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// 2019/04/09 - modified by Tsung-Wei Huang
//  - removed silent_dispatch method
// 2019/03/12 - modified by Chun-Xun Lin
//  - added framework
// 2019/02/11 - modified by Tsung-Wei Huang
//  - refactored run_until
//  - added allocator to topologies
//  - changed to list for topologies
// 2019/02/10 - modified by Chun-Xun Lin
//  - added run_n to execute framework
//  - finished first peer-review with TW
// 2018/07 - 2019/02/09 - missing logs
// 2018/06/30 - created by Tsung-Wei Huang
//  - added BasicTaskflow template
// TODO items:
// 1. come up with a better way to remove the "joined" links 
//    during the execution of a static node (1st layer)
#pragma once
#include "topology.hpp"
namespace tf {
/** @class BasicTaskflow
@brief The base class to derive a taskflow class.
@tparam E: executor type to use in this taskflow
This class is the base class to derive a taskflow class. 
It inherits all public methods to create tasks from tf::FlowBuilder
and defines means to execute task dependency graphs.
template <template <typename...> typename E>
class BasicTaskflow : public FlowBuilder {
  using StaticWork  = typename Node::StaticWork;
  using DynamicWork = typename Node::DynamicWork;
  struct Closure {
    friend class BasicTaskflow;
    Closure() = default;
    Closure(const Closure&) = default;
    Closure(BasicTaskflow&, Node&);
    Closure& operator = (const Closure&) = default;
    void operator ()() const;
    BasicTaskflow* taskflow {nullptr};
    Node*          node     {nullptr};
  @typedef Executor
  @brief alias of executor type
  using Executor = E<Closure>;
    @brief constructs the taskflow with std::thread::hardware_concurrency worker threads
    explicit BasicTaskflow();
    @brief constructs the taskflow with N worker threads
    explicit BasicTaskflow(unsigned N);
    @brief constructs the taskflow with a given executor
    explicit BasicTaskflow(std::shared_ptr<Executor> executor);
    @brief destructs the taskflow
    Destructing a taskflow object will first wait for all running topologies to finish
    and then clean up all associated data storages.
    ~BasicTaskflow();
    @brief shares ownership of the executor associated with this taskflow object
    @return a std::shared_ptr of the executor
    std::shared_ptr<Executor> share_executor();
    @brief dispatches the present graph to threads and returns immediately
    @return a std::shared_future to access the execution status of the dispatched graph
    std::shared_future<void> dispatch();
    @brief dispatches the present graph to threads and run a callback when the graph completes
    @return a std::shared_future to access the execution status of the dispatched graph
    template <typename C>
    std::shared_future<void> dispatch(C&&);
    @brief dispatches the present graph to threads and wait for all topologies to complete
    void wait_for_all();
    @brief blocks until all running topologies complete and then
           cleans up all associated storages
    void wait_for_topologies();
    @brief dumps the present task dependency graph to a std::ostream in DOT format
    @param ostream a std::ostream target
    void dump(std::ostream& ostream) const;
    @brief dumps the present topologies to a std::ostream in DOT format
    @param ostream a std::ostream target
    void dump_topologies(std::ostream& ostream) const;
    @brief queries the number of nodes in the present task dependency graph
    size_t num_nodes() const;
    @brief queries the number of worker threads in the associated executor
    size_t num_workers() const;
    @brief queries the number of existing topologies
    size_t num_topologies() const;
    @brief dumps the present task dependency graph in DOT format to a std::string
    std::string dump() const;
    @brief dumps the existing topologies in DOT format to a std::string
    std::string dump_topologies() const;
    @brief runs the framework once
    @param framework a tf::Framework object
    @return a std::shared_future to access the execution status of the framework
    std::shared_future<void> run(Framework& framework);
    @brief runs the framework once and invoke a callback upon completion
    @param framework a tf::Framework object 
    @param callable a callable object to be invoked after this run
    @return a std::shared_future to access the execution status of the framework
    template<typename C>
    std::shared_future<void> run(Framework& framework, C&& callable);
    @brief runs the framework for N times
    @param framework a tf::Framework object
    @param N number of runs
    @return a std::shared_future to access the execution status of the framework
    std::shared_future<void> run_n(Framework& framework, size_t N);
    @brief runs the framework for N times and invokes a callback upon completion
    @param framework a tf::Framework 
    @param N number of runs
    @param callable a callable object to be invoked after this run
    @return a std::shared_future to access the execution status of the framework
