C ++ 11应用程序使用dispatch_apply不能在Mac OS Sierra下工作 [英] C++11 app that uses dispatch_apply not working under Mac OS Sierra

问题描述

我有一个用C ++ 11编写的完全功能的代码库，它使用了Grand Central Dispatch并行处理，特别是 dispatch_apply 为一些琐碎的游戏计算做了基本的并行循环。

I had a completely functioning codebase written in C++11 that used Grand Central Dispatch parallel processing, specifically dispatch_apply to do the basic parallel for loop for some trivial game calculations.

自从升级到Sierra之后，该代码仍然运行，但每个块都是以串行方式运行的， cout 语句表明它们是以串行顺序执行的， CPU使用情况图表不显示并行处理。

Since upgrading to Sierra, this code still runs, but each block is run in serial -- the cout statement shows that they are being executed in serial order, and CPU usage graph shows no parallel working on.

队列定义为：

workQueue = dispatch_queue_create("workQueue", DISPATCH_QUEUE_CONCURRENT);

相关程序代码为：

            case Concurrency::Parallel: {
                    dispatch_apply(stateMap.size(), workQueue, ^(size_t stateIndex) {
                        string thisCode = stateCodes[stateIndex];
                        long thisCount = stateCounts[stateIndex];

                        GameResult sliceResult = playStateOfCode(thisCode, thisCount);
                        results[stateIndex] = sliceResult;

                        if ((stateIndex + 1) % updatePeriod == 0) {
                            cout << stateIndex << endl;
                        }
                    });
                    break;
                }

我强烈怀疑这是一个错误，但如果这是GCD强迫我为了使用新的C ++方法，我很抱歉。

I strongly suspect that this either a bug, but if this is GCD forcing me to use new C++ methods for this, I'm all ears.

推荐答案

我不知道这是否是一个错误塞拉或不。但是，如果您显式将全局并行队列作为目标关联，它似乎工作。

I'm not sure if it is a bug in Sierra or not. But it seems to work if you explicitly associate a global concurrent queue as target:

dispatch_queue_t target =
        dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0);
dispatch_queue_t workQueue = 
        dispatch_queue_create_with_target("workQueue", DISPATCH_QUEUE_CONCURRENT, target);
//                            ^~~~~~~~~~~                                         ^~~~~~

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