关键字:UE4 多线程
原文:https://wiki.unrealengine.com/Multi-Threading:_How_to_Create_Threads_in_UE4
相关文档
FRunnable
https://docs.unrealengine.com/latest/INT/API/Runtime/Core/HAL/FRunnable/index.html
FRunnableThread
https://docs.unrealengine.com/latest/INT/API/Runtime/Core/HAL/FRunnableThread/index.html
h头文件:
//~~~~~ Multi Threading ~~~ class FPrimeNumberWorker : public FRunnable { /** Singleton instance, can access the thread any time via static accessor, if it is active! */ static FPrimeNumberWorker* Runnable; /** Thread to run the worker FRunnable on */ FRunnableThread* Thread; /** The Data Ptr */ TArray<uint32>* PrimeNumbers; /** The PC */ AVictoryGamePlayerController* ThePC; /** Stop this thread? Uses Thread Safe Counter */ FThreadSafeCounter StopTaskCounter; //The actual finding of prime numbers int32 FindNextPrimeNumber(); private: int32 PrimesFoundCount; public: int32 TotalPrimesToFind; //Done? bool IsFinished() const { return PrimesFoundCount >= TotalPrimesToFind; } //~~~ Thread Core Functions ~~~ //Constructor / Destructor FPrimeNumberWorker(TArray<uint32>& TheArray, const int32 IN_PrimesToFindPerTick, AVictoryGamePlayerController* IN_PC); virtual ~FPrimeNumberWorker(); // Begin FRunnable interface. virtual bool Init(); virtual uint32 Run(); virtual void Stop(); // End FRunnable interface /** Makes sure this thread has stopped properly */ void EnsureCompletion(); //~~~ Starting and Stopping Thread ~~~ /* Start the thread and the worker from static (easy access)! This code ensures only 1 Prime Number thread will be able to run at a time. This function returns a handle to the newly started instance. */ static FPrimeNumberWorker* JoyInit(TArray<uint32>& TheArray, const int32 IN_TotalPrimesToFind, AVictoryGamePlayerController* IN_PC); /** Shuts down the thread. Static so it can easily be called from outside the thread context */ static void Shutdown(); static bool IsThreadFinished(); };
cpp文件:
//*********************************************************** //Thread Worker Starts as NULL, prior to being instanced // This line is essential! Compiler error without it FPrimeNumberWorker* FPrimeNumberWorker::Runnable = NULL; //*********************************************************** FPrimeNumberWorker::FPrimeNumberWorker(TArray<uint32>& TheArray, const int32 IN_TotalPrimesToFind, AVictoryGamePlayerController* IN_PC) : ThePC(IN_PC) , TotalPrimesToFind(IN_TotalPrimesToFind) , StopTaskCounter(0) , PrimesFoundCount(0) { //Link to where data should be stored PrimeNumbers = &TheArray; Thread = FRunnableThread::Create(this, TEXT("FPrimeNumberWorker"), 0, TPri_BelowNormal); //windows default = 8mb for thread, could specify more } FPrimeNumberWorker::~FPrimeNumberWorker() { delete Thread; Thread = NULL; } //Init bool FPrimeNumberWorker::Init() { //Init the Data PrimeNumbers->Empty(); PrimeNumbers->Add(2); PrimeNumbers->Add(3); if(ThePC) { ThePC->ClientMessage("**********************************"); ThePC->ClientMessage("Prime Number Thread Started!"); ThePC->ClientMessage("**********************************"); } return true; } //Run uint32 FPrimeNumberWorker::Run() { //Initial wait before starting FPlatformProcess::Sleep(0.03); //While not told to stop this thread // and not yet finished finding Prime Numbers while (StopTaskCounter.GetValue() == 0 && ! IsFinished()) { PrimeNumbers->Add(FindNextPrimeNumber()); PrimesFoundCount++; //*************************************** //Show Incremental Results in Main Game Thread! // Please note you should not create, destroy, or modify UObjects here. // Do those sort of things after all thread are completed. // All calcs for making stuff can be done in the threads // But the actual making/modifying of the UObjects should be done in main game thread. ThePC->ClientMessage(FString::FromInt(PrimeNumbers->Last())); //*************************************** //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //prevent thread from using too many resources //FPlatformProcess::Sleep(0.01); //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ } //Run FPrimeNumberWorker::Shutdown() from the timer in Game Thread that is watching //to see when FPrimeNumberWorker::IsThreadFinished() return 0; } //stop void FPrimeNumberWorker::Stop() { StopTaskCounter.Increment(); } FPrimeNumberWorker* FPrimeNumberWorker::JoyInit(TArray<uint32>& TheArray, const int32 IN_TotalPrimesToFind, AVictoryGamePlayerController* IN_PC) { //Create new instance of thread if it does not exist // and the platform supports multi threading! if (!Runnable && FPlatformProcess::SupportsMultithreading()) { Runnable = new FPrimeNumberWorker(TheArray,IN_TotalPrimesToFind,IN_PC); } return Runnable; } void FPrimeNumberWorker::EnsureCompletion() { Stop(); Thread->WaitForCompletion(); } void FPrimeNumberWorker::Shutdown() { if (Runnable) { Runnable->EnsureCompletion(); delete Runnable; Runnable = NULL; } } bool FPrimeNumberWorker::IsThreadFinished() { if(Runnable) return Runnable->IsFinished(); return true; } int32 FPrimeNumberWorker::FindNextPrimeNumber() { //Last known prime number + 1 int32 TestPrime = PrimeNumbers->Last(); bool NumIsPrime = false; while( ! NumIsPrime) { NumIsPrime = true; //Try Next Number TestPrime++; //Modulus from 2 to current number - 1 for(int32 b = 2; b < TestPrime; b++) { //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //prevent thread from using too many resources //FPlatformProcess::Sleep(0.01); //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ if(TestPrime % b == 0) { NumIsPrime = false; break; //~~~ } } } //Success! return TestPrime; }
以上是完成了一个继承自FRunnable的自定义类,那么如何用这个类启动线程:
1,这个例子需要一个数组,那么现在头文件中定义一个测试用的变量
//In the .h for the player controller // this is the actual data TArray<uint32> PrimeNumbers;
2,创建并启动线程:
//player controller .cpp //Multi-threading, returns handle that could be cached. // use static function FPrimeNumberWorker::Shutdown() if necessary FPrimeNumberWorker::JoyInit(PrimeNumbers, 50000, this);
补充:
结束终止线程
void FPrimeNumberWorker::EnsureCompletion() { Stop(); Thread->WaitForCompletion(); }