taskflow/taskflow/core/async.hpp at master · taskflow/taskflow · GitHub

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#pragma once

#include "executor.hpp"

#include "runtime.hpp"

namespace tf {

// ----------------------------------------------------------------------------

// Async Helper Methods

// ----------------------------------------------------------------------------

// Procedure: _schedule_async_task

template <typename... ArgsT>

void Executor::_schedule_async_task(ArgsT&&... args) {

// caller is a worker of the executor

if(auto w = this_worker(); w) {

// We don't do per-worker cache as it can cause bugs in corun that are very difficult to

// track. For example, when a worker invokes an async task and then immediately enter corun,

// it becomes very difficult to get the task out of its cache correctly.

_schedule(*w, animate(std::forward<ArgsT>(args)...));

}

// caller is a freelance thread

else{

_schedule(animate(std::forward<ArgsT>(args)...));

}

// Procedure: _schedule_dependent_async_task

template <std::input_iterator I, typename... ArgsT>

AsyncTask Executor::_schedule_dependent_async_task(I first, I last, size_t num_predecessors, ArgsT&&... args) {

// We need to create an async-task first to acquire an ownership.

AsyncTask task(animate(std::forward<ArgsT>(args)...));

for(; first != last; first++) {

auto&& x = *first;

if constexpr (std::is_pointer_v<std::remove_reference_t<decltype(x)>>) {

_process_dependent_async(task._node, *x, num_predecessors);

} else {

_process_dependent_async(task._node, x, num_predecessors);

}

if(num_predecessors == 0) {

// caller is a worker of the executor

if(auto w = this_worker(); w) {

// We don't do per-worker cache as it can cause bugs in corun that are very difficult to

// track. For example, when a worker invokes an async task and then immediately enter corun,

// it becomes very difficult to get the task out of its cache correctly.

_schedule(*w, task._node);

}

// caller is a freelance thread

else {

_schedule(task._node);

}

return task;

}

// Procedure: _tear_down_async

inline void Executor::_tear_down_async(Worker& worker, Node* node, Node*& cache) {

-------------------------------------------------------------------------------------------------

node->_topology | node->_parent | secenario

-------------------------------------------------------------------------------------------------

nullptr | nullptr | exe.async();

-------------------------------------------------------------------------------------------------

nullptr | 0x123 | exe.async([](Runtime rt){ rt.async(); });

| | task_group.async([](){});

-------------------------------------------------------------------------------------------------

0x123 | nullptr | ?

-------------------------------------------------------------------------------------------------

0x123 | 0x123 | tf.emplace([](Runtime& rt){ rt.async(); });

-------------------------------------------------------------------------------------------------

// no parent context (e.g., from executor)

if(auto parent = node->_parent; parent == nullptr) {

_decrement_topology();

}

// has parent context (e.g., from runtime, from task group)

else {

auto state = parent->_nstate;

if(parent->_join_counter.fetch_sub(1, std::memory_order_acq_rel) == 1) {

// this async is spawned from a preempted parent, so we need to resume it

if(state & NSTATE::PREEMPTED) {

_update_cache(worker, cache, static_cast<Node*>(parent));

}

recycle(node);

}

// ----------------------------------------------------------------------------

// Async

// ----------------------------------------------------------------------------

// Function: async

template <typename F>

auto Executor::async(F&& f) {

return async(DefaultTaskParams{}, std::forward<F>(f));

}

// Function: async

template <TaskParamsLike P, typename F>

auto Executor::async(P&& params, F&& f) {

_increment_topology();

return _async(std::forward(params), std::forward<F>(f), nullptr, nullptr);

}

// Function: _async

template <TaskParamsLike P, typename F>

auto Executor::_async(P&& params, F&& f, Topology* tpg, NodeBase* parent) {

// async task with runtime: [] (tf::Runtime&) -> void {}

if constexpr (is_runtime_task_v<F>) {

std::promise<void> p;

auto fu{p.get_future()};

_schedule_async_task(

NSTATE::NONE, ESTATE::EXPLICITLY_ANCHORED, std::forward(params), tpg, parent, 0,

std::in_place_type_t<Node::Async>{},

[p=MoC{std::move(p)}, f=std::forward<F>(f)](Runtime& rt, bool reentered) mutable {

if(!reentered) {

f(rt);

}

else {

auto& eptr = rt._node->_exception_ptr;

eptr ? p.object.set_exception(eptr) : p.object.set_value();

}

);

return fu;

}

// async task with closure: [] () -> auto { return ... }

else if constexpr (std::is_invocable_v<F>){

using R = std::invoke_result_t<F>;

std::packaged_task<R()> p(std::forward<F>(f));

auto fu{p.get_future()};

_schedule_async_task(

NSTATE::NONE, ESTATE::NONE, std::forward(params), tpg, parent, 0,

std::in_place_type_t<Node::Async>{},

[p=make_moc(std::move(p))]() mutable { p.object(); }

);

return fu;

