ThreadPool Class Reference

#include <CUThreadPool.h>

Inheritance diagram for ThreadPool:

Public Member Functions
void	addTask (const std::function< void()> &task)
void	stop ()
bool	isStopped () const
bool	isShutdown () const
	~ThreadPool ()
virtual bool	init (int threads=4)

Static Public Member Functions
static ThreadPool *	create (int threads=4)

Public Attributes
CC_CONSTRUCTOR_ACCESS	__pad0__: ThreadPool()

Protected Member Functions
void	threadFunc ()

Protected Attributes
std::vector< std::thread >	_workers
std::queue< std::function< void()> >	_taskQueue
std::mutex	_queueMutex
std::condition_variable	_taskCondition
bool	_detach
bool	_stop
int	_complete

Detailed Description

Class to providing a collection of worker threads.

This is a general purpose class for performing tasks asynchronously. There is no notification process for when a task is complete. Instead, your task should either set a flag, or execute a callback when it is done.

This code is largely taken from the Cocos2d file AudioEngine.cpp, from the code for asynchronous asset loading. We have made some safety changes. In particular, stopping a thread pool does not shut it down immediately; it just marks it for shutdown. Because of mutex locks, it is not safe to delete a thread pool until it is completely shutdown.

More importantly, we no longer allow for detached threads. This makes no sense in this application, because the threads share a resource (_taskQueue) with the main thread that will be deleted. It is therefore unsafe for the threads to ever detach. I have no idea who thought this was a good idea in AudioEngine.cpp.

See the class CUAssetManager for an example of how to use a thread pool.

Constructor & Destructor Documentation

ThreadPool::~ThreadPool

(

)

Deletes this thread pool, destroying all resources.

It is a bad idea to destroy the thread pool if the pool is not yet shut down. The task queue is shared by the child threads, so we cannot delete it until all the threads complete. This destructor will block unti showndown.

Member Function Documentation

void ThreadPool::addTask

(

const std::function< void()> &

task

)

Adds a task to the thread pool.

A task is a void returning function with no parameters. If you need state in the task, you should use a method call for the state. The task will not be executed immediately, but must wait for the first available worker.

Parameters

task	the task function to add to the thread pool

NS_CC_BEGIN ThreadPool * ThreadPool::create ( int  threads = 4 )

static

Creates a thread pool with the given number of threads.

You can specify the number of simultaneous worker threads. 4 is generally a good number, even if you have a lot of tasks. Much more than the number of cores on a machine is counter-productive.

Parameters

threads

the number of threads in this pool

Returns

An autoreleased thread pool

bool ThreadPool::init ( int  threads = 4 )

virtual

Initializes a thread pool with the given number of threads.

You can specify the number of simultaneous worker threads. 4 is generally a good number, even if you have a lot of tasks. Much more than the number of cores on a machine is counter-productive.

Parameters

threads

the number of threads in this pool

Returns

true if the obstacle is initialized properly, false otherwise.

bool ThreadPool::isShutdown ( ) const

inline

Returns whether the thread pool has been shut down.

A shut down thread pool has no active threads and is safe for deletion.

Returns

whether the thread pool has been shut down.

bool ThreadPool::isStopped ( ) const

inline

Returns whether the thread pool has been stopped.

A stopped thread pool is marked for shutdown, but it shutdown has not necessarily completed. Shutdown will be complete when the current child threads have finished with their tasks.

Returns

whether the thread pool has been stopped.

void ThreadPool::stop

(

)

Stop the thread pool, marking it for shut down.

A stopped thread pool is marked for shutdown, but it shutdown has not necessarily completed. Shutdown will be complete when the current child threads have finished with their tasks.

void ThreadPool::threadFunc ( )

protected

The body function of a single thread; it pulls tasks from the task queue

Member Data Documentation

int ThreadPool::_complete

protected

The number of child threads that are completed

bool ThreadPool::_detach

protected

Whether or not to detach the threads

std::mutex ThreadPool::_queueMutex

protected

A mutex lock for the task queue

bool ThreadPool::_stop

protected

Whether or not the thread pool has been marked for shutdown

std::condition_variable ThreadPool::_taskCondition

protected

A condition variable to manage tasks waiting for a worker

std::queue< std::function<void()> > ThreadPool::_taskQueue

protected

Tasks waiting to be assigned to a thread

std::vector<std::thread> ThreadPool::_workers

protected

The individual worker threads for this thread pool

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

• /Users/wmwhite/Developer/cocos2d-cornell/cocos/cornell/CUThreadPool.h
• /Users/wmwhite/Developer/cocos2d-cornell/cocos/cornell/CUThreadPool.cpp