Thread
没有参数的线程启动
Thread newThread = new Thread(new ThreadStart(DoWork)); newThread.Start();
有参数的线程启动
注意DoWork()的参数必须为object
Thread newThread2 = new Thread(new ParameterizedThreadStart(this.DoWork)); newThread2.Start("111");
AutoResetEvent
通知等待的其他线程，本线程已经工作做完.
比如要计算1-N的各个数的平方之和,每个数的平方由不同的线程去计算
/// <summary>
/// 求数组平方和
/// </summary>
public class GetSquareSum
{
//建立事件数组 ,N个线程,就N个AutoResetEvent
public AutoResetEvent[] autoEvents = null;
//数组
public int[] array = null;
public int Sum = 0;
public GetSquareSum(int []arrays)
{
this.array = arrays;
autoEvents = new AutoResetEvent[arrays.Length];
for (int i = 0; i < arrays.Length; i++)
{
autoEvents[i] = new AutoResetEvent(false);//初始化
}
this.GetResult();
WaitHandle.WaitAll(autoEvents);
//autoEvents.ToList().ForEach(s => s.WaitOne());
foreach (int r in array)
{
Sum += r;
}
Console.WriteLine("Sum="+Sum);
}
public void GetResult()
{
for (int i = 0; i < array.Length; i++)
{
Calculate(i);
}
}
/// <summary>
/// 计算第index个数
/// </summary>
/// <param name="index"></param>
public void Calculate(int index)
{
Thread newThread2 = new Thread(
new ParameterizedThreadStart(
(obj) =>
{
int j = (int)obj;
array[j] = array[j] * array[j];
Console.WriteLine(array[j]);
autoEvents[j].Set();
}
)
);
newThread2.Start(index);
}
}
ManualResetEvent
MSDN上的解释是：通知一个或多个正在等待的线程已发生事件。
例子解释：
- 打印方法已经准备好，但是打印的东西没准备好，所以打印之前mreInit.WaitOne(),等待资源
-
通过控制台输入资源,mreInit.Set()通知资源准备好,打印程序开始打印
public class ManualResetEventTestExample2 { private static ManualResetEvent mreInit; private string _test = ""; public void Test() { mreInit = new ManualResetEvent(false);// Thread newThread = new Thread(new ThreadStart(() => Print())); newThread.Start(); _test = (Console.ReadLine()); mreInit.Set(); } /// <summary> /// 打印程序准备就绪 /// </summary> private void Print() { mreInit.WaitOne(); Console.WriteLine(_test); } }
ManualResetEvent的reset看下面代码
public class ManualResetEventTestExample2
{
private static ManualResetEvent mreInit;
private string _test = "";
public void Test()
{
mreInit = new ManualResetEvent(false);//
new Thread(new ThreadStart(() => Print())).Start();//Print 1
_test = (Console.ReadLine());//Input 1
mreInit.Set();
mreInit.Reset();
new Thread(new ThreadStart(() => Print())).Start();//Print 2
new Thread(new ThreadStart(() => Print())).Start();//Print 3
new Thread(new ThreadStart(() => Print())).Start();//Print 4
new Thread(new ThreadStart(() => Print())).Start();//Print 5
_test = (Console.ReadLine());//Input 2
mreInit.Set();
}
/// <summary>
/// 打印程序准备就绪
/// </summary>
private void Print()
{
mreInit.WaitOne();
Console.WriteLine(_test);
}
print 1肯定会在输入后执行,Print 2,3,4,5的执行,则依赖reset.如果没有mreInit.Reset()这句,则Print1,2,3,4,5会直接依次执行.如果加了mreInit.Reset()这句,这Print2,3,4,5只有在input 2执行了之后才会执行.
Reset就是让ManualResetEvent回复到初始状态.
线程池 ThreadPool
public static bool QueueUserWorkItem (WaitCallback callBack); public static bool QueueUserWorkItem(WaitCallback callback, Object state);
这两个方法向线程池的队列添加一个工作项（work item）以及一个可选的状态数据。然后，这两个方法就会立即返回。
工作项其实就是由callback参数标识的一个方法，该方法将由线程池线程执行。 同时写的回调方法必须匹配System.Threading.WaitCallback委托类型，定义为：
public delegate void WaitCallback(Object state);
就是说如果要带参数，callback参数必须为object.