    template<typename C>
    std::shared_future<void> run_n(Framework& framework, size_t N, C&& callable);
    @brief runs the framework multiple times until the predicate becomes true and invoke a callback
    @param framework a tf::Framework 
    @param predicate a boolean predicate to return true for stop
    @return a std::shared_future to access the execution status of the framework
    template<typename P>
    std::shared_future<void> run_until(Framework& framework, P&& predicate);
    @brief runs the framework multiple times until the predicate becomes true and invoke a callback
    @param framework a tf::Framework 
    @param predicate a boolean predicate to return true for stop
    @param callable a callable object to be invoked after this run
    @return a std::shared_future to access the execution status of the framework
    template<typename P, typename C>
    std::shared_future<void> run_until(Framework& framework, P&& predicate, C&& callable);
    Graph _graph;
    std::shared_ptr<Executor> _executor;
    std::list<Topology, SingularAllocator<Topology>> _topologies;
    void _schedule(Node&);
    void _schedule(PassiveVector<Node*>&);
    void _set_module_node(Node&);
// ============================================================================
// BasicTaskflow::Closure Method Definitions
// ============================================================================
// Function: run
template <template <typename...> typename E>
std::shared_future<void> BasicTaskflow<E>::run(Framework& f) {
  return run_n(f, 1, [](){});
// Function: run
template <template <typename...> typename E>
template <typename C>
std::shared_future<void> BasicTaskflow<E>::run(Framework& f, C&& c) {
  static_assert(std::is_invocable<C>::value);
  return run_n(f, 1, std::forward<C>(c));
// Function: run_n
template <template <typename...> typename E>
std::shared_future<void> BasicTaskflow<E>::run_n(Framework& f, size_t repeat) {
  return run_n(f, repeat, [](){});
// Function: run_n
template <template <typename...> typename E>
template <typename C>
std::shared_future<void> BasicTaskflow<E>::run_n(Framework& f, size_t repeat, C&& c) {
  return run_until(f, [repeat]() mutable { return repeat-- == 0; }, std::forward<C>(c));
// Function: run_until
template <template <typename...> typename E>
template <typename P>
std::shared_future<void> BasicTaskflow<E>::run_until(Framework& f, P&& predicate) {
  return run_until(f, std::forward<P>(predicate), [](){});
// Function: run_until
template <template <typename...> typename E>
template <typename P, typename C>
std::shared_future<void> BasicTaskflow<E>::run_until(Framework& f, P&& predicate, C&& c) {
  // Predicate must return a boolean value
  static_assert(std::is_invocable_v<C> && std::is_invocable_v<P>);
  if(std::invoke(predicate)) {
    return std::async(std::launch::deferred, [](){}).share();
  // create a topology for this run
  auto &tpg = _topologies.emplace_back(f, std::forward<P>(predicate));
  // Iterative execution to avoid stack overflow
  if(num_workers() == 0) {
    // Clear last execution data & Build precedence between nodes and target
    tpg._bind(f._graph);
      _schedule(tpg._sources);
      tpg._recover_num_sinks();
    } while(!std::invoke(tpg._predicate));
    std::invoke(c);
    tpg._promise.set_value();
    return tpg._future;
  // Multi-threaded execution.
  std::scoped_lock lock(f._mtx);
  f._topologies.push_back(&tpg);
  bool run_now = (f._topologies.size() == 1);
  if(run_now) {
    tpg._bind(f._graph);
  tpg._work = [&f, c=std::forward<C>(c), this] () mutable {
    // case 1: we still need to run the topology again
    if(!std::invoke(f._topologies.front()->_predicate)) {
      f._topologies.front()->_recover_num_sinks();
      _schedule(f._topologies.front()->_sources); 
    // case 2: the final run of this topology
      std::invoke(c);
      f._mtx.lock();
      // If there is another run (interleave between lock)
      if(f._topologies.size() > 1) {
        // Set the promise
        f._topologies.front()->_promise.set_value();
        f._topologies.pop_front();
        f._topologies.front()->_bind(f._graph);
        f._mtx.unlock();
        _schedule(f._topologies.front()->_sources);
      else {
        assert(f._topologies.size() == 1);
        // Need to back up the promise first here becuz framework might be 
        // destroy before taskflow leaves
        auto &p = f._topologies.front()->_promise; 
        f._topologies.pop_front();
        f._mtx.unlock();
        // We set the promise in the end in case framework leaves before taskflow
        p.set_value();
  if(run_now) {
    _schedule(tpg._sources);
  return tpg._future;
// Constructor
template <template <typename...> typename E>
BasicTaskflow<E>::Closure::Closure(BasicTaskflow& t, Node& n) : 
  taskflow{&t}, node {&n} {
// Operator ()
template <template <typename...> typename E>
void BasicTaskflow<E>::Closure::operator () () const {
  // Here we need to fetch the num_successors first to avoid the invalid memory
  // access caused by topology clear.
