[英]How do I wait for all other threads to finish their tasks?
我有幾個線程使用與下面的代碼類似的東西來消耗隊列中的任務。 問題在於,有一種類型的任務在處理任何其他任務時無法運行。
這是我所擁有的:
while (true) // Threaded code
{
while (true)
{
lock(locker)
{
if (close_thread)
return;
task = GetNextTask(); // Get the next task from the queue
}
if (task != null)
break;
wh.WaitOne(); // Wait until a task is added to the queue
}
task.Run();
}
這就是我所需要的:
while (true)
{
while (true)
{
lock(locker)
{
if (close_thread)
return;
if (disable_new_tasks)
{
task = null;
}
else
{
task = GetNextTask();
}
}
if (task != null)
break;
wh.WaitOne();
}
if(!task.IsThreadSafe())
{
// I would set this to false inside task.Run() at
// the end of the non-thread safe task
disable_new_tasks = true;
Wait_for_all_threads_to_finish_their_current_tasks();
}
task.Run();
}
問題是我不知道如何在不造成混亂的情況下實現這一目標。
嘗試使用TreadPool,然后使用WaitHandle.WaitAll方法確定所有線程均已完成執行。
WaitHandle.WaitAll(autoEvents); 也許這就是您想要的。
class Calculate
{
double baseNumber, firstTerm, secondTerm, thirdTerm;
AutoResetEvent[] autoEvents;
ManualResetEvent manualEvent;
// Generate random numbers to simulate the actual calculations.
Random randomGenerator;
public Calculate()
{
autoEvents = new AutoResetEvent[]
{
new AutoResetEvent(false),
new AutoResetEvent(false),
new AutoResetEvent(false)
};
manualEvent = new ManualResetEvent(false);
}
void CalculateBase(object stateInfo)
{
baseNumber = randomGenerator.NextDouble();
// Signal that baseNumber is ready.
manualEvent.Set();
}
// The following CalculateX methods all perform the same
// series of steps as commented in CalculateFirstTerm.
void CalculateFirstTerm(object stateInfo)
{
// Perform a precalculation.
double preCalc = randomGenerator.NextDouble();
// Wait for baseNumber to be calculated.
manualEvent.WaitOne();
// Calculate the first term from preCalc and baseNumber.
firstTerm = preCalc * baseNumber *
randomGenerator.NextDouble();
// Signal that the calculation is finished.
autoEvents[0].Set();
}
void CalculateSecondTerm(object stateInfo)
{
double preCalc = randomGenerator.NextDouble();
manualEvent.WaitOne();
secondTerm = preCalc * baseNumber *
randomGenerator.NextDouble();
autoEvents[1].Set();
}
void CalculateThirdTerm(object stateInfo)
{
double preCalc = randomGenerator.NextDouble();
manualEvent.WaitOne();
thirdTerm = preCalc * baseNumber *
randomGenerator.NextDouble();
autoEvents[2].Set();
}
public double Result(int seed)
{
randomGenerator = new Random(seed);
// Simultaneously calculate the terms.
ThreadPool.QueueUserWorkItem(
new WaitCallback(CalculateBase));
ThreadPool.QueueUserWorkItem(
new WaitCallback(CalculateFirstTerm));
ThreadPool.QueueUserWorkItem(
new WaitCallback(CalculateSecondTerm));
ThreadPool.QueueUserWorkItem(
new WaitCallback(CalculateThirdTerm));
// Wait for all of the terms to be calculated.
**WaitHandle.WaitAll(autoEvents);**
// Reset the wait handle for the next calculation.
manualEvent.Reset();
return firstTerm + secondTerm + thirdTerm;
}
}
您可以認為這類似於允許任意數量的讀取器或一個寫入器的數據結構。 也就是說,任何數量的線程都可以讀取數據結構,但是寫入數據結構的線程需要互斥訪問。
在您的情況下,您可以運行任意數量的“常規”線程,也可以有一個需要獨占訪問的線程。
.NET具有ReaderWriterLock
和ReaderWriterLockSlim
類,您可以使用它們來實現這種共享。 不幸的是,這兩個類都不在xbox上可用。
但是,可以通過Monitor
和ManualResetEvent
對象的組合來實現讀取器/寫入器鎖定。 我沒有C#示例(為什么可以,因為我可以訪問本機對象?),但是有一個簡單的Win32實現 ,移植起來應該不難。
你可以用這樣的東西
ExecutorService workers = Executors.newFixedThreadPool(10);
for(int i=0; i<input.length; i++) {
Teste task = new Teste(rowArray,max);//your thread class
workers.execute(task);
}
workers.shutdown();//ask for shut down
while(!workers.isTerminated()) {//wait until all finishes.
try {
Thread.sleep(100);//
} catch (InterruptedException exception) {
}
System.out.println("waiting for submitted task to finish operation");
}
希望能有所幫助。
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