A Discrete-Event Network Simulator
API
ns3::Scheduler Class Referenceabstract

Maintain the event list. More...

#include "scheduler.h"

+ Inheritance diagram for ns3::Scheduler:
+ Collaboration diagram for ns3::Scheduler:

Classes

struct  Event
 Scheduler event. More...
 
struct  EventKey
 Structure for sorting and comparing Events. More...
 

Public Member Functions

 ~Scheduler () override=0
 Destructor. More...
 
virtual void Insert (const Event &ev)=0
 Insert a new Event in the schedule. More...
 
virtual bool IsEmpty () const =0
 Test if the schedule is empty. More...
 
virtual Event PeekNext () const =0
 Get a pointer to the next event. More...
 
virtual void Remove (const Event &ev)=0
 Remove a specific event from the event list. More...
 
virtual Event RemoveNext ()=0
 Remove the earliest event from the event list. 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< ObjectGetObject () 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< ObjectGetObject (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[[maybe_unused]])
 Copy constructor. More...
 
uint32_t GetReferenceCount () const
 Get the reference count of the object. More...
 
SimpleRefCountoperator= (const SimpleRefCount &o[[maybe_unused]])
 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...
 
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::Object
static TypeId GetTypeId ()
 Register this type. More...
 
- Static Public Member Functions inherited from ns3::ObjectBase
static TypeId GetTypeId ()
 Get the type ID. More...
 

Additional Inherited Members

- 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...
 

Detailed Description

Maintain the event list.

In ns-3 the Scheduler manages the future event list. There are several different Scheduler implementations with different time and space tradeoffs. Which one is "best" depends in part on the characteristics of the model being executed. For optimized production work common practice is to benchmark each Scheduler on the model of interest. The utility program utils/bench-scheduler.cc can do simple benchmarking of each SchedulerImpl against an exponential or user-provided event time distribution.

The most important Scheduler functions for time performance are (usually) Scheduler::Insert (for new events) and Scheduler::RemoveNext (for pulling off the next event to execute). Simulator::Cancel is usually implemented by simply setting a bit on the Event, but leaving it in the Scheduler; the Simulator just skips those events as they are encountered.

For models which need a large event list the Scheduler overhead and per-event memory cost could also be important. Some models rely heavily on Scheduler::Cancel, however, and these might benefit from using Scheduler::Remove instead, to reduce the size of the event list, at the time cost of actually removing events from the list.

A summary of the main characteristics of each SchedulerImpl is provided below. See the individual Scheduler pages for details on the complexity of the other API calls. (Memory overheads assume pointers and std::size_t are both 8 bytes.)

Scheduler Type Complexity
SchedulerImpl Method Time Space
Insert() RemoveNext() Overhead Per Event
CalendarScheduler <std::list> [] Constant Constant 24 bytes 16 bytes
HeapScheduler Heap on std::vector Logarithmic Logarithmic 24 bytes 0
ListScheduler std::list Linear Constant 24 bytes 16 bytes
MapScheduler std::map Logarithmic Constant 40 bytes 32 bytes
PriorityQueueScheduler std::priority_queue<,std::vector> Logarithmic Logarithmic 24 bytes 0

It is possible to change the Scheduler choice during a simulation, via Simulator::SetScheduler.

The Scheduler base class specifies the interface used to maintain the event list. If you want to provide a new event list scheduler, you need to create a subclass of this base class and implement all the pure virtual methods defined here.

The only tricky aspect of this API is the memory management of the EventImpl pointer which is a member of the Event data structure. The lifetime of this pointer is assumed to always be longer than the lifetime of the Scheduler class which means that the caller is responsible for ensuring that this invariant holds through calling EventId::Ref and SimpleRefCount::Unref at the right time. Typically, EventId::Ref is called before Insert and SimpleRefCount::Unref is called after a call to one of the Remove methods.

Definition at line 156 of file scheduler.h.

Constructor & Destructor Documentation

◆ ~Scheduler()

ns3::Scheduler::~Scheduler ( )
overridepure virtual

Destructor.

Definition at line 38 of file scheduler.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ GetTypeId()

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

Register this type.

Returns
The object TypeId.

Definition at line 44 of file scheduler.cc.

References ns3::TypeId::SetParent().

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◆ Insert()

virtual void ns3::Scheduler::Insert ( const Event ev)
pure virtual

Insert a new Event in the schedule.

Parameters
[in]evEvent to store in the event list

Implemented in ns3::PriorityQueueScheduler, ns3::MapScheduler, ns3::ListScheduler, ns3::HeapScheduler, and ns3::CalendarScheduler.

◆ IsEmpty()

virtual bool ns3::Scheduler::IsEmpty ( ) const
pure virtual

Test if the schedule is empty.

Returns
true if the event list is empty and false otherwise.

Implemented in ns3::PriorityQueueScheduler, ns3::MapScheduler, ns3::ListScheduler, ns3::HeapScheduler, and ns3::CalendarScheduler.

◆ PeekNext()

virtual Event ns3::Scheduler::PeekNext ( ) const
pure virtual

Get a pointer to the next event.

This method cannot be invoked if the list is empty.

Returns
A pointer to the next earliest event. The caller takes ownership of the returned pointer.

Implemented in ns3::PriorityQueueScheduler, ns3::MapScheduler, ns3::ListScheduler, ns3::HeapScheduler, and ns3::CalendarScheduler.

◆ Remove()

virtual void ns3::Scheduler::Remove ( const Event ev)
pure virtual

Remove a specific event from the event list.

This method cannot be invoked if the list is empty.

Parameters
[in]evThe event to remove

Implemented in ns3::PriorityQueueScheduler, ns3::MapScheduler, ns3::ListScheduler, ns3::HeapScheduler, and ns3::CalendarScheduler.

◆ RemoveNext()

virtual Event ns3::Scheduler::RemoveNext ( )
pure virtual

Remove the earliest event from the event list.

This method cannot be invoked if the list is empty.

Returns
The Event.

Implemented in ns3::PriorityQueueScheduler, ns3::MapScheduler, ns3::ListScheduler, ns3::HeapScheduler, and ns3::CalendarScheduler.


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