  const auto num_successors = node->num_successors();
  // regular node type
  // The default node work type. We only need to execute the callback if any.
  if(auto index=node->_work.index(); index == 0) {
    if(node->_module != nullptr) {
      bool first_time = !node->is_spawned();
      std::invoke(std::get<StaticWork>(node->_work));
      if(first_time) {
        return ;
      if(auto &f = std::get<StaticWork>(node->_work); f != nullptr){
        std::invoke(f);
  // subflow node type 
    // Clear the subgraph before the task execution
    if(!node->is_spawned()) {
      node->_subgraph.emplace();
    SubflowBuilder fb(*(node->_subgraph));
    std::invoke(std::get<DynamicWork>(node->_work), fb);
    // Need to create a subflow if first time & subgraph is not empty 
    if(!node->is_spawned()) {
      node->set_spawned();
      if(!node->_subgraph->empty()) {
        // For storing the source nodes
        PassiveVector<Node*> src; 
        for(auto& n : *(node->_subgraph)) {
          n._topology = node->_topology;
          n.set_subtask();
          if(n.num_successors() == 0) {
            if(fb.detached()) {
              node->_topology->_num_sinks ++;
            else {
              n.precede(*node);
          if(n.num_dependents() == 0) {
            src.push_back(&n);
        taskflow->_schedule(src);
        if(!fb.detached()) {
          return;
  } // End of DynamicWork -----------------------------------------------------
  // Recover the runtime change due to dynamic tasking except the target & spawn tasks 
  // This must be done before scheduling the successors, otherwise this might cause 
  // race condition on the _dependents
  //if(num_successors && !node->_subtask) {
  if(!node->is_subtask()) {
    // Only dynamic tasking needs to restore _dependents
    // TODO:
    if(node->_work.index() == 1 &&  !node->_subgraph->empty()) {
      while(!node->_dependents.empty() && node->_dependents.back()->is_subtask()) {
        node->_dependents.pop_back();
    node->_num_dependents = static_cast<int>(node->_dependents.size());
    node->unset_spawned();
  // At this point, the node storage might be destructed.
  for(size_t i=0; i<num_successors; ++i) {
    if(--(node->_successors[i]->_num_dependents) == 0) {
      taskflow->_schedule(*(node->_successors[i]));
  // A node without any successor should check the termination of topology
  if(num_successors == 0) {
    if(--(node->_topology->_num_sinks) == 0) {
      // This is the last executing node 
      bool is_framework = node->_topology->_handle.index() == 1;
      if(node->_topology->_work != nullptr) {
        std::invoke(node->_topology->_work);
      if(!is_framework) {
        node->_topology->_promise.set_value();
// ============================================================================
// BasicTaskflow Method Definitions
// ============================================================================
// Constructor
template <template <typename...> typename E>
BasicTaskflow<E>::BasicTaskflow() : 
  FlowBuilder {_graph},
  _executor {std::make_shared<Executor>(std::thread::hardware_concurrency())} {
// Constructor
template <template <typename...> typename E>
BasicTaskflow<E>::BasicTaskflow(unsigned N) : 
  FlowBuilder {_graph},
  _executor {std::make_shared<Executor>(N)} {
// Constructor
template <template <typename...> typename E>
BasicTaskflow<E>::BasicTaskflow(std::shared_ptr<Executor> e) :
  FlowBuilder {_graph},
  _executor {std::move(e)} {
  if(_executor == nullptr) {
    TF_THROW(Error::EXECUTOR, 
      "failed to construct taskflow (executor cannot be null)"
// Destructor
template <template <typename...> typename E>
BasicTaskflow<E>::~BasicTaskflow() {
  wait_for_topologies();
// Function: num_nodes
template <template <typename...> typename E>
size_t BasicTaskflow<E>::num_nodes() const {
  return _graph.size();
// Function: num_workers
template <template <typename...> typename E>
size_t BasicTaskflow<E>::num_workers() const {
  return _executor->num_workers();
// Function: num_topologies
