c++ - C++ 中发送者-接收者模型中的多线程

Question

我正在尝试用 C++ 构建一个发送者-接收者模型。我想以前馈方式将数据从发送方发送到接收方。简而言之，所需的架构可以这样表示(基本单元称为节点):

Each node can receive (send) data from (to) another node. Each node has as many as desired senders (receivers). Each node has a number called impulse which is data supposed to be sent. Let's call one data propagation through a whole network a cycle. Then in one cycle each node that belongs to the network must send impulse once and only once to all its receivers.

下面是上述想法的初步实现。

class Node
{
  private :
    double in_signal;//received data
    double out_signal;//data to send
    bool is_opened;//status of channel

    void update_in( double package );//receive new package

  protected :
    std::vector<Node*> receivers;

  public :
    Node( double out_signal )
    : in_signal(0.),
      out_signal(out_signal),
      is_opened(false)
    {}
    ~Node() {}

    void add_receiver( Node* receiver );
    void emit();//send out_signal or impulse
};

void Node::update_in( double package )
{
  //the problem is how to control the status of the channel:
  //it must be closed after getting all data
  if ( not is_opened )
  {
    in_signal = 0.;//reset
    is_opened = true;
  }
  in_signal += package;
}

void Node::add_receiver( Node* receiver )
{
   receivers.push_back( receiver );
}

void Node::emit()
{
   for ( auto& receiver : receivers )
   {
      receiver->update_in( out_signal );
   }
} 

我无法解决的问题是这个架构背后的多线程:

The node's in_signal can be updated by several senders, but senders work independently (required) therefore I am afraid of arising concurrency.

---

所以我想问一下

1. 如何解决这个多读问题？
2. 如何确定是否已收到所有数据？

我会感谢一些想法、模式、概念等。

Answer 1

首先，恕我直言，这是对您的问题的过度简化。我认为，例如，您的数据不能简单地是 double。

无论如何:

1. 如果在您的架构中存在竞争条件(如果每个节点都有自己的线程，那么您显然存在竞争条件)，除了mutex，我看不到任何解决方案。
2. 这取决于实际任务的庞大性和复杂性，但您可以应用一些规则让节点能够理解数据包的生命周期(一些想法:数据包的序列号、近节点列表等)。