做公司网站棋牌,百度的广告推广需要多少费用,云南做企业网站多少钱,临沂最新消息目录
一#xff1a;Atomic#xff1a;
二#xff1a;Thread 1. 创建线程
2. 小心移动(std::move)线程 3. 如何创建带参数的线程
4. 线程参数是引用类型时#xff0c;要小心谨慎。 5. 获取线程ID
6. jthread
7. 如何在线程中使用中断 stop_token
三#xff1a;如何…目录
一Atomic
二Thread 1. 创建线程
2. 小心移动(std::move)线程 3. 如何创建带参数的线程
4. 线程参数是引用类型时要小心谨慎。 5. 获取线程ID
6. jthread
7. 如何在线程中使用中断 stop_token
三如何解决数据竞争
1.有问题的代码
2.使用互斥
3.预防死锁
4. 自动释放锁
5. 延迟锁
6. 共享锁
7. 线程安全的初始化
四线程局部存储
五线程通信
1.条件变量
2. 防止虚假唤醒
3. 防止唤醒丢失
4.信号量
5. std::latch
六任务 1. std::promise, std::future
2. 用std::promise, std::future进行线程同步
3. std::async
4. std::package_task 一Atomic
#include atomic
#include thread
#include iostreamusing namespace std;std::atomic_int x, y;
int r1, r2;
void writeX() {x.store(1);r1 y.load();
}
void writeY() {y.store(1);r2 x.load();
} int main() {for (int i 0; i 100; i){x 0;y 0;std::thread a(writeX);std::thread b(writeY);a.join();b.join();std::cout r1 r2 std::endl;}return 0;
}
//可能的输出有三种情况01, 10, 11
//01:先执行线程a, 再执行线程b
//10:先执行线程b再执行线程a
//11:执行线程a一半后调度到线程b然后再回来
二Thread 1. 创建线程
#include atomic
#include thread
#include iostreamusing namespace std;void helloFunction() {cout function endl;
}class HelloFunctionObject {
public:void operator()() const {cout function object endl;}
};int main()
{thread t1(helloFunction); // functionHelloFunctionObject helloFunctionObject;thread t2(helloFunctionObject); // function objectthread t3([] { cout lambda function std::endl; }); // lambda functiont1.join(); //需要用join否则可能会出现主线程退出时t1线程还没有执行完的情况引起异常t2.join();t3.join();return 0;
}2. 小心移动(std::move)线程
#include atomic
#include thread
#include iostreamusing namespace std;int main()
{std::thread t([] { cout lambda function; });std::thread t2;t2 std::move(t);std::thread t3([] { cout lambda function; });/*此处代码有问题当t2 已经获得线程t后它已经是callable和joinable再赋值t3会terminate*/ t2 std::move(t3); std::terminate
} 3. 如何创建带参数的线程
#include atomic
#include thread
#include iostreamusing namespace std;//如何在线程中传递参数
void printStringCopy(string s) { cout s; }
void printStringRef(const string s) { cout s; }int main()
{string s{ C };thread tPerCopy([] { cout s; }); // Cthread tPerCopy2(printStringCopy, s); // CtPerCopy.join();tPerCopy2.join();thread tPerReference([] { cout s; }); // Cthread tPerReference2(printStringRef, s); // CtPerReference.join();tPerReference2.join();
}
4. 线程参数是引用类型时要小心谨慎。
#include iostreamusing namespace std;using std::this_thread::sleep_for;
using std::this_thread::get_id;struct Sleeper {Sleeper(int i_) :i{ i_ } {};void operator() (int k) {for (unsigned int j 0; j 5; j) {sleep_for(std::chrono::milliseconds(100));i k;}std::cout get_id(); // undefined behaviour}
private:int i;
};int main()
{int valSleeper 1000;//valSleeper 作为引用类型传给线程如果主线程先退出t线程使用valSleeper会产生未定义行为 并且主线程和t线程共享varSleeper产生数据竞争std::thread t(Sleeper(valSleeper), 5); t.detach();std::cout valSleeper; // undefined behaviour
}5. 获取线程ID
using namespace std;
using std::this_thread::get_id;int main()
{std::cout std::thread::hardware_concurrency() std::endl; // 4std::thread t1([] { std::cout get_id() std::endl; }); // 139783038650112std::thread t2([] { std::cout get_id() std::endl; }); // 139783030257408std::cout t1.get_id() std::endl; // 139783038650112std::cout t2.get_id() std::endl; // 139783030257408t1.swap(t2);std::cout t1.get_id() std::endl; // 139783030257408std::cout t2.get_id() std::endl; // 139783038650112std::cout get_id() std::endl; // 140159896602432t1.join();t2.join();
