DepGraphNode.hpp

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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~//
// Copyright (c) Lawrence Livermore National Security, LLC and other
// RAJA Project Developers. See top-level LICENSE and COPYRIGHT
// files for dates and other details. No copyright assignment is required
// to contribute to RAJA.
//
// SPDX-License-Identifier: (BSD-3-Clause)
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~//
 
#ifndef RAJA_DepGraphNode_HPP
#define RAJA_DepGraphNode_HPP
 
#include "RAJA/config.hpp"
 
#include <atomic>
#include <cstdlib>
#include <iosfwd>
#include <thread>
 
#include "RAJA/util/types.hpp"
 
namespace RAJA
{
 
class RAJA_ALIGNED_ATTR(256) DepGraphNode
{
public:
  static const int _MaxDepTasks_ = 8;
 
  DepGraphNode()
      : m_num_dep_tasks(0),
        m_semaphore_reload_value(0),
        m_semaphore_value(0)
  {}
 
  std::atomic<int>& semaphoreValue() { return m_semaphore_value; }
 
  int& semaphoreReloadValue() { return m_semaphore_reload_value; }
 
  void reset() { m_semaphore_value.store(m_semaphore_reload_value); }
 
  void satisfyOne()
  {
    if (m_semaphore_value > 0)
    {
      --m_semaphore_value;
    }
  }
 
  void wait()
  {
    while (m_semaphore_value > 0)
    {
      // TODO: an efficient wait would be better here, but the standard
      // promise/future is not good enough
      std::this_thread::yield();
    }
  }
 
  int& numDepTasks() { return m_num_dep_tasks; }
 
  int& depTaskNum(int tidx) { return m_dep_task[tidx]; }
 
  void print(std::ostream& os) const;
 
private:
  int m_dep_task[_MaxDepTasks_];
  int m_num_dep_tasks;
  int m_semaphore_reload_value;
  std::atomic<int> m_semaphore_value;
};
 
}  // namespace RAJA
 
#endif  // closing endif for header file include guard