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ThreadPool.cpp
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Thu, Apr 10, 22:55

ThreadPool.cpp
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#include "ThreadPool.hpp"
#include <chrono>
#include <vector>
#include <utility> //std::pair
std::vector<std::pair<size_t,size_t>> ThreadPool::split_range(size_t from,
size_t to,
size_t n_thread)
{ // contains the [from, to) slices
std::vector<std::pair<size_t,size_t>> coordinate_list(n_thread) ;
size_t by = to / n_thread ;
size_t from_current = from, to_current = 0 ;
for(size_t n=0; n<n_thread; n++)
{ from_current = (to_current == 0) ? 0 : (to_current) ;
to_current = from_current + by ;
(to_current + by > to) ? (to_current = to) : 0 ;
coordinate_list[n] = std::pair<size_t,size_t>(from_current, to_current) ;
}
// if there is some remains, distribute it equally over last threads
size_t remain = to - to_current ;
if(remain)
{ size_t from_correction = 0 ;
size_t to_correction = 1 ;
for(size_t n=n_thread-remain; n<n_thread; n++, from_correction++, to_correction++)
{ coordinate_list[n].first += from_correction ;
coordinate_list[n].second += to_correction ;
}
}
return coordinate_list ;
}
ThreadPool::ThreadPool(size_t n_threads, bool debug)
: queue_task(),
queue_mutex(),
queue_open(true),
debug(debug)
{ assert(n_threads > 0) ;
this->threads = std::vector<std::thread>(n_threads) ;
for(size_t i=0; i<n_threads; i++)
{ this->threads[i] = std::thread(&ThreadPool::thread_routine, this) ; }
}
ThreadPool::~ThreadPool()
{}
size_t ThreadPool::getNThread() const
{ return this->threads.size() ; }
void ThreadPool::addJob(std::function<void()>&& task)
{ // only add a job in the queues if they are open
if(this->isQueueOpen())
{ this->lock_mutex_queue() ;
// this->debug_print(std::string("started adding job")) ;
this->queue_task.push(task) ;
// this->debug_print(std::string("ended adding job")) ;
this->unlock_mutex_queue() ;
}
std::this_thread::sleep_for(std::chrono::milliseconds(5)) ;
}
void ThreadPool::join()
{ // closes the queues, later call to addJob() will be effect
this->close_queue() ;
// joins the threads
for(auto& thr : this->threads)
{ if(thr.joinable())
{ this->debug_print(std::string("joined a thread")) ;
thr.join() ;
}
}
}
void ThreadPool::thread_routine()
{
this->debug_print(std::string("started")) ;
while(true)
{
// get a function and the arguments value from the queue
std::function<void()> task ;
bool has_task = false ;
bool is_queue_open = this->isQueueOpen() ;
std::pair<size_t,size_t> args ;
this->lock_mutex_queue() ;
bool is_queue_empty = this->queue_task.empty() ;
if(not is_queue_empty)
{ // this->debug_print(std::string("fetching from queue")) ;
task = this->queue_task.front() ;
this->queue_task.pop() ;
has_task = true ;
}
this->unlock_mutex_queue() ;
// runs the task
if(has_task)
{ this->debug_print(std::string("working")) ;
task() ;
}
// exit
else if(is_queue_empty and not is_queue_open)
{ break ; }
std::this_thread::sleep_for(std::chrono::milliseconds(10)) ;
}
this->debug_print(std::string("ended")) ;
}
void ThreadPool::lock_mutex_queue()
{ this->queue_mutex.lock() ;
// this->debug_print(std::string("locked mutex")) ;
}
void ThreadPool::unlock_mutex_queue()
{ this->queue_mutex.unlock() ;
// this->debug_print(std::string("unlocked mutex")) ;
}
void ThreadPool::open_queue()
{ this->queue_open = true ; }
void ThreadPool::close_queue()
{ this->queue_open = false ; }
bool ThreadPool::isQueueOpen()
{ return this->queue_open ; }
bool ThreadPool::isDebugOn() const
{ return this->debug ; }
void ThreadPool::debug_print(const std::string& msg, std::ostream& out) const
{ if(this->isDebugOn())
{ std::hash<std::thread::id> hasher ;
char message[1024] ;
sprintf(message, "Thread %zu : %s\n",
hasher(std::this_thread::get_id()), msg.c_str()) ;
out << message ;
}
}

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