}
6. jthread
#include atomic
#include thread
#include iostreamusing namespace std;
using std::this_thread::get_id;//jthread 自动join()的线程
int main()
{std::jthread thr{ [] { std::cout std::jthread \n; } }; // std::jthreadstd::cout thr.joinable(): thr.joinable() \n; // thr.joinable(): true
}
7. 如何在线程中使用中断 stop_token
#include atomic
#include thread
#include iostreamusing namespace std;
using std::this_thread::get_id;
using namespace::std::literals;//字面量比如0.2s, C20能识别这种写法std::jthread nonInterruptable([] { // (1) 创建非中断线程int counter{ 0 };
while (counter 10) {std::this_thread::sleep_for(0.2s);std::cerr nonInterruptable: counter std::endl;counter;
}});
std::jthread interruptable([](std::stop_token stoken) { // (2) 创建可中断线程int counter{ 0 };
while (counter 10) {std::this_thread::sleep_for(0.2s);if (stoken.stop_requested()) return; // (3) 检查线程是否被中断std::cerr interruptable: counter std::endl;counter;
}});int main()
{std::this_thread::sleep_for(1s);std::cerr Main thread interrupts both jthreads std::endl;nonInterruptable.request_stop(); // (4)//请求中断非中断线程不理会interruptable.request_stop();//请求中断中断线程会响应
}
三如何解决数据竞争
1.有问题的代码
#include atomic
#include thread
#include iostreamusing namespace std;struct Worker {Worker(string n) :name(n) {};void operator() () {for (int i 1; i 3; i) {this_thread::sleep_for(chrono::milliseconds(200));//流本身是线程安全的但是cout是共享变量它会独占流多个线程访问cout时会引起数据竞争 cout name : Work i endl;}}
private:string name;
};int main()
{thread herb thread(Worker(Herb));thread andrei thread(Worker( Andrei));thread scott thread(Worker( Scott));thread bjarne thread(Worker( Bjarne));herb.join();andrei.join();scott.join();bjarne.join();}
2.使用互斥
#include atomic
#include thread
#include iostream
#include mutexusing namespace std;std::mutex mutexCout;struct Worker {Worker(string n) :name(n) {};void operator() () {for (int i 1; i 3; i) {this_thread::sleep_for(chrono::milliseconds(200));mutexCout.lock();cout name : Work i endl;mutexCout.unlock();}}
private:string name;
};int main()
{thread herb thread(Worker(Herb));thread andrei thread(Worker(Andrei));thread scott thread(Worker(Scott));thread bjarne thread(Worker(Bjarne));herb.join();andrei.join();scott.join();bjarne.join();}
3.预防死锁
m.lock();
sharedVar getVar(); //如果此处抛出异常会导致m.unlock未调用锁不能被释放其他线程无法得到锁进而可能产生死锁
m.unlock()
#include iostream
#include mutexusing namespace std;struct CriticalData {std::mutex mut;
};
void deadLock(CriticalData a, CriticalData b) {a.mut.lock();std::cout get the first mutex\n;std::this_thread::sleep_for(std::chrono::milliseconds(1));b.mut.lock();std::cout get the second mutex\n;a.mut.unlock(), b.mut.unlock();
}int main()
{CriticalData c1;CriticalData c2;//t1, t2在拿到锁后都在等对方释放锁std::thread t1([] { deadLock(c1, c2); });std::thread t2([] { deadLock(c2, c1); });t1.join();t2.join();
}
4. 自动释放锁
#include atomic
#include thread
#include iostream
#include mutexusing namespace std;std::mutex mutexCout;
struct Worker {Worker(std::string n) :name(n) {};void operator() () {for (int i 1; i 3; i) {std::this_thread::sleep_for(std::chrono::milliseconds(200));std::lock_guardstd::mutex myLock(mutexCout);//自动释放锁std::cout name : Work i std::endl;}}
private:std::string name;
};int main()
{thread herb thread(Worker(Herb));thread andrei thread(Worker(Andrei));thread scott thread(Worker(Scott));thread bjarne thread(Worker(Bjarne));herb.join();andrei.join();scott.join();bjarne.join();
