opencv/modules/core/src/parallel_pthreads.cpp

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/*M///////////////////////////////////////////////////////////////////////////////////////
//
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// copy or use the software.
//
//
// License Agreement
// For Open Source Computer Vision Library
//
// Copyright (C) 2000-2008, Intel Corporation, all rights reserved.
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//
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#include "precomp.hpp"
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#ifdef HAVE_PTHREADS_PF
#include <algorithm>
#include <pthread.h>
namespace cv
{
class ThreadManager;
enum ForThreadState
{
eFTNotStarted = 0,
eFTStarted = 1,
eFTToStop = 2,
eFTStoped = 3
};
enum ThreadManagerPoolState
{
eTMNotInited = 0,
eTMFailedToInit = 1,
eTMInited = 2,
eTMSingleThreaded = 3
};
struct work_load
{
work_load()
{
clear();
}
work_load(const cv::Range& range, const cv::ParallelLoopBody& body, int nstripes)
{
set(range, body, nstripes);
}
void set(const cv::Range& range, const cv::ParallelLoopBody& body, unsigned int nstripes)
{
m_body = &body;
m_range = &range;
//ensure that nstripes not larger than range length
m_nstripes = std::min( unsigned(m_range->end - m_range->start) , nstripes);
m_block_size = ((m_range->end - m_range->start - 1)/m_nstripes) + 1;
//ensure that nstripes not larger than blocks count, so we would never go out of range
m_nstripes = std::min(m_nstripes, unsigned(((m_range->end - m_range->start - 1)/m_block_size) + 1) );
}
const cv::ParallelLoopBody* m_body;
const cv::Range* m_range;
unsigned int m_nstripes;
int m_block_size;
void clear()
{
m_body = 0;
m_range = 0;
m_nstripes = 0;
m_block_size = 0;
}
};
class ForThread
{
public:
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ForThread(): m_posix_thread(0), m_task_start(false), m_parent(0), m_state(eFTNotStarted), m_id(0)
{
}
//called from manager thread
bool init(size_t id, ThreadManager* parent);
//called from manager thread
void run();
//called from manager thread
void stop();
~ForThread();
private:
//called from worker thread
static void* thread_loop_wrapper(void* thread_object);
//called from worker thread
void execute();
//called from worker thread
void thread_body();
pthread_t m_posix_thread;
pthread_mutex_t m_thread_mutex;
pthread_cond_t m_cond_thread_task;
volatile bool m_task_start;
ThreadManager* m_parent;
volatile ForThreadState m_state;
size_t m_id;
};
class ThreadManager
{
public:
friend class ForThread;
static ThreadManager& instance()
{
CV_SINGLETON_LAZY_INIT_REF(ThreadManager, new ThreadManager())
}
static void stop()
{
ThreadManager& manager = instance();
if(manager.m_pool_state == eTMInited)
{
for(size_t i = 0; i < manager.m_num_threads; ++i)
{
manager.m_threads[i].stop();
}
}
manager.m_pool_state = eTMNotInited;
}
void run(const cv::Range& range, const cv::ParallelLoopBody& body, double nstripes);
size_t getNumOfThreads();
void setNumOfThreads(size_t n);
private:
ThreadManager();
~ThreadManager();
void wait_complete();
void notify_complete();
bool initPool();
size_t defaultNumberOfThreads();
std::vector<ForThread> m_threads;
size_t m_num_threads;
pthread_mutex_t m_manager_task_mutex;
pthread_cond_t m_cond_thread_task_complete;
bool m_task_complete;
unsigned int m_task_position;
