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A Discrete-Event Network Simulator
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API |
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A Discrete-Event Network Simulator
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API |
The exponential distribution Random Number Generator (RNG). More...
#include "random-variable-stream.h"
Inheritance diagram for ns3::ExponentialRandomVariable: Collaboration diagram for ns3::ExponentialRandomVariable:Public Member Functions | |
| ExponentialRandomVariable () | |
| Creates an exponential distribution RNG with the default values for the mean and upper bound. More... | |
| double | GetBound () const |
| Get the configured upper bound of this RNG. More... | |
| virtual uint32_t | GetInteger () |
| Get the next random value drawn from the distribution. More... | |
| uint32_t | GetInteger (uint32_t mean, uint32_t bound) |
| Get the next random value drawn from the distribution. More... | |
| double | GetMean () const |
| Get the configured mean value of this RNG. More... | |
| double | GetValue () override |
| Get the next random value drawn from the distribution. More... | |
| double | GetValue (double mean, double bound) |
| Get the next random value drawn from the distribution. More... | |
| Public Member Functions inherited from ns3::RandomVariableStream | |
| RandomVariableStream () | |
| Default constructor. More... | |
| RandomVariableStream (const RandomVariableStream &)=delete | |
| ~RandomVariableStream () override | |
| Destructor. More... | |
| virtual uint32_t | GetInteger () |
| Get the next random value drawn from the distribution. More... | |
| int64_t | GetStream () const |
| Returns the stream number for the RngStream. More... | |
| virtual double | GetValue ()=0 |
| Get the next random value drawn from the distribution. More... | |
| bool | IsAntithetic () const |
| Check if antithetic values will be generated. More... | |
| RandomVariableStream & | operator= (const RandomVariableStream &)=delete |
| 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... | |
| ~Object () override | |
| Destructor. More... | |
| void | AggregateObject (Ptr< Object > other) |
| Aggregate two Objects together. More... | |
| void | Dispose () |
| Dispose of this Object. More... | |
| AggregateIterator | GetAggregateIterator () const |
| Get an iterator to the Objects aggregated to this one. More... | |
| TypeId | GetInstanceTypeId () const override |
| Get the most derived TypeId for this Object. More... | |
| template<typename T > | |
| Ptr< T > | GetObject () const |
| Get a pointer to the requested aggregated Object. More... | |
| template<> | |
| Ptr< Object > | GetObject () const |
| Specialization of () for objects of type ns3::Object. More... | |
| template<typename T > | |
| Ptr< T > | GetObject (TypeId tid) const |
| Get a pointer to the requested aggregated Object by TypeId. More... | |
| template<> | |
| Ptr< Object > | GetObject (TypeId tid) const |
| Specialization of (TypeId tid) for objects of type ns3::Object. More... | |
| void | Initialize () |
| Invoke DoInitialize on all Objects aggregated to this one. More... | |
| bool | IsInitialized () 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 () const |
| Get the reference count of the object. More... | |
| SimpleRefCount & | operator= (const SimpleRefCount &o) |
| Assignment operator. More... | |
| void | Ref () const |
| Increment the reference count. More... | |
| void | Unref () 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 errors. More... | |
| virtual TypeId | GetInstanceTypeId () const =0 |
| Get the most derived TypeId for this Object. 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 () |
| Register this type. More... | |
| Static Public Member Functions inherited from ns3::RandomVariableStream | |
| static TypeId | GetTypeId () |
| Register this type. More... | |
| Static Public Member Functions inherited from ns3::Object | |
| static TypeId | GetTypeId () |
| Register this type. More... | |
| Static Public Member Functions inherited from ns3::ObjectBase | |
| static TypeId | GetTypeId () |
| Get the type ID. More... | |
Private Attributes | |
| double | m_bound |
| The upper bound on values that can be returned by this RNG stream. More... | |
| double | m_mean |
| The mean value of the unbounded exponential distribution. More... | |
Additional Inherited Members | |
| Protected Member Functions inherited from ns3::RandomVariableStream | |
| RngStream * | Peek () 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 () |
| Destructor implementation. More... | |
| virtual void | DoInitialize () |
| Initialize() implementation. More... | |
| virtual void | NotifyNewAggregate () |
| 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 () |
| Notifier called once the ObjectBase is fully constructed. More... | |
| Related Functions inherited from ns3::ObjectBase | |
| static TypeId | GetObjectIid () |
| Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly. More... | |
The exponential distribution Random Number Generator (RNG).
This class supports the creation of objects that return random numbers from a fixed exponential distribution. It also supports the generation of single random numbers from various exponential distributions.