ThreadPool.QueueUserWorkItem(new WaitCallback(obj => { System.Threading.Thread.Sleep(1000); Console.WriteLine(obj.ToString()); }),"canshu");
或者这么写
ThreadPool.QueueUserWorkItem(new WaitCallback(Func), "canshu");
private void Func(object obj)
{
System.Threading.Thread.Sleep(1000);
Console.WriteLine(obj.ToString());
}
或者
ThreadPool.QueueUserWorkItem(a=>{Func(a);}, "canshu");
以下代码改造求平方的问题.
class ThreadPoolTest2
{
public void Test()
{ // List<int> result = new List<int>();
int sum = 0;
object lockobj = new object();
Action<object> action = obj =>
{
Parm p = (Parm)obj;
lock (lockobj)
{
sum += p.Num * p.Num;
}
p.Are.Set();
};
int[] array = new int[] { 1, 2, 3, 4, 5,6,7,8,9,10,11,12,13,14,15 };
AutoResetEvent[] autos = new AutoResetEvent[array.Length];
for (int i = 0; i < array.Length; i++)
{
autos[i] = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(a=>action(a), new Parm() { Are = autos[i], Num = array[i] });
}
Console.WriteLine(sum);
//WaitHandle.WaitAll(autos);
autos.ToList().ForEach(s=>s.WaitOne());
Console.WriteLine(sum);
}
class Parm
{
public int Num { set; get; }
public AutoResetEvent Are { set; get; }
}
}
注意:在sum += p.Num * p.Num这句必须lock,不然会得不到正确结果
CancellationTokenSource
例子讲解:有5个数组,需要在数组中找是否有0元素,找到则返回.
实现:每个数据开启一个现场,如果某一个线程先找到0,则返回,同时,通知其他线程不用计算了.
class CancellationTokenSourceTest2
{
public void Test()
{
CancellationTokenSource cts = new CancellationTokenSource();
CancellationToken token = cts.Token;
int[][] array = new int[][]
{
new []{1,2,3,0,5,6,7,8,9,10},
new []{1,2,3,4,5,6,7,8,9,0},
new []{1,2,3,4,5,6,7,8,0,10},
new []{1,2,3,4,5,6,0,8,9,10},
new []{1,2,3,4,5,0,7,8,9,10}
};
for (int i = 0; i < array.Length; i++)
{
Thread th = new Thread(new ParameterizedThreadStart
((obj) =>
{
Parm p = (Parm)obj;
int[] a = p.Value;
for (int n=0;n<a.Length;n++)
{
int j = a[n];
Console.WriteLine("in array " + p.Index +" "+ (n + 1) + " times");
if (!p.Cts.IsCancellationRequested)
{
if (j == 0)
{
p.Cts.Cancel();
Console.WriteLine("Cancelling at task " + p.Index + "th array");
break;
}
Thread.Sleep(1000);
}
else
{
break;
}
}
}
));
th.Start(new Parm() { Cts = cts, Value = array[i] , Index=i});
}
Console.ReadLine();//敲下回车后，，
}
public class Parm
{
public CancellationTokenSource Cts;
public int []Value;
public int Index;
}
}
运行结果,首先在第0个数组中找到,总共比较次数为20次左右.
也可以尝试用AutoResetEvent实现,用 WaitHandle.WaitAny()等待.
BeginInvoke 和 EndInvoke
例子1:说明异步执行,将一个数乘以2返回,异步后等待结果后求和.
class BeginInvokeTest
{
public void Test()
{
Func<int, int> GetDouble = (a) => { Console.WriteLine(a); return a * 2; };
IAsyncResult ar1 = GetDouble.BeginInvoke(100, null, null);
IAsyncResult ar2 = GetDouble.BeginInvoke(200, null, null);
int result = GetDouble.EndInvoke(ar1)+GetDouble.EndInvoke(ar2);
Console.WriteLine("result = " + result);
}
}
打印结果为
100
200
result = 600
或者
200
100
result = 600
100和200的打印是异步执行,不知道誰先执行完,但是求和得等到EndInvoke两个异步完成,才能计算
例子2:两个异步去发送消息,发送完成后,去做其他事情,并且在发送消息的回调中保存消息记录↓.