}
5. 延迟锁
#include atomic
#include thread
#include iostream
#include mutexusing namespace std;using namespace std;
struct CriticalData {mutex mut;
};
void deadLockResolved(CriticalData a, CriticalData b) {unique_lockmutexguard1(a.mut, defer_lock);cout this_thread::get_id() : get the first lock endl;this_thread::sleep_for(chrono::milliseconds(1));unique_lockmutexguard2(b.mut, defer_lock);cout this_thread::get_id() : get the second lock endl;cout this_thread::get_id() : atomic locking endl;lock(guard1, guard2);
}int main()
{CriticalData c1;CriticalData c2;thread t1([] { deadLockResolved(c1, c2); });thread t2([] { deadLockResolved(c2, c1); });t1.join();t2.join();
}
6. 共享锁
#include mutex
...
std::shared_timed_mutex sharedMutex;
std::unique_lockstd::shared_timed_mutex writerLock(sharedMutex);
std::shared_lockstd::shared_time_mutex readerLock(sharedMutex);
std::shared_lockstd::shared_time_mutex readerLock2(sharedMutex);
7. 线程安全的初始化
//常量表达式是线程安全的
struct MyDouble{
constexpr MyDouble(double v):val(v){};
constexpr double getValue(){ return val; }
private:
double val
};
constexpr MyDouble myDouble(10.5);
std::cout myDouble.getValue(); // 10.5
//块内静态变量
void blockScope(){
static int MySharedDataInt 2011;
}
//once_flag, call_once
#include mutex
...
using namespace std;
once_flag onceFlag;
void do_once(){
call_once(onceFlag, []{ cout Only once. endl; });
}
thread t1(do_once);
thread t2(do_once);
四线程局部存储 std::mutex coutMutex;
thread_local std::string s(hello from );
void addThreadLocal(std::string const s2){
s s2;
std::lock_guardstd::mutex guard(coutMutex);
std::cout s std::endl;
std::cout s: s std::endl;
std::cout std::endl;
}
std::thread t1(addThreadLocal, t1);
std::thread t2(addThreadLocal, t2);
std::thread t3(addThreadLocal, t3);
std::thread t4(addThreadLocal, t4);
五线程通信
1.条件变量
#include atomic
#include thread
#include iostream
#include mutex
#include condition_variableusing namespace std;std::mutex mutex_;
std::condition_variable condVar;
bool dataReady false;
void doTheWork() {std::cout Processing shared data. std::endl;
}
void waitingForWork() {std::cout Worker: Waiting for work. std::endl;std::unique_lockstd::mutex lck(mutex_);condVar.wait(lck, [] { return dataReady; });doTheWork();std::cout Work done. std::endl;
}
void setDataReady() {std::lock_guardstd::mutex lck(mutex_);dataReady true;std::cout Sender: Data is ready. std::endl;condVar.notify_one();
}int main()
{std::thread t1(waitingForWork);std::thread t2(setDataReady);t1.join();t2.join();
}
2. 防止虚假唤醒
//为了防止虚假唤醒在唤醒前应进行条件检查且发送方应将条件置为true。
//dataReady true; //发送方设置条件满足
//[] { return dataReady; } //接收方进行条件检查
3. 防止唤醒丢失
//如果发送方在接收方等待之前就发送了唤醒可能会导致唤醒丢失因此要做两件事
//1: 要先等待后发送唤醒
//2: 在接收方的等待函数中要检查是否满足条件 [] { return dataReady; };4.信号量
#include atomic
#include thread
#include iostream
#include mutex
#include condition_variable
#include semaphore
#include vectorusing namespace std;std::vectorint myVec;std::counting_semaphore1 prepareSignal(0); // (1)
void prepareWork() {myVec.insert(myVec.end(), { 0, 1, 0, 3 });std::cout Sender: Data prepared. \n;prepareSignal.release(); // (2)
}void completeWork() {std::cout Waiter: Waiting for data. \n;prepareSignal.acquire(); // (3)myVec[2] 2;std::cout Waiter: Complete the work. \n;for (auto i : myVec) std::cout i ;std::cout \n;
}int main()
{std::thread t1(prepareWork);std::thread t2(completeWork);t1.join();t2.join();
