// 2019/02/15 - modified by Tsung-Wei Huang
//  - refactored the code
//
// 2019/01/03 - created by Chun-Xun Lin
//  - use dynamic tasking to implement graph traversal

#include   
#include 
#include 
#include 

struct Node {

  size_t level {0};
  bool visited {false};

  std::atomic dependents {0};
  std::vector successors;

  void precede(Node& n) {
    successors.emplace_back(&n);
    n.dependents ++;
  }
};


void traverse(Node* n, tf::SubflowBuilder& subflow) {
  assert(!n->visited);
  n->visited = true;
  for(size_t i=0; isuccessors.size(); i++) {
    if(--(n->successors[i]->dependents) == 0) {
      n->successors[i]->level = n->level + 1;
      subflow.emplace([s=n->successors[i]](tf::SubflowBuilder &subflow){ 
        traverse(s, subflow); 
      });
    }
  }
}

void sequential_traversal(std::vector& src) {
  auto start = std::chrono::system_clock::now();
  while(!src.empty()) {
    auto n = src.back();
    assert(!n->visited);
    n->visited = true;
    src.pop_back();
    for(auto& s: n->successors) {
      if(--s->dependents == 0) {
        s->level = n->level + 1;
        src.emplace_back(s);
      }
    }
  }
  auto end = std::chrono::system_clock::now();
  std::cout