edm::SerialTaskQueue Class Reference

#include <SerialTaskQueue.h>

Classes
class	QueuedTask
class	TaskBase

Public Member Functions
bool	isPaused () const
	Checks to see if the queue has been paused. More...
bool	pause ()
	Pauses processing of additional tasks from the queue. More...
template<typename T >
void	push (const T &iAction)
	asynchronously pushes functor iAction into queue More...
template<typename T >
tbb::task *	pushAndGetNextTaskToRun (const T &iAction)
	asynchronously pushes functor iAction into queue and finds next task to execute More...
template<typename T >
void	pushAndWait (const T &iAction)
	synchronously pushes functor iAction into queue More...
bool	resume ()
	Resumes processing if the queue was paused. More...
	SerialTaskQueue ()
	~SerialTaskQueue ()

Private Member Functions
tbb::task *	finishedTask ()
const SerialTaskQueue &	operator= (const SerialTaskQueue &)=delete
TaskBase *	pickNextTask ()
tbb::task *	pushAndGetNextTask (TaskBase *)
void	pushAndWait (tbb::empty_task *iWait, TaskBase *)
void	pushTask (TaskBase *)
	SerialTaskQueue (const SerialTaskQueue &)=delete

Private Attributes
std::atomic< unsigned long >	m_pauseCount
std::atomic< bool >	m_taskChosen
tbb::concurrent_queue< TaskBase * >	m_tasks

Friends
class	TaskBase

Detailed Description

Definition at line 65 of file SerialTaskQueue.h.

Constructor & Destructor Documentation

edm::SerialTaskQueue::SerialTaskQueue ( )

inline

Definition at line 68 of file SerialTaskQueue.h.

References ~SerialTaskQueue().

Referenced by pause().

                       :
      m_taskChosen(false),
      m_pauseCount{0}
      {  }

SerialTaskQueue::~SerialTaskQueue

(

)

Definition at line 26 of file SerialTaskQueue.cc.

References isPaused(), m_taskChosen, m_tasks, or, and pushAndWait().

Referenced by SerialTaskQueue().

{
  //be certain all tasks have completed
  bool isEmpty = m_tasks.empty();
  bool isTaskChosen = m_taskChosen;
  if ( (not isEmpty and not isPaused()) or isTaskChosen) {
    pushAndWait([]() {return;});
  }
}

edm::SerialTaskQueue::SerialTaskQueue ( const SerialTaskQueue &  )

privatedelete

Member Function Documentation

tbb::task * SerialTaskQueue::finishedTask ( )

private

Definition at line 68 of file SerialTaskQueue.cc.

References m_taskChosen, and pickNextTask().

Referenced by edm::SerialTaskQueue::TaskBase::finishedTask().

                              {
  m_taskChosen.store(false);
  return pickNextTask();
}

bool edm::SerialTaskQueue::isPaused ( ) const

inline

Checks to see if the queue has been paused.

Returns

true if the queue is paused

See also

pause(), resume()

Definition at line 80 of file SerialTaskQueue.h.

References m_pauseCount.

Referenced by ~SerialTaskQueue().

{ return m_pauseCount.load()==0;}

const SerialTaskQueue& edm::SerialTaskQueue::operator= ( const SerialTaskQueue &  )

privatedelete

Referenced by pause().

bool edm::SerialTaskQueue::pause ( )

inline

Pauses processing of additional tasks from the queue.

Any task already running will not be paused however once that running task finishes no further tasks will be started. Multiple calls to pause() are allowed, however each call to pause() must be balanced by a call to resume().

Returns

false if queue was already paused.

See also

resume(), isPaused()

Definition at line 92 of file SerialTaskQueue.h.

References m_pauseCount, operator=(), push(), pushAndGetNextTaskToRun(), pushAndWait(), resume(), and SerialTaskQueue().

                   {
         return 1 == ++m_pauseCount;
      }

SerialTaskQueue::TaskBase * SerialTaskQueue::pickNextTask ( )

private

Definition at line 74 of file SerialTaskQueue.cc.

References likely, m_pauseCount, m_taskChosen, m_tasks, and lumiQTWidget::t.

Referenced by finishedTask(), pushAndGetNextTask(), and resume().

                              {
  
  bool expect = false;
  if likely(0 == m_pauseCount and m_taskChosen.compare_exchange_strong(expect,true)) {
    TaskBase* t=nullptr;
    if likely(m_tasks.try_pop(t)) {
      return t;
    }
    //no task was actually pulled
    m_taskChosen.store(false);
    
    //was a new entry added after we called 'try_pop' but before we did the clear?
    expect = false;
    if(not m_tasks.empty() and m_taskChosen.compare_exchange_strong(expect,true)) {
      TaskBase* t=nullptr;
      if(m_tasks.try_pop(t)) {
        return t;
      }
      //no task was still pulled since a different thread beat us to it
      m_taskChosen.store(false);
      
    }
  }
  return nullptr;
}

template<typename T >

void SerialTaskQueue::push

(

const T &

iAction

)

asynchronously pushes functor iAction into queue

The function will return immediately and iAction will either process concurrently with the calling thread or wait until the protected resource becomes available or until a CPU becomes available.

Parameters

[in]

iAction

Must be a functor that takes no arguments and return no values.

