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ns3::ErlangRandomVariable Class Reference
Random Variable Distributions

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.
 
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
int64_t GetStream (void) const
 Returns the stream number for this RNG stream. More...
 
bool IsAntithetic (void) const
 Returns true if antithetic values should be generated. More...
 
void SetAntithetic (bool isAntithetic)
 Specifies whether antithetic values should be generated. More...
 
void SetStream (int64_t stream)
 Specifies the stream number for this RNG stream. More...
 
- Public Member Functions inherited from ns3::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 Initialize (void)
 
- Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
 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
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)
 
- Static Public Member Functions inherited from ns3::RandomVariableStream
static TypeId GetTypeId (void)
 
- Static Public Member Functions inherited from ns3::Object
static TypeId GetTypeId (void)
 
- Static Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
static void Cleanup (void)
 
- Static Public Member Functions inherited from ns3::ObjectBase
static TypeId GetTypeId (void)
 

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.
 
double m_lambda
 The lambda value for the Erlang 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.
 
- Protected Member Functions inherited from ns3::Object
 Object (const Object &o)
 
virtual void DoDispose (void)
 
virtual void DoInitialize (void)
 
virtual void NotifyNewAggregate (void)
 
- Protected Member Functions inherited from ns3::ObjectBase
void ConstructSelf (const AttributeConstructionList &attributes)
 
virtual void NotifyConstructionCompleted (void)
 

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:

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

Attributes

  • K: The k value for the Erlang distribution returned by this RNG stream.
  • Lambda: The lambda value for the Erlang distribution returned by this RNG stream.
    • Set with class: ns3::DoubleValue
    • Underlying type: double -1.79769e+308:1.79769e+308
    • Initial value: 1
    • 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 are defined for this type.

Definition at line 1641 of file random-variable-stream.h.

Member Function Documentation

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
meanMean value of the random variables.
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 1126 of file random-variable-stream.cc.

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

Referenced by GetValue().

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
kK value for the Erlang distribution.
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 1106 of file random-variable-stream.cc.

References GetValue(), and NS_LOG_FUNCTION.

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 1119 of file random-variable-stream.cc.

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

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 1064 of file random-variable-stream.cc.

References m_k, and NS_LOG_FUNCTION.

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 1070 of file random-variable-stream.cc.

References m_lambda, and NS_LOG_FUNCTION.

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

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

Parameters
kK value for the Erlang distribution.
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 1089 of file random-variable-stream.cc.

References GetExponentialValue(), and NS_LOG_FUNCTION.

Referenced by RandomVariableStreamErlangTestCase::DoRun(), and RandomVariableStreamErlangAntitheticTestCase::DoRun().

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 1113 of file random-variable-stream.cc.

References m_k, m_lambda, and NS_LOG_FUNCTION.

Referenced by GetInteger().

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