unsigned int m_num_of_completed_tasks;
pthread_mutex_t m_manager_access_mutex;
static const char m_env_name[];
work_load m_work_load;
struct work_thread_t
{
work_thread_t(): value(false) { }
bool value;
};
cv::TLSData<work_thread_t> m_is_work_thread;
ThreadManagerPoolState m_pool_state;
};
const char ThreadManager::m_env_name[] = "OPENCV_FOR_THREADS_NUM";
ForThread::~ForThread()
{
if(m_state == eFTStarted)
{
stop();
pthread_mutex_destroy(&m_thread_mutex);
pthread_cond_destroy(&m_cond_thread_task);
}
}
bool ForThread::init(size_t id, ThreadManager* parent)
{
m_id = id;
m_parent = parent;
int res = 0;
res |= pthread_mutex_init(&m_thread_mutex, NULL);
res |= pthread_cond_init(&m_cond_thread_task, NULL);
if(!res)
{
res = pthread_create(&m_posix_thread, NULL, thread_loop_wrapper, (void*)this);
}
return res == 0;
}
void ForThread::stop()
{
if(m_state == eFTStarted)
{
pthread_mutex_lock(&m_thread_mutex);
m_state = eFTToStop;
pthread_mutex_unlock(&m_thread_mutex);
run();
pthread_join(m_posix_thread, NULL);
}
pthread_mutex_lock(&m_thread_mutex);
m_state = eFTStoped;
pthread_mutex_unlock(&m_thread_mutex);
}
void ForThread::run()
{
pthread_mutex_lock(&m_thread_mutex);
m_task_start = true;
pthread_cond_signal(&m_cond_thread_task);
pthread_mutex_unlock(&m_thread_mutex);
}
void* ForThread::thread_loop_wrapper(void* thread_object)
{
((ForThread*)thread_object)->thread_body();
return 0;
}
void ForThread::execute()
{
unsigned int m_current_pos = CV_XADD(&m_parent->m_task_position, 1);
work_load& load = m_parent->m_work_load;
while(m_current_pos < load.m_nstripes)
{
int start = load.m_range->start + m_current_pos*load.m_block_size;
int end = std::min(start + load.m_block_size, load.m_range->end);
load.m_body->operator()(cv::Range(start, end));
m_current_pos = CV_XADD(&m_parent->m_task_position, 1);
}
}
void ForThread::thread_body()
{
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(void)cv::utils::getThreadID(); // notify OpenCV about new thread
m_parent->m_is_work_thread.get()->value = true;
pthread_mutex_lock(&m_thread_mutex);
m_state = eFTStarted;
while(m_state == eFTStarted)
{
//to handle spurious wakeups
while( !m_task_start && m_state != eFTToStop )
pthread_cond_wait(&m_cond_thread_task, &m_thread_mutex);
if(m_state == eFTStarted)
{
execute();
m_task_start = false;
m_parent->notify_complete();
}
}
pthread_mutex_unlock(&m_thread_mutex);
}
ThreadManager::ThreadManager(): m_num_threads(0), m_task_complete(false), m_num_of_completed_tasks(0), m_pool_state(eTMNotInited)
{
int res = 0;
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
res |= pthread_mutex_init(&m_manager_access_mutex, &attr);
pthread_mutexattr_destroy(&attr);
res |= pthread_mutex_init(&m_manager_task_mutex, NULL);
res |= pthread_cond_init(&m_cond_thread_task_complete, NULL);
if(!res)
{
setNumOfThreads(defaultNumberOfThreads());
m_task_position = 0;
}
else
{
m_num_threads = 1;
m_pool_state = eTMFailedToInit;
m_task_position = 0;
//print error;
}
}
ThreadManager::~ThreadManager()
{
stop();
pthread_mutex_destroy(&m_manager_task_mutex);
pthread_cond_destroy(&m_cond_thread_task_complete);
pthread_mutex_destroy(&m_manager_access_mutex);
}
void ThreadManager::run(const cv::Range& range, const cv::ParallelLoopBody& body, double nstripes)
{
bool is_work_thread = m_is_work_thread.get()->value;
if( (getNumOfThreads() > 1) && !is_work_thread &&
