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

#include <random-variable-stream.h>

Inheritance diagram for ns3::ZipfRandomVariable:

Collaboration diagram for ns3::ZipfRandomVariable:

Public Member Functions
	ZipfRandomVariable ()
	Creates a Zipf distribution RNG with the default values for n and alpha.
double	GetAlpha (void) const
	Returns the alpha value for the Zipf distribution returned by this RNG stream.
uint32_t	GetInteger (uint32_t n, uint32_t alpha)
	Returns a random unsigned integer from a Zipf distribution with the specified n and alpha.
virtual uint32_t	GetInteger (void)
	Returns a random unsigned integer from a Zipf distribution with the current n and alpha.
uint32_t	GetN (void) const
	Returns the n value for the Zipf distribution returned by this RNG stream.
double	GetValue (uint32_t n, double alpha)
	Returns a random double from a Zipf distribution with the specified n and alpha.
virtual double	GetValue (void)
	Returns a random double from a Zipf distribution with the current n and alpha.
Public Member Functions inherited from ns3::RandomVariableStream
	RandomVariableStream ()
virtual	~RandomVariableStream ()
int64_t	GetStream (void) const
	Returns the stream number for this RNG stream.
bool	IsAntithetic (void) const
	Returns true if antithetic values should be generated.
void	SetAntithetic (bool isAntithetic)
	Specifies whether antithetic values should be generated.
void	SetStream (int64_t stream)
	Specifies the stream number for this RNG stream.
Public Member Functions inherited from ns3::Object
	Object ()
virtual	~Object ()
void	AggregateObject (Ptr< Object > other)
void	Dispose (void)
AggregateIterator	GetAggregateIterator (void) const
virtual TypeId	GetInstanceTypeId (void) const
template<typename T >
Ptr< T >	GetObject (void) const
template<typename T >
Ptr< T >	GetObject (TypeId tid) const
void	Start (void)
Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount ()
	SimpleRefCount (const SimpleRefCount &o)
uint32_t	GetReferenceCount (void) const
SimpleRefCount &	operator= (const SimpleRefCount &o)
void	Ref (void) const
void	Unref (void) const
Public Member Functions inherited from ns3::ObjectBase
virtual	~ObjectBase ()
void	GetAttribute (std::string name, AttributeValue &value) const
bool	GetAttributeFailSafe (std::string name, AttributeValue &attribute) const
void	SetAttribute (std::string name, const AttributeValue &value)
bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)
bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)
bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)
bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)
bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)

Static Public Member Functions
static TypeId	GetTypeId (void)
	This method returns the TypeId associated to ns3::ZipfRandomVariable.

Private Attributes
double	m_alpha
	The alpha value for the Zipf distribution returned by this RNG stream.
double	m_c
	The normalization constant.
uint32_t	m_n
	The n value for the Zipf distribution returned by this RNG stream.

Additional Inherited Members
Protected Member Functions inherited from ns3::RandomVariableStream
RngStream *	Peek (void) const
	Returns a pointer to the underlying RNG stream.

Detailed Description

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

The Zipf's law states that given some corpus of natural language utterances, the frequency of any word is inversely proportional to its rank in the frequency table.

Zipf's distribution has two parameters, alpha and N, where: $\alpha > 0$ (real) and $N \in \{1,2,3 \dots\}$ (integer). Probability Mass Function is $f(k; \alpha, N) = k^{-\alpha}/ H_{N,\alpha}$ where $H_{N,\alpha} = \sum_{m=1}^N m^{-\alpha}$

Here is an example of how to use this class:

uint32_t n = 1;
double alpha = 2.0;
Ptr<ZipfRandomVariable> x = CreateObject<ZipfRandomVariable> ();
x->SetAttribute ("N", IntegerValue (n));
x->SetAttribute ("Alpha", DoubleValue (alpha));
// The expected value for the mean of the values returned by a
// Zipfly distributed random variable is equal to 
//
//                   H
//                    N, alpha - 1
//     E[value]  =  ---------------
//                     H
//                      N, alpha
//                          
// where
//
//                    N   
//                   ---    
//                   \     -alpha
//     H          =  /    m        .
//      N, alpha     ---
//                   m=1    
//                 
// For this test,
//
//                      -(alpha - 1)
//                     1
//     E[value]  =  ---------------
//                      -alpha
//                     1
//
//               =  1  .
//               
double value = x->GetValue ();

Definition at line 2049 of file random-variable-stream.h.

Constructor & Destructor Documentation

ns3::ZipfRandomVariable::ZipfRandomVariable ( )

Creates a Zipf distribution RNG with the default values for n and alpha.

Definition at line 1174 of file random-variable-stream.cc.