Definition at line 186 of file SerialTaskQueue.h.

References pushTask().

Referenced by pause().

                                              {
      QueuedTask<T>* pTask{ new (tbb::task::allocate_root()) QueuedTask<T>{iAction} };
      pTask->setQueue(this);
      pushTask(pTask);
   }

tbb::task * SerialTaskQueue::pushAndGetNextTask ( TaskBase *  iTask )

private

Definition at line 57 of file SerialTaskQueue.cc.

References likely, m_tasks, and pickNextTask().

Referenced by pushAndGetNextTaskToRun(), pushAndWait(), and pushTask().

                                                   {
  tbb::task* returnValue{nullptr};
  if likely(nullptr!=iTask) {
    m_tasks.push(iTask);
    returnValue = pickNextTask();
  }
  return returnValue;
}

template<typename T >

tbb::task * SerialTaskQueue::pushAndGetNextTaskToRun

(

const T &

iAction

)

asynchronously pushes functor iAction into queue and finds next task to execute

This function is useful if you are accessing the SerialTaskQueue for the execute() method of a TBB task and want to efficiently schedule the next task from the queue. In that case you can take the return value and return it directly from your execute() method. The function will return immediately and not wait for iAction to run.

Parameters

[in]

iAction

Must be a functor that takes no arguments and return no values.

Returns

Returns either the next task that the user must schedule with TBB or a nullptr.

Definition at line 202 of file SerialTaskQueue.h.

References pushAndGetNextTask().

Referenced by pause().

                                                                     {
      QueuedTask<T>* pTask{ new (tbb::task::allocate_root()) QueuedTask<T>{iAction} };
      pTask->setQueue(this);
      return pushAndGetNextTask(pTask);
   }

template<typename T >

void SerialTaskQueue::pushAndWait

(

const T &

iAction

)

synchronously pushes functor iAction into queue

The function will wait until iAction has completed before returning. If another task is already running on the queue, the system is allowed to find another TBB task to execute while waiting for the iAction to finish. In that way the core is not idled while waiting.

Parameters

[in]

iAction

Must be a functor that takes no arguments and return no values.

Definition at line 193 of file SerialTaskQueue.h.

Referenced by pause(), and ~SerialTaskQueue().

                                                     {
      tbb::empty_task* waitTask = new (tbb::task::allocate_root()) tbb::empty_task;
      waitTask->set_ref_count(2);
      QueuedTask<T>* pTask{ new (waitTask->allocate_child()) QueuedTask<T>{iAction} };
      pTask->setQueue(this);
      pushAndWait(waitTask,pTask);
   }

void SerialTaskQueue::pushAndWait ( tbb::empty_task *  iWait, TaskBase *  iTask  )

private

Definition at line 100 of file SerialTaskQueue.cc.

References pyrootRender::destroy(), likely, and pushAndGetNextTask().

                                                                       {
   auto nextTask = pushAndGetNextTask(iTask);
   if likely(nullptr != nextTask) {
     if likely(nextTask == iTask) {
        //spawn and wait for all requires the task to have its parent set
        iWait->spawn_and_wait_for_all(*nextTask);
     } else {
        tbb::task::spawn(*nextTask);
        iWait->wait_for_all();
     }
   } else {
     //a task must already be running in this queue
     iWait->wait_for_all();              
   }
   tbb::task::destroy(*iWait);
}

void SerialTaskQueue::pushTask ( TaskBase *  iTask )

private

Definition at line 49 of file SerialTaskQueue.cc.

References pushAndGetNextTask(), and lumiQTWidget::t.

Referenced by push().

                                         {
  tbb::task* t = pushAndGetNextTask(iTask);
  if(nullptr!=t) {
    tbb::task::spawn(*t);      
  }
}

bool SerialTaskQueue::resume

(

)

Resumes processing if the queue was paused.

Multiple calls to resume() are allowed if there were multiple calls to pause(). Only when we reach as many resume() calls as pause() calls will the queue restart.

Returns

true if the call really restarts the queue

See also

pause(), isPaused()

Definition at line 37 of file SerialTaskQueue.cc.

References m_pauseCount, pickNextTask(), and lumiQTWidget::t.

Referenced by pause().

                        {
  if(0==--m_pauseCount) {
    tbb::task* t = pickNextTask();
    if(nullptr != t) {
      tbb::task::spawn(*t);
    }
    return true;
  }
  return false;
}

Friends And Related Function Documentation

friend class TaskBase

friend

Definition at line 168 of file SerialTaskQueue.h.

Member Data Documentation

std::atomic<unsigned long> edm::SerialTaskQueue::m_pauseCount

private

Definition at line 182 of file SerialTaskQueue.h.

Referenced by isPaused(), pause(), pickNextTask(), and resume().

std::atomic<bool> edm::SerialTaskQueue::m_taskChosen

private

Definition at line 181 of file SerialTaskQueue.h.

Referenced by finishedTask(), pickNextTask(), and ~SerialTaskQueue().

tbb::concurrent_queue<TaskBase*> edm::SerialTaskQueue::m_tasks

private

Definition at line 180 of file SerialTaskQueue.h.

Referenced by pickNextTask(), pushAndGetNextTask(), and ~SerialTaskQueue().