}
5. std::latch
#include atomic
#include thread
#include iostream
#include mutex
#include condition_variable
#include semaphore
#include vector
#include latchusing namespace std;std::mutex coutMutex;std::latch workDone(2);
std::latch goHome(1); // (5)
void synchronizedOut(const std::string s) {std::lock_guardstd::mutex lo(coutMutex);std::cout s;
}class Worker {
public:Worker(std::string n) : name(n) { };void operator() () {// notify the boss when work is donesynchronizedOut(name : Work done!\n);workDone.count_down(); // (3) 完成工作// waiting before going homegoHome.wait();//等待老板发命令让他们回家synchronizedOut(name : Good bye!\n);}
private:std::string name;
};int main()
{std::cout BOSS: START WORKING! \n;Worker herb( Herb); // (1) 工人1std::thread herbWork(herb); //工人1必须完成自己的工作Worker scott( Scott); // (2) 工人2std::thread scottWork(scott);//工人2必须完成自己的工作workDone.wait(); // (4) 完成工作后等待std::cout \n;goHome.count_down();//老板发命令回家std::cout BOSS: GO HOME! \n;herbWork.join();scottWork.join();
}
6. std::barrier
#include barrier
#include iostream
#include string
#include syncstream
#include thread
#include vectorint main()
{const auto workers { Anil, Busara, Carl };auto on_completion []() noexcept{// locking not needed herestatic auto phase ... done\nCleaning up...\n;std::cout phase;phase ... done\n;};std::barrier sync_point(std::ssize(workers), on_completion);auto work [](std::string name){std::string product name worked\n;std::osyncstream(std::cout) product; // ok, op call is atomicsync_point.arrive_and_wait();product name cleaned\n;std::osyncstream(std::cout) product;sync_point.arrive_and_wait();};std::cout Starting...\n;std::vectorstd::jthread threads;threads.reserve(std::size(workers));for (auto const worker : workers)threads.emplace_back(work, worker);
}六任务 1. std::promise, std::future
#include future
#include iostreamvoid product(std::promiseint intPromise, int a, int b) {intPromise.set_value(a * b);
}
int main()
{int a 20;int b 10;std::promiseint prodPromise;std::futureint prodResult prodPromise.get_future();std::jthread prodThread(product, std::move(prodPromise), a, b);std::cout 20*10 prodResult.get(); // 20*10 200
}
2. 用std::promise, std::future进行线程同步
#include future
#include iostreamvoid doTheWork() {std::cout Processing shared data. std::endl;
}
void waitingForWork(std::futurevoid fut) {std::cout Worker: Waiting for work. std::endl;fut.wait();doTheWork();std::cout Work done. std::endl;
}
void setDataReady(std::promisevoid prom) {std::cout Sender: Data is ready. std::endl;prom.set_value();
}int main()
{std::promisevoid sendReady;auto fut sendReady.get_future();std::jthread t1(waitingForWork, std::move(fut));std::jthread t2(setDataReady, std::move(sendReady));}
3. std::async
#include future
#include iostreamusing std::chrono::duration;
using std::chrono::system_clock;
using std::launch;int main()
{auto begin system_clock::now();auto asyncLazy std::async(launch::deferred, [] { return system_clock::now(); });auto asyncEager std::async(launch::async, [] { return system_clock::now(); });std::this_thread::sleep_for(std::chrono::seconds(1));auto lazyStart asyncLazy.get() - begin;auto eagerStart asyncEager.get() - begin;auto lazyDuration durationdouble(lazyStart).count();auto eagerDuration durationdouble(eagerStart).count();std::cout lazyDuration sec; // 1.00018 sec.std::cout eagerDuration sec; // 0.00015489 sec.
