// Copyright (C) 2008 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_THREAD_POOl_CPPh_
#define DLIB_THREAD_POOl_CPPh_
#include "thread_pool_extension.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
thread_pool_implementation::
thread_pool_implementation (
unsigned long num_threads
) :
task_done_signaler(m),
task_ready_signaler(m),
we_are_destructing(false)
{
tasks.resize(num_threads);
threads.resize(num_threads);
for (unsigned long i = 0; i < num_threads; ++i)
{
threads[i] = std::thread([&](){this->thread();});
}
}
// ----------------------------------------------------------------------------------------
void thread_pool_implementation::
shutdown_pool (
)
{
{
auto_mutex M(m);
// first wait for all pending tasks to finish
bool found_task = true;
while (found_task)
{
found_task = false;
for (unsigned long i = 0; i < tasks.size(); ++i)
{
// If task bucket i has a task that is currently supposed to be processed
if (tasks[i].is_empty() == false)
{
found_task = true;
break;
}
}
if (found_task)
task_done_signaler.wait();
}
// now tell the threads to kill themselves
we_are_destructing = true;
task_ready_signaler.broadcast();
}
// wait for all threads to terminate
for (auto& t : threads)
t.join();
threads.clear();
// Throw any unhandled exceptions. Since shutdown_pool() is only called in the
// destructor this will kill the program.
for (auto&& task : tasks)
task.propagate_exception();
}
// ----------------------------------------------------------------------------------------
thread_pool_implementation::
~thread_pool_implementation()
{
shutdown_pool();
}
// ----------------------------------------------------------------------------------------
unsigned long thread_pool_implementation::
num_threads_in_pool (
) const
{
auto_mutex M(m);
return tasks.size();
}
// ----------------------------------------------------------------------------------------
void thread_pool_implementation::
wait_for_task (
uint64 task_id
) const
{
auto_mutex M(m);
if (tasks.size() != 0)
{
const unsigned long idx = task_id_to_index(task_id);
while (tasks[idx].task_id == task_id)
task_done_signaler.wait();
for (auto&& task : tasks)
task.propagate_exception();
}
}
// ----------------------------------------------------------------------------------------
void thread_pool_implementation::
wait_for_all_tasks (
) const
{
const thread_id_type thread_id = get_thread_id();
auto_mutex M(m);
bool found_task = true;
while (found_task)
{
found_task = false;
for (unsigned long i = 0; i < tasks.size(); ++i)
{
// If task bucket i has a task that is currently supposed to be processed
// and it originated from the calling thread
if (tasks[i].is_empty() == false && tasks[i].thread_id == thread_id)
{
found_task = true;
break;
}
}
if (found_task)
task_done_signaler.wait();
}
// throw any exceptions generated by the tasks
for (auto&& task : tasks)
task.propagate_exception();
}
// ----------------------------------------------------------------------------------------
bool thread_pool_implementation::
is_worker_thread (
const thread_id_type id
) const
{
for (unsigned long i = 0; i < worker_thread_ids.size(); ++i)
{
if (worker_thread_ids[i] == id)
return true;
}
// if there aren't any threads in the pool then we consider all threads
// to be worker threads
if (tasks.size() == 0)
return true;
else
return false;
}
// ----------------------------------------------------------------------------------------
void thread_pool_implementation::
thread (
)
{
{
// save the id of this worker thread into worker_thread_ids
auto_mutex M(m);
thread_id_type id = get_thread_id();
worker_thread_ids.push_back(id);
}
task_state_type task;
while (we_are_destructing == false)
{
long idx = 0;
// wait for a task to do
{ auto_mutex M(m);
while ( (idx = find_ready_task()) == -1 && we_are_destructing == false)
task_ready_signaler.wait();
if (we_are_destructing)
break;
tasks[idx].is_being_processed = true;
task = tasks[idx];
}
std::exception_ptr eptr = nullptr;
try
{
// now do the task
if (task.bfp)
task.bfp();
else if (task.mfp0)
task.mfp0();
else if (task.mfp1)
task.mfp1(task.arg1);
else if (task.mfp2)
task.mfp2(task.arg1, task.arg2);
}
catch(...)
{
eptr = std::current_exception();
}
// Now let others know that we finished the task. We do this
// by clearing out the state of this task
{ auto_mutex M(m);
tasks[idx].is_being_processed = false;
tasks[idx].task_id = 0;
tasks[idx].bfp.clear();
tasks[idx].mfp0.clear();
tasks[idx].mfp1.clear();
tasks[idx].mfp2.clear();
tasks[idx].arg1 = 0;
tasks[idx].arg2 = 0;
tasks[idx].eptr = eptr;
task_done_signaler.broadcast();
}
}
}
// ----------------------------------------------------------------------------------------
long thread_pool_implementation::
find_empty_task_slot (
) const
{
for (auto&& task : tasks)
task.propagate_exception();
for (unsigned long i = 0; i < tasks.size(); ++i)
{
if (tasks[i].is_empty())
return i;
}
return -1;
}
// ----------------------------------------------------------------------------------------
long thread_pool_implementation::
find_ready_task (
) const
{
for (unsigned long i = 0; i < tasks.size(); ++i)
{
if (tasks[i].is_ready())
return i;
}
return -1;
}
// ----------------------------------------------------------------------------------------
uint64 thread_pool_implementation::
make_next_task_id (
long idx
)
{
uint64 id = tasks[idx].next_task_id * tasks.size() + idx;
tasks[idx].next_task_id += 1;
return id;
}
// ----------------------------------------------------------------------------------------
unsigned long thread_pool_implementation::
task_id_to_index (
uint64 id
) const
{
return static_cast<unsigned long>(id%tasks.size());
}
// ----------------------------------------------------------------------------------------
uint64 thread_pool_implementation::
add_task_internal (
const bfp_type& bfp,
shared_ptr<function_object_copy>& item
)
{
auto_mutex M(m);
const thread_id_type my_thread_id = get_thread_id();
// find a thread that isn't doing anything
long idx = find_empty_task_slot();
if (idx == -1 && is_worker_thread(my_thread_id))
{
// this function is being called from within a worker thread and there
// aren't any other worker threads free so just perform the task right
// here
M.unlock();
bfp();
// return a task id that is both non-zero and also one
// that is never normally returned. This way calls
// to wait_for_task() will never block given this id.
return 1;
}
// wait until there is a thread that isn't doing anything
while (idx == -1)
{
task_done_signaler.wait();
idx = find_empty_task_slot();
}
tasks[idx].thread_id = my_thread_id;
tasks[idx].task_id = make_next_task_id(idx);
tasks[idx].bfp = bfp;
tasks[idx].function_copy.swap(item);
task_ready_signaler.signal();
return tasks[idx].task_id;
}
// ----------------------------------------------------------------------------------------
bool thread_pool_implementation::
is_task_thread (
) const
{
auto_mutex M(m);
return is_worker_thread(get_thread_id());
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_THREAD_POOl_CPPh_