《UE4游戏开发》之《了解UE4提供的并行函数接口》

最新推荐文章于 2025-01-08 14:41:32 发布

FLYINGSNOWGO

最新推荐文章于 2025-01-08 14:41:32 发布

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本文链接：https://blog.youkuaiyun.com/qq_21919621/article/details/115699608

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源码位置：Engine\Source\Runtime\Core\Public\Async\ParallelFor.h
源码声明：

/** 
	*	General purpose parallel for that uses the taskgraph
	*	@param Num; number of calls of Body; Body(0), Body(1)....Body(Num - 1)
	*	@param Body; Function to call from multiple threads
	*	@param bForceSingleThread; Mostly used for testing, if true, run single threaded instead.
	*	Notes: Please add stats around to calls to parallel for and within your lambda as appropriate. Do not clog the task graph with long running tasks or tasks that block.
**/
inline void ParallelFor(int32 Num, TFunctionRef<void(int32)> Body, bool bForceSingleThread, bool bPumpRenderingThread=false)
{
	ParallelForImpl::ParallelForInternal(Num, Body,
		(bForceSingleThread ? EParallelForFlags::ForceSingleThread : EParallelForFlags::None) | 
		(bPumpRenderingThread ? EParallelForFlags::PumpRenderingThread : EParallelForFlags::None));
}

使用示例：

void ClearAllPublicExportsLoaded(const TArray<FPackageId>& PackageIds)
	{
		int32 PackageCount = PackageIds.Num();
		bool bForceSingleThreaded = PackageCount < 1024;
		/**
			*当PackageCount的数量低于1024时，使用单线程
			*对于ParallelFor，在这里调用函数体的次数为PackageCount次
			*每次调用函数体是单线程运行还是多线程，由bForceSingleThreaded决定
		*/
		ParallelFor(PackageCount, [this, &PackageIds](int32 Index)
		{
			if (FLoadedPackageRef* PackageRef = LoadedPackageStore.FindPackageRef(PackageIds[Index]))
			{
				PackageRef->ClearAllPublicExportsLoaded();
			}
		}, bForceSingleThreaded);
	}