(range.end - range.start > 1) && (nstripes <= 0 || nstripes >= 1.5) )
{
int res = pthread_mutex_trylock(&m_manager_access_mutex);
if(!res)
{
if(initPool())
{
if(nstripes < 1) nstripes = 4*m_threads.size();
double max_stripes = 4*m_threads.size();
nstripes = std::min(nstripes, max_stripes);
pthread_mutex_lock(&m_manager_task_mutex);
m_num_of_completed_tasks = 0;
m_task_position = 0;
m_task_complete = false;
m_work_load.set(range, body, cvCeil(nstripes));
for(size_t i = 0; i < m_threads.size(); ++i)
{
m_threads[i].run();
}
wait_complete();
}
else
{
//print error
body(range);
}
}
else
{
body(range);
}
}
else
{
body(range);
}
}
void ThreadManager::wait_complete()
{
//to handle spurious wakeups
while(!m_task_complete)
pthread_cond_wait(&m_cond_thread_task_complete, &m_manager_task_mutex);
pthread_mutex_unlock(&m_manager_task_mutex);
pthread_mutex_unlock(&m_manager_access_mutex);
}
void ThreadManager::notify_complete()
{
unsigned int comp = CV_XADD(&m_num_of_completed_tasks, 1);
if(comp == (m_num_threads - 1))
{
pthread_mutex_lock(&m_manager_task_mutex);
m_task_complete = true;
pthread_cond_signal(&m_cond_thread_task_complete);
pthread_mutex_unlock(&m_manager_task_mutex);
}
}
bool ThreadManager::initPool()
{
if(m_pool_state != eTMNotInited || m_num_threads == 1)
return true;
m_threads.resize(m_num_threads);
bool res = true;
for(size_t i = 0; i < m_threads.size(); ++i)
{
res |= m_threads[i].init(i, this);
}
if(res)
{
m_pool_state = eTMInited;
}
else
{
//TODO: join threads?
m_pool_state = eTMFailedToInit;
}
return res;
}
size_t ThreadManager::getNumOfThreads()
{
return m_num_threads;
}
void ThreadManager::setNumOfThreads(size_t n)
{
int res = pthread_mutex_lock(&m_manager_access_mutex);
if(!res)
{
if(n == 0)
{
n = defaultNumberOfThreads();
}
if(n != m_num_threads && m_pool_state != eTMFailedToInit)
{
if(m_pool_state == eTMInited)
{
stop();
m_threads.clear();
}
m_num_threads = n;
if(m_num_threads == 1)
{
m_pool_state = eTMSingleThreaded;
}
else
{
m_pool_state = eTMNotInited;
}
}
pthread_mutex_unlock(&m_manager_access_mutex);
}
}
size_t ThreadManager::defaultNumberOfThreads()
{
#ifdef __ANDROID__
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// many modern phones/tables have 4-core CPUs. Let's use no more
// than 2 threads by default not to overheat the devices
const unsigned int default_number_of_threads = 2;
#else
const unsigned int default_number_of_threads = (unsigned int)std::max(1, cv::getNumberOfCPUs());
#endif
unsigned int result = default_number_of_threads;
char * env = getenv(m_env_name);
if(env != NULL)
{
sscanf(env, "%u", &result);
result = std::max(1u, result);
//do we need upper limit of threads number?
}
return result;
}
void parallel_for_pthreads(const cv::Range& range, const cv::ParallelLoopBody& body, double nstripes);
size_t parallel_pthreads_get_threads_num();
void parallel_pthreads_set_threads_num(int num);
size_t parallel_pthreads_get_threads_num()
{
return ThreadManager::instance().getNumOfThreads();
}
void parallel_pthreads_set_threads_num(int num)
{
if(num < 0)
{
ThreadManager::instance().setNumOfThreads(0);
}
else
{
ThreadManager::instance().setNumOfThreads(size_t(num));
}
}
void parallel_for_pthreads(const cv::Range& range, const cv::ParallelLoopBody& body, double nstripes)
{
ThreadManager::instance().run(range, body, nstripes);
}
}
#endif