The probability density function of an exponential variable is defined as:
![\[ P(x; \alpha) dx = \alpha e^{-\alpha x} dx, \\ \quad x \in [0, +\infty) \]](../../form_16.png)
where 
and 
is the Mean configurable attribute. This distribution has variance 
.
The exponential RNG value 
is generated by
![\[ x = - \frac{\log(u)}{\alpha} = - \text{Mean} \log(u) \]](../../form_20.png)
where 
is a uniform random variable on [0,1).
Since the exponential distributions can theoretically return unbounded values, it is sometimes useful to specify a fixed upper Bound. The bounded version is defined over the interval ![$[0,b]$](../../form_21.png)
as:
![\[ P(x; \alpha, b) dx = \alpha e^{-\alpha x} dx, \\ \quad x \in [0, b] \]](../../form_22.png)
Note that in this case the true mean of the distribution is smaller than the nominal mean value:
![\[ \langle x | P(x; \alpha, b) \rangle = \frac{1}{\alpha} - \left(\frac{1}{\alpha} + b\right)\exp^{-\alpha b} \]](../../form_23.png)
Here is an example of how to use this class:
If an instance of this RNG is configured to return antithetic values, the actual value returned, 
, is generated as follows:
![\[ x' = - \frac{\log(1 - u)}{\alpha} = - Mean \log(1 - u), \]](../../form_25.png)
where is a uniform random variable on [0,1).
ns3::ExponentialRandomVariable is accessible through the following paths with Config::Set and Config::Connect:
No TraceSources are defined for this type.
Size of this type is 72 bytes (on a 64-bit architecture).
Definition at line 551 of file random-variable-stream.h.
| ns3::ExponentialRandomVariable::ExponentialRandomVariable | ( | ) |
Creates an exponential distribution RNG with the default values for the mean and upper bound.
Definition at line 400 of file random-variable-stream.cc.
References NS_LOG_FUNCTION.
| double ns3::ExponentialRandomVariable::GetBound | ( | ) | const |
Get the configured upper bound of this RNG.
Definition at line 414 of file random-variable-stream.cc.
References m_bound, and NS_LOG_FUNCTION.
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virtual |
Get the next random value drawn from the distribution.
Reimplemented from ns3::RandomVariableStream.
Definition at line 153 of file random-variable-stream.cc.
Get the next random value drawn from the distribution.
| [in] | mean | Mean value of the unbounded exponential distribution. |
| [in] | bound | Upper bound on values returned. |
Definition at line 445 of file random-variable-stream.cc.
References GetValue(), and NS_LOG_FUNCTION.
Here is the call graph for this function:| double ns3::ExponentialRandomVariable::GetMean | ( | ) | const |
Get the configured mean value of this RNG.
Definition at line 407 of file random-variable-stream.cc.
References m_mean, and NS_LOG_FUNCTION.
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static |
Register this type.
Definition at line 380 of file random-variable-stream.cc.
References m_bound, m_mean, ns3::MakeDoubleAccessor(), and ns3::TypeId::SetParent().
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Get the next random value drawn from the distribution.
Implements ns3::RandomVariableStream.
Definition at line 452 of file random-variable-stream.cc.
References GetValue(), m_bound, m_mean, and NS_LOG_FUNCTION.
Referenced by GetInteger(), and GetValue().
Here is the call graph for this function: Here is the caller graph for this function:Get the next random value drawn from the distribution.
| [in] | mean | Mean value of the unbounded exponential distribution. |
| [in] | bound | Upper bound on values returned. |
Definition at line 421 of file random-variable-stream.cc.
References ns3::RandomVariableStream::IsAntithetic(), NS_LOG_FUNCTION, ns3::RandomVariableStream::Peek(), and ns3::RngStream::RandU01().
Referenced by ns3::UanMacRc::Associate(), ns3::UanMacRc::AssociateTimeout(), RngExponentialTestCase::ChiSquaredTest(), Emitter::Count(), Emitter::DoInitialize(), Emitter::Emit(), ns3::ThreeGppHttpVariables::GetParsingTime(), ns3::ThreeGppHttpVariables::GetReadingTime(), SampleEmitter::Report(), SampleEmitter::Reschedule(), ns3::UanMacRc::RtsTimeout(), ns3::UanMacRc::ScheduleData(), Experiment::SendMultiDestinations(), and ns3::UanMacRc::SendRts().
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private |
The upper bound on values that can be returned by this RNG stream.
Definition at line 600 of file random-variable-stream.h.
Referenced by GetBound(), GetTypeId(), and GetValue().
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private |
The mean value of the unbounded exponential distribution.
Definition at line 597 of file random-variable-stream.h.
Referenced by GetMean(), GetTypeId(), and GetValue().
1.9.3 