}

else {

static_assert(dependent_false_v<F>,

"invalid async target - must be one of the following types:\n\

(1) [] (tf::Runtime&) -> void {}\n\

(2) [] () -> auto { ... return ... }\n"

);

}

// ----------------------------------------------------------------------------

// Silent Async

// ----------------------------------------------------------------------------

// Function: silent_async

template <typename F>

void Executor::silent_async(F&& f) {

silent_async(DefaultTaskParams{}, std::forward<F>(f));

}

// Function: silent_async

template <TaskParamsLike P, typename F>

void Executor::silent_async(P&& params, F&& f) {

_increment_topology();

_silent_async(std::forward(params), std::forward<F>(f), nullptr, nullptr);

}

// Function: _silent_async

template <TaskParamsLike P, typename F>

void Executor::_silent_async(P&& params, F&& f, Topology* tpg, NodeBase* parent) {

// silent task

if constexpr (is_runtime_task_v<F> || is_static_task_v<F>) {

_schedule_async_task(

NSTATE::NONE, ESTATE::NONE, std::forward(params), tpg, parent, 0,

std::in_place_type_t<Node::Async>{}, std::forward<F>(f)

);

}

// invalid silent async target

else {

static_assert(dependent_false_v<F>,

"invalid silent_async target - must be one of the following types:\n\

(1) [] (tf::Runtime&) -> void {}\n\

(2) [] () -> void { ... }\n"

);

}

// ----------------------------------------------------------------------------

// Silent Dependent Async

// ----------------------------------------------------------------------------

// Function: silent_dependent_async

template <typename F, AsyncTaskHandleLike... Tasks>

tf::AsyncTask Executor::silent_dependent_async(F&& func, Tasks&&... tasks) {

return silent_dependent_async(

DefaultTaskParams{}, std::forward<F>(func), std::forward<Tasks>(tasks)...

);

}

// Function: silent_dependent_async

template <TaskParamsLike P, typename F, AsyncTaskHandleLike... Tasks>

tf::AsyncTask Executor::silent_dependent_async(

P&& params, F&& func, Tasks&&... tasks

){

std::array<AsyncTask*, sizeof...(Tasks)> array{ (&tasks)... };

return silent_dependent_async(

std::forward(params), std::forward<F>(func), array.begin(), array.end()

);

}

// Function: silent_dependent_async

template <typename F, std::input_iterator I>

tf::AsyncTask Executor::silent_dependent_async(F&& func, I first, I last) {

return silent_dependent_async(DefaultTaskParams{}, std::forward<F>(func), first, last);

}

// Function: silent_dependent_async

template <TaskParamsLike P, typename F, std::input_iterator I>

tf::AsyncTask Executor::silent_dependent_async(

P&& params, F&& func, I first, I last

) {

_increment_topology();

return _silent_dependent_async(

std::forward(params), std::forward<F>(func), first, last, nullptr, nullptr

);

}

// Function: _silent_dependent_async

template <TaskParamsLike P, typename F, std::input_iterator I>

auto Executor::_silent_dependent_async(

P&& params, F&& func, I first, I last, Topology* tpg, NodeBase* parent

) {

size_t num_predecessors = std::distance(first, last);

return _schedule_dependent_async_task(first, last, num_predecessors,

NSTATE::NONE, ESTATE::REFCOUNT_ONE, std::forward(params), tpg, parent, num_predecessors,

std::in_place_type_t<Node::DependentAsync>{}, std::forward<F>(func)

);

}

// ----------------------------------------------------------------------------

// Dependent Async

// ----------------------------------------------------------------------------

// Function: dependent_async

template <typename F, AsyncTaskHandleLike... Tasks>

auto Executor::dependent_async(F&& func, Tasks&&... tasks) {

return dependent_async(DefaultTaskParams{}, std::forward<F>(func), std::forward<Tasks>(tasks)...);

}

// Function: dependent_async

template <TaskParamsLike P, typename F, AsyncTaskHandleLike... Tasks>

auto Executor::dependent_async(P&& params, F&& func, Tasks&&... tasks) {

std::array<AsyncTask*, sizeof...(Tasks)> array{ (&tasks)... };

return dependent_async(

std::forward(params), std::forward<F>(func), array.begin(), array.end()

);

}

// Function: dependent_async

template <typename F, std::input_iterator I>

auto Executor::dependent_async(F&& func, I first, I last) {

return dependent_async(DefaultTaskParams{}, std::forward<F>(func), first, last);

}

// Function: dependent_async

template <TaskParamsLike P, typename F, std::input_iterator I>

auto Executor::dependent_async(P&& params, F&& func, I first, I last) {

_increment_topology();

return _dependent_async(std::forward(params), std::forward<F>(func), first, last, nullptr, nullptr);

}

// Function: _dependent_async

template <TaskParamsLike P, typename F, std::input_iterator I>

auto Executor::_dependent_async(P&& params, F&& func, I first, I last, Topology* tpg, NodeBase* parent) {

size_t num_predecessors = std::distance(first, last);