}
#include future
#include iostream
#include threadusing std::chrono::duration;
using std::chrono::system_clock;
using std::launch;int main()
{int res;std::thread t([] { res 2000 11; });t.join();std::cout res std::endl; // 2011auto fut std::async([] { return 2000 11; });//异步调用std::cout fut.get() std::endl; // 2011
}
4. std::package_task
#include future
#include iostream
#include queue
#include threadusing namespace std;
using std::chrono::duration;
using std::chrono::system_clock;
using std::launch;struct SumUp {int operator()(int beg, int end) {for (int i beg; i end; i) sum i;return sum;}
private:int beg;int end;int sum{ 0 };
};int main()
{SumUp sumUp1, sumUp2;packaged_taskint(int, int) sumTask1(sumUp1);//任务1packaged_taskint(int, int) sumTask2(sumUp2);//任务2futureint sum1 sumTask1.get_future(); //任务1的结果futureint sum2 sumTask2.get_future(); //任务2的结果deque packaged_taskint(int, int) allTasks; //存储所有的任务allTasks.push_back(move(sumTask1));//将任务1加入队列allTasks.push_back(move(sumTask2));//将任务2加入队列int begin{ 1 };int increment{ 5000 };int end begin increment;while (not allTasks.empty()) {packaged_taskint(int, int) myTask move(allTasks.front());//取出1个任务allTasks.pop_front();thread sumThread(move(myTask), begin, end);//执行这个任务begin end;end increment;sumThread.detach();}auto sum sum1.get() sum2.get();//查询任务的结果cout sum;}
文章转载自： http://www.morning.fbjqq.cn.gov.cn.fbjqq.cn http://www.morning.cbnjt.cn.gov.cn.cbnjt.cn http://www.morning.fkgqn.cn.gov.cn.fkgqn.cn http://www.morning.fllfz.cn.gov.cn.fllfz.cn http://www.morning.kdldx.cn.gov.cn.kdldx.cn http://www.morning.lksgz.cn.gov.cn.lksgz.cn http://www.morning.hpnhl.cn.gov.cn.hpnhl.cn http://www.morning.mzgq.cn.gov.cn.mzgq.cn http://www.morning.hxbps.cn.gov.cn.hxbps.cn http://www.morning.nhzxd.cn.gov.cn.nhzxd.cn http://www.morning.cgthq.cn.gov.cn.cgthq.cn http://www.morning.lgnrl.cn.gov.cn.lgnrl.cn http://www.morning.glwyn.cn.gov.cn.glwyn.cn http://www.morning.yqsr.cn.gov.cn.yqsr.cn http://www.morning.errnull.com.gov.cn.errnull.com http://www.morning.ctlzf.cn.gov.cn.ctlzf.cn http://www.morning.dmfdl.cn.gov.cn.dmfdl.cn http://www.morning.ttxnj.cn.gov.cn.ttxnj.cn http://www.morning.weitao0415.cn.gov.cn.weitao0415.cn http://www.morning.lxlzm.cn.gov.cn.lxlzm.cn http://www.morning.jltmb.cn.gov.cn.jltmb.cn http://www.morning.ltypx.cn.gov.cn.ltypx.cn http://www.morning.jlthz.cn.gov.cn.jlthz.cn http://www.morning.rykmf.cn.gov.cn.rykmf.cn http://www.morning.lxthr.cn.gov.cn.lxthr.cn