c – 使用线程池进行模拟：boost-thread和boost-asio

分布式仿真基于使用两个实现类的主类DistributedSimulation：impl :: m_io_service和impl :: dispatcher.

boost :: asio线程池基于将io_service :: run()方法附加到不同的线程.
我们的想法是重新定义此方法并包含一种识别当前线程的机制.下面的解决方案基于boost :: uuid的线程本地存储boost :: thread_specific_ptr.在阅读了Tres的评论之后,我认为使用boost :: thread :: id识别线程是一个更好的解决方案(但是等效且不太不同).
最后,另一个类用于将输入数据分派给类Simulation的实例.此类创建同一类Simulation的多个实例,并使用它们计算每个线程中的结果.

namespace impl {

  // Create a derived class of io_service including thread specific data (a unique identifier of the thread)
  struct m_io_service : public boost::asio::io_service
  {
    static boost::thread_specific_ptr<boost::uuids::uuid> ptrSpec_;

    std::size_t run()
    {
      if(ptrSpec_.get() == 0) 
        ptrSpec_.reset(new boost::uuids::uuid(boost::uuids::random_generator()())  );

      return boost::asio::io_service::run();
    }
  };


  // Create a class that dispatches the input data over the N instances of the class Simulation
  template <class Simulation>
  class dispatcher
  {  
    public:
      static const std::size_t N = 6;

      typedef Simulation::input_t input_t;
      typedef Simulation::output_t output_t;

      friend DistributedSimulation;

    protected:
      std::vector< boost::shared_ptr<Simulation> > simuInst;
      std::vector< boost::uuids::uuid >            map;

    public:

      // Constructor,creating the N instances of class Simulation
      dispatcher( const Simulation& simuRef) 
      {
        simuInst.resize(N);
        for(std::size_t i=0; i<N; ++i)
          simuInst[i].reset( simuRef.clone() );
      }

      // Record the unique identifiers and do the calculation using the right instance of class Simulation
      void dispatch( const Simulation::input_t& in  )
      {
        if( map.size() == 0 ) {
          map.push_back(*m_io_service::ptrSpec_);
          simuInst[0]->eval(in,*m_io_service::ptrSpec_);
        }    
        else {
          if( map.size() < N ) {
            map.push_back(*m_io_service::ptrSpec_);
            simuInst[map.size()-1]->eval(in,*m_io_service::ptrSpec_);
          }
          else {
            for(size_t i=0; i<N;++i) {
              if( map[i] == *m_io_service::ptrSpec_) {
                simuInst[i]->eval(in,*m_io_service::ptrSpec_);
                return;
              }
            }
          }
        }
      }
  };

  boost::thread_specific_ptr<boost::uuids::uuid> m_io_service::ptrSpec_;
}


  // Main class,create a distributed simulation based on a class Simulation
  template <class Simulation>
  class DistributedSimulation
  {
  public:
    static const std::size_t N = impl::dispatcher::N;

  protected: 
    impl::dispatcher _disp;

  public:
    DistributedSimulation() : _disp( Simulation() ) {}

    DistributedSimulation(Simulation& simuRef) 
    : _disp( simuRef ) {  }


    // Simulation with a large (>>N) number of inputs
    void eval( const std::vector< Simulation::input_t >& inputs,std::vector< Simulation::output_t >& outputs )
    {

      // Clear the results from a previous calculation (and stored in instances of class Simulation)
      ...

      // Creation of the pool using N threads
      impl::m_io_service io_service;
      boost::asio::io_service::work work(io_service);
      boost::thread_group threads;
      for (std::size_t i = 0; i < N; ++i)
        threads.create_thread(boost::bind(&impl::m_io_service::run,&io_service));

      // Adding tasks
      for( std::size_t i = 0,i_end = inputs.size(); i<i_end; ++i)
        io_service.post( boost::bind(&impl::dispatcher::dispatch,&_disp,inputs[i]) );

      // End of the tasks
      io_service.stop();
      threads.join_all();

      // Gather the results iterating through instances of class simulation
      ...
    }
  };

编辑

下面的代码是我之前的解决方案的更新,考虑到Tres的评论.正如我之前所说,它更易读！

template <class Simulation>
  class DistributedSimulation
  {
    public:
      typedef typename Simulation::input_t  input_t;
      typedef typename Simulation::output_t output_t;

      typedef boost::shared_ptr<Simulation> SimulationSPtr_t;
      typedef boost::thread::id             id_t;      
      typedef std::map< id_t,std::size_t >::iterator IDMapIterator_t;

    protected: 
      unsigned int                    _NThreads;   // Number of threads
      std::vector< SimulationSPtr_t > _simuInst;   // Instances of class Simulation
      std::map< id_t,std::size_t >   _IDMap;      // Map between thread id and instance index.

    private:
      boost::mutex _mutex;

    public:

      DistributedSimulation(  ) {}

      DistributedSimulation( const Simulation& simuRef,const unsigned int NThreads = boost::thread::hardware_concurrency() ) 
        { init(simuRef,NThreads); }

      DistributedSimulation(const DistributedSimulation& simuDistrib) 
        { init(simuRef,NThreads); }

      virtual ~DistributedSimulation() {}

      void init(const Simulation& simuRef,const unsigned int NThreads = boost::thread::hardware_concurrency())
      {
        _NThreads = (NThreads == 0) ? 1 : NThreads;
        _simuInst.resize(_NThreads);
        for(std::size_t i=0; i<_NThreads; ++i)
          _simuInst[i].reset( simuRef.clone() );
        _IDMap.clear();
      }


      void dispatch( const input_t& input )
      {
        // Get current thread id
        boost::thread::id id0 = boost::this_thread::get_id();

        // Get the right instance 
        Simulation* sim = NULL;        
        { 
          boost::mutex::scoped_lock scoped_lock(_mutex);
          IDMapIterator_t it = _IDMap.find(id0);
          if( it != _IDMap.end() )
            sim = _simuInst[it->second].get();
        } 

        // Simulation
        if( NULL != sim )
          sim->eval(input);
      }


      // Distributed evaluation.
      void eval( const std::vector< input_t >& inputs,std::vector< output_t >& outputs )
      {
        //--Initialisation
        const std::size_t NInputs = inputs.size();

        // Clear the ouptuts f(contained in instances of class Simulation) from a previous run
        ...

        // Create thread pool and save ids
        boost::asio::io_service io_service;
        boost::asio::io_service::work work(io_service);
        boost::thread_group threads;
        for (std::size_t i = 0; i < _NThreads; ++i)
        {
          boost::thread* thread_ptr = threads.create_thread(boost::bind(&boost::asio::io_service::run,&io_service));
          _IDMap[ thread_ptr->get_id() ] = i;
        }

        // Add tasks
        for( std::size_t i = 0; i < NInputs; ++i)
          io_service.post( boost::bind(&DistributedSimulation::dispatch,this,inputs[i]) );

        // Stop the service
        io_service.stop();
        threads.join_all();

        // Gather results (contained in each instances of class Simulation)
        ...
      }
  };