c++ - 如何使用多线程 C++ 在循环中启动多个操作

Question

介绍

我正在尝试并行启动 4 个函数:func1, func2, func3和 func4在 6 上芯机。每个函数将迭代 1000 次填充 vector 实体。主要功能是do_operations() .我有两个版本的 do_operations()我在源代码部分发布了它。

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问题

通过使用第一个版本，我得到以下错误:

std::system_error'
what():  Resource temporarily unavailable

为了解决这个问题。我在 version 2 中添加了条件.如果线程数等于 6，这是我拥有的核心数。然后我运行线程并清除 vector<thread> threads .

我是否正确编写了线程函数？我做错了什么。

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源代码

void my_class::func1(std::vector<std::string> & entities)
{
  for(int = 0; i < 1000;i++)
  {
      mtx.lock();
      entities.push_back(to_string(i));
      mtx.unlock();
  }
}

void my_class::func2(std::vector<std::string> & entities)
{
  for(int = 0; i < 1000;i++)
  {
      mtx.lock();
      entities.push_back(to_string(i));
      mtx.unlock();
  }
}


void my_class::func3(std::vector<std::string> & entities)
{
  for(int = 0; i < 1000;i++)
  {
      mtx.lock();
      entities.push_back(to_string(i));
      mtx.unlock();
  }
}

void my_class::func4(std::vector<std::string> & entities)
{  
  for(int = 0; i < 1000;i++)
  {
      mtx.lock();
      entities.push_back(to_string(i));
      mtx.unlock();
  }
}

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版本 1

void my_class::do_operations()
{
   //get number of CPUS 
   int concurentThreadsSupported = std::thread::hardware_concurrency();
   std::vector<std::thread> threads; 
   std::vector<std::string> entities;
    for(int i =0; i < 1000; i++)
    {
        threads.push_back(std::thread(&my_class::func1, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func2, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func3, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func4, this, ref(entities)));
    }
    
    for(auto &t : threads){ t.join(); }
    threads.clear();
}

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版本 2

void my_class::do_operations()
{
   //get number of CPUS 
   int concurentThreadsSupported = std::thread::hardware_concurrency();
   std::vector<std::thread> threads; 
   std::vector<std::string> entities;
    for(int i =0; i < 1000; i++)
    {
        threads.push_back(std::thread(&my_class::func1, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func2, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func3, this, ref(entities)));
        threads.push_back(std::thread(&my_class::func4, this, ref(entities)));
        
          if((threads.size() == concurentThreadsSupported) || (i == 999))
          {
               for(auto &t : threads){ t.join(); }
              threads.clear();
          }
    }
}

Answer 1

您总共启动了 4000 个线程。如果每个线程获得1MB的堆栈空间，那么只有线程会占用4000MB的地址空间。我的假设是您没有为应用程序保留完整的 4GB 32 位地址空间(必须为内核和硬件保留一些空间)。我的第二个假设是，如果没有足够的空间来分配新堆栈，它将返回您看到的消息。