template <template <typename...> typename E>
size_t BasicTaskflow<E>::num_topologies() const {
  return _topologies.size();
// Function: share_executor
template <template <typename...> typename E>
std::shared_ptr<typename BasicTaskflow<E>::Executor> BasicTaskflow<E>::share_executor() {
  return _executor;
// Procedure: dispatch 
template <template <typename...> typename E>
std::shared_future<void> BasicTaskflow<E>::dispatch() {
  if(_graph.empty()) {
    return std::async(std::launch::deferred, [](){}).share();
  auto& topology = _topologies.emplace_back(std::move(_graph));
  _schedule(topology._sources);
  return topology._future;
// Procedure: dispatch with registered callback
template <template <typename...> typename E>
template <typename C>
std::shared_future<void> BasicTaskflow<E>::dispatch(C&& c) {
  if(_graph.empty()) {
    return std::async(std::launch::deferred, [](){}).share();
  auto& topology = _topologies.emplace_back(std::move(_graph), std::forward<C>(c));
  _schedule(topology._sources);
  return topology._future;
// Procedure: wait_for_all
template <template <typename...> typename E>
void BasicTaskflow<E>::wait_for_all() {
  if(!_graph.empty()) {
    dispatch();
  wait_for_topologies();
// Procedure: wait_for_topologies
template <template <typename...> typename E>
void BasicTaskflow<E>::wait_for_topologies() {
  for(auto& t: _topologies){
    t._future.get();
  _topologies.clear();
// Procedure: _schedule
// The main procedure to schedule a give task node.
// Each task node has two types of tasks - regular and subflow.
template <template <typename...> typename E>
void BasicTaskflow<E>::_schedule(Node& node) {
  if(node._module != nullptr && !node.is_spawned()) {
    _set_module_node(node);
  _executor->emplace(*this, node);
// Procedure: _schedule
// The main procedure to schedule a set of task nodes.
// Each task node has two types of tasks - regular and subflow.
template <template <typename...> typename E>
void BasicTaskflow<E>::_schedule(PassiveVector<Node*>& nodes) {
  std::vector<Closure> closures;
  closures.reserve(nodes.size());
  for(auto src : nodes) {
    if(src->_module != nullptr && !src->is_spawned()) {
      _set_module_node(*src);
    closures.emplace_back(*this, *src);
  _executor->batch(closures);
template <template <typename...> typename E>
void BasicTaskflow<E>::_set_module_node(Node& node) {
  node._work = [&node, this, tgt{PassiveVector<Node*>()}] () mutable {
    // second time to enter this context
    if(node.is_spawned()) {
      node._dependents.resize(node._dependents.size()-tgt.size());
      for(auto& t: tgt) {
        t->_successors.clear();
      return ;
    // first time to enter this context
    node.set_spawned();
    PassiveVector<Node*> src;
    for(auto &n: node._module->_graph) {
      n._topology = node._topology;
      if(n.num_dependents() == 0) {
        src.push_back(&n);
      if(n.num_successors() == 0) {
        n.precede(node);
        tgt.push_back(&n);
    _schedule(src);
// Function: dump_topologies
template <template <typename...> typename E>
std::string BasicTaskflow<E>::dump_topologies() const {
  std::ostringstream os;
  for(const auto& tpg : _topologies) {
    tpg.dump(os);
  return os.str();
// Function: dump_topologies
template <template <typename...> typename E>
void BasicTaskflow<E>::dump_topologies(std::ostream& os) const {
  for(const auto& tpg : _topologies) {
    tpg.dump(os);
// Function: dump
template <template <typename...> typename E>
void BasicTaskflow<E>::dump(std::ostream& os) const {
  os << "digraph Taskflow {\n";
  for(const auto& node : _graph) {
    node.dump(os);
  os << "}\n";
// Function: dump
// Dumps the taskflow in graphviz. 
// The result can be viewed at http://www.webgraphviz.com/.
template <template <typename...> typename E>
std::string BasicTaskflow<E>::dump() const {
  std::ostringstream os;
  dump(os); 
  return os.str();
}  // end of namespace tf ----------------------------------------------------
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