// async with runtime: [] (tf::Runtime&) -> void {}

if constexpr (is_runtime_task_v<F>) {

std::promise<void> p;

auto fu{p.get_future()};

return std::make_pair(_schedule_dependent_async_task(first, last, num_predecessors,

NSTATE::NONE, ESTATE::EXPLICITLY_ANCHORED | ESTATE::REFCOUNT_ONE, std::forward(params), tpg, parent, num_predecessors,

std::in_place_type_t<Node::DependentAsync>{},

[p=MoC{std::move(p)}, f=std::forward<F>(func)] (tf::Runtime& rt, bool reentered) mutable {

if(!reentered) {

f(rt);

}

else {

auto& eptr = rt._node->_exception_ptr;

eptr ? p.object.set_exception(eptr) : p.object.set_value();

}

), std::move(fu));

}

// async without runtime: [] () -> auto { return ... }

else if constexpr(std::is_invocable_v<F>) {

using R = std::invoke_result_t<F>;

std::packaged_task<R()> p(std::forward<F>(func));

auto fu{p.get_future()};

return std::make_pair(_schedule_dependent_async_task(first, last, num_predecessors,

NSTATE::NONE, ESTATE::REFCOUNT_ONE, std::forward(params), tpg, parent, num_predecessors,

std::in_place_type_t<Node::DependentAsync>{},

[p=make_moc(std::move(p))] () mutable { p.object(); }

), std::move(fu));

}

else {

static_assert(dependent_false_v<F>, "invalid async callable");

}

// ----------------------------------------------------------------------------

// Dependent Async Helper Functions

// ----------------------------------------------------------------------------

// Procedure: _process_dependent_async

inline void Executor::_process_dependent_async(

Node* node, tf::AsyncTask& task, size_t& num_predecessors

) {

// special case: the task is not associated with any dependent-async task

if(task.empty()) {

num_predecessors = node->_join_counter.fetch_sub(1, std::memory_order_acq_rel) - 1;

return;

}

auto& state = task._node->_estate;

auto target = state.load(std::memory_order_acquire);

while (!(target & ESTATE::FINISHED)) {

// can only go from unlock and unfinished to locked

target &= ~ESTATE::LOCKED;

if(state.compare_exchange_weak(target, target | ESTATE::LOCKED,

std::memory_order_acq_rel,

std::memory_order_acquire)) {

task._node->_edges.push_back(node);

state.fetch_and(~ESTATE::LOCKED, std::memory_order_release);

return;

}

num_predecessors = node->_join_counter.fetch_sub(1, std::memory_order_acq_rel) - 1;

}

// Procedure: _tear_down_dependent_async

inline void Executor::_tear_down_dependent_async(Worker& worker, Node* node, Node*& cache) {

auto target = node->_estate.load(std::memory_order_acquire);

while(true) {

// We can only go from unlocked and unfinished to finished.

// Only this function can set the state to FINISHED.

target &= ~ESTATE::LOCKED;

if(node->_estate.compare_exchange_weak(target, target | ESTATE::FINISHED,

std::memory_order_acq_rel,

std::memory_order_acquire)) {

break;

}

// spawn successors whenever their dependencies are resolved

for(size_t i=0; i<node->_edges.size(); ++i) {

if(auto s = node->_edges[i];

s->_join_counter.fetch_sub(1, std::memory_order_acq_rel) == 1

) {

_update_cache(worker, cache, s);

}

-------------------------------------------------------------------------------------------------

node->_topology | node->_parent | secenario

-------------------------------------------------------------------------------------------------

nullptr | nullptr | exe.async();

-------------------------------------------------------------------------------------------------

nullptr | 0x123 | exe.async([](Runtime rt){ rt.async(); });

| | task_group.async([](){});

-------------------------------------------------------------------------------------------------

0x123 | nullptr | ?

-------------------------------------------------------------------------------------------------

0x123 | 0x123 | tf.emplace([](Runtime& rt){ rt.async(); });

-------------------------------------------------------------------------------------------------

// no parent context (e.g., from executor)

if(auto parent = node->_parent; parent == nullptr) {

_decrement_topology();

}

// has parent context (e.g., from runtime, from task group)

else {

auto state = parent->_nstate;

if(parent->_join_counter.fetch_sub(1, std::memory_order_acq_rel) == 1) {

// this async is spawned from a preempted parent, so we need to resume it

if(state & NSTATE::PREEMPTED) {

_update_cache(worker, cache, static_cast<Node*>(parent));

}

// now the executor no longer needs to retain ownership —

// decrement the refcount packed in the lower 24 bits of _estate.

// if it reaches zero, no AsyncTask handle remains and we can recycle.

if((node->_estate.fetch_sub(ESTATE::REFCOUNT_ONE, std::memory_order_acq_rel)

& ESTATE::REFCOUNT_MASK) == ESTATE::REFCOUNT_ONE) {

recycle(node);

}

} // end of namespace tf -----------------------------------------------------

taskflow/taskflow/core/async.hpp at master · taskflow/taskflow · GitHub

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