http://www.morning.qytpt.cn.gov.cn.qytpt.cn http://www.morning.c7624.cn.gov.cn.c7624.cn http://www.morning.mlbn.cn.gov.cn.mlbn.cn http://www.morning.mrfr.cn.gov.cn.mrfr.cn http://www.morning.szoptic.com.gov.cn.szoptic.com http://www.morning.ntqlz.cn.gov.cn.ntqlz.cn http://www.morning.zttjs.cn.gov.cn.zttjs.cn http://www.morning.sgrwd.cn.gov.cn.sgrwd.cn http://www.morning.qgjgsds.com.cn.gov.cn.qgjgsds.com.cn http://www.morning.hqjtp.cn.gov.cn.hqjtp.cn http://www.morning.dwmtk.cn.gov.cn.dwmtk.cn http://www.morning.kybyf.cn.gov.cn.kybyf.cn http://www.morning.xjqrn.cn.gov.cn.xjqrn.cn http://www.morning.dbdmr.cn.gov.cn.dbdmr.cn http://www.morning.kflbf.cn.gov.cn.kflbf.cn http://www.morning.krjyq.cn.gov.cn.krjyq.cn http://www.morning.bfysg.cn.gov.cn.bfysg.cn http://www.morning.lxlfr.cn.gov.cn.lxlfr.cn http://www.morning.phjny.cn.gov.cn.phjny.cn http://www.morning.kndt.cn.gov.cn.kndt.cn http://www.morning.kjxgc.cn.gov.cn.kjxgc.cn http://www.morning.nrftd.cn.gov.cn.nrftd.cn http://www.morning.pangucheng.cn.gov.cn.pangucheng.cn http://www.morning.fslrx.cn.gov.cn.fslrx.cn http://www.morning.lmqfq.cn.gov.cn.lmqfq.cn http://www.morning.tkcct.cn.gov.cn.tkcct.cn http://www.morning.rppf.cn.gov.cn.rppf.cn http://www.morning.qnbzs.cn.gov.cn.qnbzs.cn http://www.morning.sxfmg.cn.gov.cn.sxfmg.cn http://www.morning.xjqkh.cn.gov.cn.xjqkh.cn http://www.morning.lhztj.cn.gov.cn.lhztj.cn http://www.morning.pigcamp.com.gov.cn.pigcamp.com http://www.morning.xdttq.cn.gov.cn.xdttq.cn http://www.morning.lsbjj.cn.gov.cn.lsbjj.cn http://www.morning.xywfz.cn.gov.cn.xywfz.cn http://www.morning.hrjrt.cn.gov.cn.hrjrt.cn http://www.morning.hlnrj.cn.gov.cn.hlnrj.cn http://www.morning.mxgpp.cn.gov.cn.mxgpp.cn http://www.morning.jgcyn.cn.gov.cn.jgcyn.cn http://www.morning.wjrq.cn.gov.cn.wjrq.cn http://www.morning.3jiax.cn.gov.cn.3jiax.cn http://www.morning.xjqhh.cn.gov.cn.xjqhh.cn http://www.morning.twdkt.cn.gov.cn.twdkt.cn http://www.morning.gtqws.cn.gov.cn.gtqws.cn http://www.morning.kkqgf.cn.gov.cn.kkqgf.cn http://www.morning.jxzfg.cn.gov.cn.jxzfg.cn http://www.morning.ryfq.cn.gov.cn.ryfq.cn http://www.morning.pgmyn.cn.gov.cn.pgmyn.cn http://www.morning.wnrcj.cn.gov.cn.wnrcj.cn http://www.morning.qbgff.cn.gov.cn.qbgff.cn http://www.morning.rsnn.cn.gov.cn.rsnn.cn http://www.morning.rbktw.cn.gov.cn.rbktw.cn http://www.morning.fqqcn.cn.gov.cn.fqqcn.cn http://www.morning.sjwiki.com.gov.cn.sjwiki.com http://www.morning.qzsmz.cn.gov.cn.qzsmz.cn