Member Function Documentation

double ns3::ZipfRandomVariable::GetAlpha ( void ) const

Returns the alpha value for the Zipf distribution returned by this RNG stream.

Returns: The alpha value for the Zipf distribution returned by this RNG stream.

Definition at line 1185 of file random-variable-stream.cc.

References m_alpha.

uint32_t ns3::ZipfRandomVariable::GetInteger	(	uint32_t	n,
		uint32_t	alpha
	)

Returns a random unsigned integer from a Zipf distribution with the specified n and alpha.

Parameters

n	N value for the Zipf distribution.
alpha	Alpha value for the Zipf 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 1222 of file random-variable-stream.cc.

References GetValue().

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uint32_t ns3::ZipfRandomVariable::GetInteger ( void )

virtual

Returns a random unsigned integer from a Zipf distribution with the current n and alpha.

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 1233 of file random-variable-stream.cc.

References GetValue(), m_alpha, and m_n.

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uint32_t ns3::ZipfRandomVariable::GetN ( void ) const

Returns the n value for the Zipf distribution returned by this RNG stream.

Returns: The n value for the Zipf distribution returned by this RNG stream.

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

References m_n.

TypeId ns3::ZipfRandomVariable::GetTypeId ( void )

static

This method returns the TypeId associated to ns3::ZipfRandomVariable.

This object is accessible through the following paths with Config::Set and Config::Connect:

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/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanPitch/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::GaussMarkovMobilityModel/MeanVelocity/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Pause/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomDirection2dMobilityModel/Speed/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Direction/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWalk2dMobilityModel/Speed/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Pause/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/X/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/Y/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomBoxPositionAllocator/Z/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomDiscPositionAllocator/Rho/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomDiscPositionAllocator/Theta/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomRectanglePositionAllocator/X/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/PositionAllocator/$ns3::RandomRectanglePositionAllocator/Y/$ns3::ZipfRandomVariable
/NodeList/[i]/$ns3::MobilityModel/$ns3::RandomWaypointMobilityModel/Speed/$ns3::ZipfRandomVariable
/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OffTime/$ns3::ZipfRandomVariable
/NodeList/[i]/ApplicationList/[i]/$ns3::OnOffApplication/OnTime/$ns3::ZipfRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::CsmaNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ZipfRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::PointToPointNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ZipfRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::SimpleNetDevice/ReceiveErrorModel/$ns3::RateErrorModel/RanVar/$ns3::ZipfRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationDelayModel/$ns3::RandomPropagationDelayModel/Variable/$ns3::ZipfRandomVariable
/NodeList/[i]/DeviceList/[i]/$ns3::WifiNetDevice/Channel/$ns3::YansWifiChannel/PropagationLossModel/$ns3::RandomPropagationLossModel/Variable/$ns3::ZipfRandomVariable

Attributes defined for this type:

N: The n value for the Zipf distribution returned by this RNG stream.
- Set with class: ns3::IntegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 1
- Flags: construct write read
Alpha: The alpha value for the Zipf distribution returned by this RNG stream.
- Set with class: ns3::DoubleValue
- Underlying type: double -1.79769e+308:1.79769e+308
- Initial value: 0
- Flags: construct write read

Attributes defined in parent class ns3::RandomVariableStream:

Stream: The stream number for this RNG stream. -1 means "allocate a stream automatically". Note that if -1 is set, Get will return -1 so that it is not possible to know which value was automatically allocated.
- Set with class: ns3::IntegerValue
- Underlying type: int64_t -9223372036854775808:9223372036854775807
- Initial value: -1
- Flags: construct write read
Antithetic: Set this RNG stream to generate antithetic values
- Set with class: BooleanValue
- Underlying type: bool
- Initial value: false
- Flags: construct write read

No TraceSources defined for this type.

Reimplemented from ns3::RandomVariableStream.

Definition at line 1158 of file random-variable-stream.cc.

References m_alpha, m_n, and ns3::TypeId::SetParent().

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double ns3::ZipfRandomVariable::GetValue	(	uint32_t	n,
		double	alpha
	)

Returns a random double from a Zipf distribution with the specified n and alpha.

Parameters

n	N value for the Zipf distribution.
alpha	Alpha value for the Zipf 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 1191 of file random-variable-stream.cc.

References ns3::RandomVariableStream::IsAntithetic(), m_alpha, m_c, m_n, ns3::RandomVariableStream::Peek(), and ns3::RngStream::RandU01().

Referenced by RandomVariableStreamZipfTestCase::DoRun(), and RandomVariableStreamZipfAntitheticTestCase::DoRun().

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double ns3::ZipfRandomVariable::GetValue ( void )

virtual

Returns a random double from a Zipf distribution with the current n and alpha.

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 1228 of file random-variable-stream.cc.

References m_alpha, and m_n.

Referenced by GetInteger().

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