learning c++11 thread library

DavidingPlus · DavidingPlus · commit a9b3668d4686 · 2024-10-24T16:18:56.000+08:00
diff --git a/snippet/CppThreadLearning/AtomicTest/CMakeLists.txt b/snippet/CppThreadLearning/AtomicTest/CMakeLists.txt
@@ -0,0 +1 @@
+add_executable (AtomicTest main.cpp)
diff --git a/snippet/CppThreadLearning/AtomicTest/main.cpp b/snippet/CppThreadLearning/AtomicTest/main.cpp
@@ -0,0 +1,29 @@
+#include <iostream>
+#include <thread>
+#include <atomic>
+
+
+// 将临界资源定义为线程级别的原子操作的数据。
+// 即使是多线程，也要像同步进行一样同步操作 atomic 对象，从而省去了 mutex 上锁、解锁的时间消耗。故执行的更快。
+std::atomic<int> n = 0;
+
+
+void count()
+{
+    for (int i = 0; i < 10000; ++i) ++n;
+}
+
+
+int main()
+{
+    std::thread th[100];
+
+    for (auto &t : th) t = std::thread(count);
+
+    for (auto &t : th) t.join();
+
+    std::cout << n << std::endl;
+
+
+    return 0;
+}
diff --git a/snippet/CppThreadLearning/CMakeLists.txt b/snippet/CppThreadLearning/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_subdirectory (AtomicTest)
+add_subdirectory (MutexTest)
+add_subdirectory (ThreadTest)
diff --git a/snippet/CppThreadLearning/MutexTest/CMakeLists.txt b/snippet/CppThreadLearning/MutexTest/CMakeLists.txt
@@ -0,0 +1 @@
+add_executable (MutexTest main.cpp)
diff --git a/snippet/CppThreadLearning/MutexTest/main.cpp b/snippet/CppThreadLearning/MutexTest/main.cpp
@@ -0,0 +1,34 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+
+
+int n = 0;
+
+std::mutex mtx;
+
+
+void count()
+{
+    for (int i = 1; i <= 10000; i++)
+    {
+        mtx.lock();
+        n++;
+        mtx.unlock();
+    }
+}
+
+
+int main()
+{
+    std::thread th[100];
+
+    for (std::thread &t : th) t = std::thread(count);
+
+    for (std::thread &t : th) t.join();
+
+    std::cout << n << std::endl; // 加锁以后应该是 10000 * 100 == 1000000
+
+
+    return 0;
+}
diff --git a/snippet/CppThreadLearning/README.md b/snippet/CppThreadLearning/README.md
@@ -0,0 +1,8 @@
+# CppThreadLearning
+
+本目录用于学习 C++ 11 多线程的标准库。
+
+参考博客：[https://blog.csdn.net/sjc_0910/article/details/118861539](https://blog.csdn.net/sjc_0910/article/details/118861539)
+
+本目录的构建和其他目录类似，需要在本目录（CppThreadLearning，非含代码的子目录）中添加 .buildme 文件，其余流程相同。
+
diff --git a/snippet/CppThreadLearning/ThreadTest/CMakeLists.txt b/snippet/CppThreadLearning/ThreadTest/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_executable (ThreadTest1 main1.cpp)
+add_executable (ThreadTest2 main2.cpp)
+add_executable (ThreadTest3 main3.cpp)
diff --git a/snippet/CppThreadLearning/ThreadTest/main1.cpp b/snippet/CppThreadLearning/ThreadTest/main1.cpp
@@ -0,0 +1,22 @@
+#include <iostream>
+#include <thread>
+
+
+void doIt() { std::cout << "Hello, " << std::flush; }
+
+
+int main()
+{
+    // 线程是在 thread 对象被定义的时候开始执行的。而不是在调用 join() 时才执行的，调用 join() 只是阻塞等待线程结束并回收资源。
+    std::thread
+        a(doIt),
+        b([]()
+          { std::cout << "World!" << std::endl; });
+
+    // 没有执行 join() 或 detach() 的线程在程序结束时会引发异常。
+    a.join();
+    b.join();
+
+
+    return 0;
+}
diff --git a/snippet/CppThreadLearning/ThreadTest/main2.cpp b/snippet/CppThreadLearning/ThreadTest/main2.cpp
@@ -0,0 +1,27 @@
+#include <iostream>
+#include <thread>
+
+
+void countNumber(int id, int n)
+{
+    for (int i = 1; i <= n; ++i)
+        ;
+
+    std::cout << "Thread " << id << " finished!" << std::endl;
+}
+
+
+int main()
+{
+    constexpr int threadNum = 10;
+
+    std::thread th[threadNum];
+
+    for (int i = 0; i < threadNum; i++) th[i] = std::thread(countNumber, i, 100000000);
+
+    // thread 库中好像没有类似于 pthread_exit() 退出主线程并且不会影响其余线程的函数，这样就可以无脑 detach() 而不用考虑主线程执行完毕后结束进程的问题了。因此这里还是使用 join() 吧。
+    for (int i = 0; i < threadNum; i++) th[i].join();
+
+
+    return 0;
+}
diff --git a/snippet/CppThreadLearning/ThreadTest/main3.cpp b/snippet/CppThreadLearning/ThreadTest/main3.cpp
@@ -0,0 +1,32 @@
+#include <iostream>
+#include <thread>
+
+
+template <class T>
+void changevalue(T &x, T val) { x = val; }
+
+
+int main()
+{
+    constexpr int threadNum = 100;
+
+    std::thread th[threadNum];
+
+    int nums[threadNum];
+
+    // 回调函数的参数是一个左值引用，但是 std::thread 需要的是右值引用，因此直接传入编译器会报错
+    // std::ref 可以包装按引用传递的值；std::cref 可以包装按常量引用传递的值。这样就能把左值引用包装成右值引用
+    for (int i = 0; i < threadNum; i++) th[i] = std::thread(changevalue<int>, std::ref(nums[i]), i + 1);
+
+    for (int i = 0; i < threadNum; i++)
+    {
+        th[i].join();
+
+        std::cout << nums[i] << ' ';
+    }
+
+    std::cout << std::endl;
+
+
+    return 0;
+}
diff --git a/src/lthreadpool.cpp b/src/lthreadpool.cpp
@@ -2,7 +2,6 @@
  * @file lthreadpool.cpp
  * @author DavidingPlus (davidingplus@qq.com)
  * @brief 线程池类源文件。
- * @date 2024-10-21
  *
  * Copyright (c) 2024 电子科技大学 刘治学
  *
diff --git a/src/lthreadpool.h b/src/lthreadpool.h
@@ -2,7 +2,6 @@
  * @file lthreadpool.h
  * @author DavidingPlus (davidingplus@qq.com)
  * @brief 线程池类头文件。
- * @date 2024-10-21
  *
  * Copyright (c) 2024 电子科技大学 刘治学
  *
@@ -11,5 +10,12 @@
 #ifndef _LTHREADPOOL_H_
 #define _LTHREADPOOL_H_
 
+#include <thread>
+
+
+class LThreadPool
+{
+};
+
 
 #endif

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+add_subdirectory (AtomicTest)`
	`2`	`+add_subdirectory (MutexTest)`
	`3`	`+add_subdirectory (ThreadTest)`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+add_executable (ThreadTest1 main1.cpp)`
	`2`	`+add_executable (ThreadTest2 main2.cpp)`
	`3`	`+add_executable (ThreadTest3 main3.cpp)`