为什么我会出现种族状况

Question

我正在尝试将多个CGAL网格合并为一个几何体。

我有下面的顺序代码，工作非常好：

while (m_toCombine.size() > 1) {
auto mesh1 = m_toCombine.front();
m_toCombine.pop_front();
auto mesh2 = m_toCombine.front();
m_toCombine.pop_front();
bool result = CGAL::Polygon_mesh_processing::corefine_and_compute_union(mesh1, mesh2, mesh2);
m_toCombine.push_back(mesh2);
}

其中，m_toCombine是std::list<Triangle_mesh_exact>。

Triangle_mesh_exact是CGAL网格(三角多面体几何(的一种。但我不认为这真的与这个问题有关。

不幸的是，这个过程对于我想要的应用程序来说太慢了，所以我决定使用"；分而治之；概念并以并行方式组合网格：

class Combiner
{
public:
Combiner(const std::list<Triangle_mesh_exact>& toCombine) :
m_toCombine(toCombine) {};
~Combiner() {};
Triangle_mesh_exact combineMeshes();
void combineMeshes2();
private:
std::mutex m_listMutex, m_threadListMutex;
std::mutex m_eventLock;
std::list<MiniThread> m_threads;
std::list<Triangle_mesh_exact> m_toCombine;
std::condition_variable m_eventSignal;
std::atomic<bool> m_done = false;
//void poll(int threadListIndex);
};

Triangle_mesh_exact Combiner::combineMeshes()
{
std::unique_lock<std::mutex> uniqueLock(m_eventLock, std::defer_lock);
int runningCount = 0, finishedCount = 0;
int toCombineCount = m_toCombine.size();
bool stillRunning = false;
bool stillCombining = true;
while (stillCombining || stillRunning) {
uniqueLock.lock();
//std::lock_guard<std::mutex> lock(m_listMutex);
m_listMutex.lock();
Triangle_mesh_exact mesh1 = std::move(m_toCombine.front());
m_toCombine.pop_front();
toCombineCount--;
Triangle_mesh_exact mesh2 = std::move(m_toCombine.front());
m_toCombine.pop_front();
toCombineCount--;
m_listMutex.unlock();
runningCount++;
auto thread = new std::thread([&, this, mesh1, mesh2]() mutable {
//m_listMutex.lock();
CGAL::Polygon_mesh_processing::corefine_and_compute_union(mesh1, mesh2, mesh2);

std::lock_guard<std::mutex> lock(m_listMutex);
m_toCombine.push_back(mesh2);
toCombineCount++;
finishedCount++;
m_eventSignal.notify_one();
//m_listMutex.unlock();
});
thread->detach();

while (toCombineCount < 2 && runningCount != finishedCount) {
m_eventSignal.wait(uniqueLock);
}
stillRunning = runningCount != finishedCount;
stillCombining = toCombineCount >= 2;
uniqueLock.unlock();
}

return m_toCombine.front();
}

不幸的是，尽管格外小心，我还是会遇到内存访问冲突或与mesh1或mesh2析构函数相关的错误的崩溃。

我是不是错过了什么？

Answer 1

使标准库的检查能力变得复杂：

std:：reduce-cppreference.com

Triangle_mesh_exact combine(Triangle_mesh_exact& a, Triangle_mesh_exact& b)
{
auto success = CGAL::Polygon_mesh_processing::corefine_and_compute_union(a, b, b);
if (!success) throw my_combine_exception{};
return b;
}
Triangle_mesh_exact combineAll()
{
if (m_toCombine.size() == 1) return m_toCombine.front();
if (m_toCombine.empty()) throw std::invalid_argument("");
return std::reduce(std::execution::par,
m_toCombine.begin() + 1, m_toCombine.end(), 
m_toCombine.front(), combine);
}