C++ 11 多线程学习笔记1 --线程创建

绝地灬酷狼 2023-07-05 11:48 12阅读 0赞

[**https://www.bilibili.com/video/av39161756?p=1**][https_www.bilibili.com_video_av39161756_p_1]

**并发编程**

包括多进程编程和多线程编程

**进程之间相互通讯的方法**

文件
    管道
    消息队列

**多线程的优点**

线程启动速度快
    轻量级
    开销低

**多线程的缺点**

管理较难
    不能在分布式系统下运行

**运行环境**

VS2013  + 控制台应用程序

--------------------

**1.HelloWord**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    void helloworld()
    { 
    	cout << "hello world \n";
    }
    
    int main()
    { 
    
    	//开启一个线程 
    	thread t(helloworld);
    	cout << "hello world main thread\n";
    
    	t.join();//主线程会等待t结束运行
    
    	system("pause");
    	return 0;
    }

![在这里插入图片描述][20200214180231387.png]

--------------------

**2.使用detach，主线程将不等子线程运行完就结束**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    void helloworld()
    { 
    	cout << "hello world" << endl;
    }
    
    int main()
    { 
    
    	//开启一个线程 
    	thread t(helloworld);
    	t.detach();
    	return 0;
    }

![按照视频里面是不会][20200214181712744.png]

**会只输出一个h就结束了**

--------------------

**3.一个线程先使用了detach之后就不能join否则会报错。所以join之前先进行判断**

![在这里插入图片描述][20200214182124807.png]

--------------------

**4.异常处理**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    void helloworld()
    { 
    	cout << "hello world" << endl;
    }
    
    int main()
    { 
    
    	thread t(helloworld);
    	
    	
    	for (int i = 0; i < 10; i++) { 
    		cout << "this is main thread" << endl;
    	}
    	//如果上面的代码抛出异常，t在join之前就会被销毁，这个时候代码就报错了
    	t.join();
    	
    	return 0;
    }

**修改为**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    void helloworld()
    { 
    	cout << "hello world" << endl;
    }
    
    int main()
    { 
    
    	thread t(helloworld);
    	try { 
    	
    		for (int i = 0; i < 10; i++) { 
    			cout << "this is main thread" << endl;
    		}
    
    	}
    	catch (...) { 
    		t.join();
    		throw;
    	}
    	t.join();
    	
    	return 0;
    }

**不管主线程是否抛出异常，t都可以正常join**

--------------------

**5.通过类创建线程**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    void helloworld()
    { 
    	cout << "hello world" << endl;
    }
    
    class Fctor { 
    public:
    	void operator()() { 
    		for (int i = 0; i > -10; i--) { 
    			cout << "from t1: " << i << endl;
    		}
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	thread t1(fct);
    	
    	
    	for (int i = 0; i < 10; i++) { 
    		cout << "from main: " << i << endl;
    	}
    	//如果上面的代码抛出异常，t在join之前就会被销毁，这个时候代码就报错了
    	t1.join();
    	
    	return 0;
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3_size_16_color_FFFFFF_t_70]

--------------------

**6.通过仿函数创建**

#include <iostream>
    #include <thread>
    #include <future>
    using namespace std;
    
    class Fctor { 
    public:
    	void operator()() { 
    		for (int i = 0; i > -10; i--) { 
    			cout << "from t1: " << i << endl;
    		}
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	//thread t1(fct);
    	//也可以
    	thread t1((Fctor()));
    	
    	for (int i = 0; i < 10; i++) { 
    		cout << "from main: " << i << endl;
    	}
    	//如果上面的代码抛出异常，t在join之前就会被销毁，这个时候代码就报错了
    	t1.join();
    	
    	return 0;
    }

**7.添加参数进行构造**

#include <iostream>
    #include <thread>
    #include <future>
    #include <string>
    using namespace std;
    
    class Fctor { 
    public:
    	void operator()(std::string msg) { 
    		for (int i = 0; i > -10; i--) { 
    			cout << "from t1: " << msg << endl;
    		}
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	string s = "hello world";
    	thread t1((Fctor()),s);
    	
    	for (int i = 0; i < 10; i++) { 
    		cout << "from main: " << i << endl;
    	}
    	//如果上面的代码抛出异常，t在join之前就会被销毁，这个时候代码就报错了
    	t1.join();
    	
    	return 0;
    }

--------------------

**8.通过引用传递参数std::ref**

#include <iostream>
    #include <thread>
    #include <future>
    #include <string>
    using namespace std;
    
    class Fctor { 
    public:
    	void operator()(std::string& msg) { 
    		
    		cout << "from t1: " << msg << endl;
    		msg = "xiugai";
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	string s = "hello world";
    	thread t1((Fctor()),std::ref(s));
    	t1.join();
    	cout << "from main: " << s << endl;
    
    	return 0;
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3_size_16_color_FFFFFF_t_70 1]

--------------------

**9.不通过引用，（可能导致数据竞争），通过move创建**

#include <iostream>
    #include <thread>
    #include <future>
    #include <string>
    using namespace std;
    
    class Fctor { 
    public:
    	void operator()(std::string msg) { 
    		
    		cout << "from t1: " << msg << endl;
    		msg = "xiugai";
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	string s = "hello world";
    	
    	cout << this_thread::get_id() << endl;
    
    	thread t1((Fctor()),std::move(s));
    	thread t2 = std::move(t1);
    
    	t2.join();
    	cout << "from main: " << s << endl;
    	cout << "from main: " << t2.get_id()<< endl;
    
    	return 0;
    }

![在这里插入图片描述][20200214191239880.png]  
**move把s移走了**

--------------------

**10. hardware\_concurrency输出可以并发编程的线程数量**

#include <iostream>
    #include <thread>
    #include <future>
    #include <string>
    using namespace std;
    
    class Fctor { 
    public:
    	void operator()(std::string msg) { 
    		
    		cout << "from t1: " << msg << endl;
    		msg = "xiugai";
    	}
    
    };
    int main()
    { 
    	Fctor fct;
    	string s = "hello world";
    	
    	cout << this_thread::get_id() << endl;
    
    	thread t1((Fctor()),std::move(s));
    	t1.join();
    
    	cout<<std::thread::hardware_concurrency()<<endl;
    
    	return 0;
    }

![在这里插入图片描述][20200214191629322.png]

[https_www.bilibili.com_video_av39161756_p_1]: https://www.bilibili.com/video/av39161756?p=1
[20200214180231387.png]: https://img-blog.csdnimg.cn/20200214180231387.png
[20200214181712744.png]: https://img-blog.csdnimg.cn/20200214181712744.png
[20200214182124807.png]: https://img-blog.csdnimg.cn/20200214182124807.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200214183455222.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/2020021419051510.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0wxNTU4MTk4NzI3,size_16,color_FFFFFF,t_70
[20200214191239880.png]: https://img-blog.csdnimg.cn/20200214191239880.png
[20200214191629322.png]: https://img-blog.csdnimg.cn/20200214191629322.png