Get the pointer to the underlying RngStream. 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...
 

Detailed Description

The Erlang 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 Erlang distribution. It also supports the generation of single random numbers from various Erlang distributions.

The Erlang distribution is a special case of the Gamma distribution where k (= alpha) is a non-negative integer. Erlang distributed variables can be generated using a much faster algorithm than gamma variables.

The probability density function is defined over the interval [0, $+\infty$) as: $ \frac{x^{k-1} e^{-\frac{x}{\lambda}}}{\lambda^k (k-1)!}$ where $ mean = k \lambda $ and $ variance = k \lambda^2$

Here is an example of how to use this class:

uint32_t k = 5;
double lambda = 2.0;
Ptr<ErlangRandomVariable> x = CreateObject<ErlangRandomVariable> ();
x->SetAttribute ("K", IntegerValue (k));
x->SetAttribute ("Lambda", DoubleValue (lambda));
// The expected value for the mean of the values returned by a
// Erlangly distributed random variable is equal to
//
// E[value] = k * lambda .
//
double value = x->GetValue ();

Config Paths

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

Attributes

Attributes defined in parent class ns3::RandomVariableStream

No TraceSources are defined for this type.
Size of this type is 72 bytes (on a 64-bit architecture).

Definition at line 1685 of file random-variable-stream.h.

Constructor & Destructor Documentation

◆ ErlangRandomVariable()

ns3::ErlangRandomVariable::ErlangRandomVariable ( )

Creates an Erlang distribution RNG with the default values for k and lambda.

Definition at line 1098 of file random-variable-stream.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ GetExponentialValue()

double ns3::ErlangRandomVariable::GetExponentialValue ( double  mean,
double  bound 
)
private

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

Parameters
[in]meanMean value of the random variables.
[in]boundUpper 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 1167 of file random-variable-stream.cc.

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

Referenced by GetValue().

◆ GetInteger() [1/2]

uint32_t ns3::ErlangRandomVariable::GetInteger ( uint32_t  k,
uint32_t  lambda 
)

Returns a random unsigned integer from an Erlang distribution with the specified k and lambda.

Parameters
[in]kK value for the Erlang distribution.
[in]lambdaLambda value for the Erlang distribution.
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 $x$ 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, $x'$, uses (1-u), which is the distance $u$ is from the 1.

Definition at line 1147 of file random-variable-stream.cc.

References GetValue(), and NS_LOG_FUNCTION.

◆ GetInteger() [2/2]

uint32_t ns3::ErlangRandomVariable::GetInteger ( void  )
virtual

Returns a random unsigned integer from an Erlang distribution with the current k and lambda.

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 $x$ 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, $x'$, uses (1-u), which is the distance $u$ is from the 1.

Implements ns3::RandomVariableStream.

Definition at line 1160 of file random-variable-stream.cc.

References GetValue(), m_k, m_lambda, and NS_LOG_FUNCTION.

◆ GetK()

uint32_t ns3::ErlangRandomVariable::GetK ( void  ) const

Returns the k value for the Erlang distribution returned by this RNG stream.

Returns
The k value for the Erlang distribution returned by this RNG stream.

Definition at line 1105 of file random-variable-stream.cc.

References m_k, and NS_LOG_FUNCTION.

◆ GetLambda()

double ns3::ErlangRandomVariable::GetLambda ( void  ) const

Returns the lambda value for the Erlang distribution returned by this RNG stream.

Returns
The lambda value for the Erlang distribution returned by this RNG stream.

Definition at line 1111 of file random-variable-stream.cc.

References m_lambda, and NS_LOG_FUNCTION.

◆ GetTypeId()

TypeId ns3::ErlangRandomVariable::GetTypeId ( void  )
static

Register this type.

Returns
The object TypeId.

Definition at line 1081 of file random-variable-stream.cc.

References m_k, m_lambda, ns3::MakeDoubleAccessor(), ns3::MakeIntegerAccessor(), and ns3::TypeId::SetParent().

◆ GetValue() [1/2]

double ns3::ErlangRandomVariable::GetValue ( uint32_t  k,
double  lambda 
)

Returns a random double from an Erlang distribution with the specified k and lambda.

Parameters
[in]kK value for the Erlang distribution.
[in]lambdaLambda value for the Erlang distribution.
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 $x$ 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, $x'$, uses (1-u), which is the distance $u$ is from the 1.

Definition at line 1130 of file random-variable-stream.cc.

References GetExponentialValue(), and NS_LOG_FUNCTION.

◆ GetValue() [2/2]

double ns3::ErlangRandomVariable::GetValue ( void  )
virtual

Returns a random double from an Erlang distribution with the current k and lambda.

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 $x$ 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, $x'$, uses (1-u), which is 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 1154 of file random-variable-stream.cc.

References m_k, m_lambda, and NS_LOG_FUNCTION.

Referenced by GetInteger().

Member Data Documentation

◆ m_k

uint32_t ns3::ErlangRandomVariable::m_k
private

The k value for the Erlang distribution returned by this RNG stream.

Definition at line 1801 of file random-variable-stream.h.

Referenced by GetInteger(), GetK(), GetTypeId(), and GetValue().

◆ m_lambda

double ns3::ErlangRandomVariable::m_lambda
private

The lambda value for the Erlang distribution returned by this RNG stream.

Definition at line 1804 of file random-variable-stream.h.

Referenced by GetInteger(), GetLambda(), GetTypeId(), and GetValue().


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