class BeginInvokeTest2//回调方法中处理
{
public void Test()
{
Func<string, string> SendMessage = (a) =>
{
System.Threading.Thread.Sleep(1000);
Console.WriteLine("发送消息:"+a+" ,");
return "OK";
};
AsyncCallback callback = (ar) =>
{
Parm p = (Parm)ar.AsyncState;
if (p.F.EndInvoke(ar) == "OK")
{
Console.WriteLine("消息发送成功,保存聊天记录 "+p.Message);
}
};
Parm p1=new Parm(){ F=SendMessage, Message= "message1"};
Parm p2 = new Parm() { F = SendMessage, Message = "message2" };
IAsyncResult iar1 = SendMessage.BeginInvoke(p1.Message, callback, p1);
IAsyncResult iar2 = SendMessage.BeginInvoke(p2.Message, callback, p2);
iar1.AsyncWaitHandle.WaitOne();//等待执行完毕,并不是等待callback执行完
iar2.AsyncWaitHandle.WaitOne();//等待执行完毕,并不是等待callback执行完
Console.WriteLine("消息发完,做其他事情");
Console.Read();
}
class Parm
{
public Func<string, string> F;
public string Message;
}
}
线程同步Interlocked.Increment
以原子操作的形式递增指定变量的值并存储结果
例子说明:用3种方法对初始值为1的进行一百次++操作.第一种直接加,第二,三种方法多线程.第三种用Interlocked.Increment.运行结果为第二种的结果值可能不为101.
class InterlockedTest
{
public void Test()
{
int N = 1;
for (int i = 1; i <= 100; i++)
{
N++;
}
Console.WriteLine(N);
int M = 1;
Action<object> action = obj =>
{
Parm p = (Parm)obj;
M++;
p.au.Set();
};
AutoResetEvent[] autos = new AutoResetEvent[100];
for (int i = 1; i <= 100; i++)
{
autos[i-1] = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(a=>action(a), new Parm() { au = autos[i-1], index = i });
}
autos.ToList().ForEach(s => s.WaitOne());
Console.WriteLine(M);
int Q = 1;
Action<object> action2 = obj =>
{
Parm p = (Parm)obj;
Interlocked.Increment(ref Q);
p.au.Set();
};
autos = new AutoResetEvent[100];
for (int i = 1; i <= 100; i++)
{
autos[i - 1] = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(a => action2(a), new Parm() { au = autos[i - 1], index = i });
}
autos.ToList().ForEach(s => s.WaitOne());
Console.WriteLine(Q);
}
public class Parm
{
public AutoResetEvent au;
public int index;
}
}
线程同步 Monitor.Enter和Lock
Lock关键字是一个语法糖，它将Monitor对象进行封装.
语法糖(Syntactic sugar),是由Peter J. Landin(和图灵一样的天才人物，是他最先发现了Lambda演算，由此而创立了函数式编程)创造的一个词语，它意指那些没有给计算机语言添加新功能，而只是对人类来说更“甜蜜”的语法。语法糖往往给程序员提供了更实用的编码方式，有益于更好的编码风格，更易读。不过其并没有给语言添加什么新东西。
例子同Interlocked.Increment,不再详细说明
class MonitorTest
{
public void Test()
{
int N = 1;
for (int i = 1; i <= 100; i++)
{
N++;
}
Console.WriteLine(N);
int M = 1;
Action<object> action = obj =>
{
Parm p = (Parm)obj;
M++;
p.au.Set();
};
AutoResetEvent[] autos = new AutoResetEvent[100];
for (int i = 1; i <= 100; i++)
{
autos[i - 1] = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(a => action(a), new Parm() { au = autos[i - 1], index = i });
}
autos.ToList().ForEach(s => s.WaitOne());
Console.WriteLine(M);
int Q = 1;
object objMonitor=new object();
Action<object> action2 = obj =>
{
Parm p = (Parm)obj;
Monitor.Enter(objMonitor);
try
{
Q++;
}
finally
{
Monitor.Exit(objMonitor);
}
p.au.Set();
};
autos = new AutoResetEvent[100];
for (int i = 1; i <= 100; i++)
{
autos[i - 1] = new AutoResetEvent(false);
ThreadPool.QueueUserWorkItem(a => action2(a), new Parm() { au = autos[i - 1], index = i });
}
autos.ToList().ForEach(s => s.WaitOne());
Console.WriteLine(Q);
}
public class Parm
{
public AutoResetEvent au;
public int index;
}
}
ReaderWriterLock
例子说明:ReaderWriterLockEntity有2个成员变量X,Y,读写方法各有2个,一个使用读写锁,一个直接读写.我们设定X和Y必须相等.
class ReaderWriterLockEntity
{
ReaderWriterLock locker = new ReaderWriterLock();
public int X { set; get; }
public int Y { set; get; }
public void ReadLock(ref int x, ref int y)
{
locker.AcquireReaderLock(Timeout.Infinite);
try
{
x = this.X;
y = this.Y;
}
finally
{
locker.ReleaseReaderLock();
}
}
public void WriteLock(int x, int y)
{
locker.AcquireWriterLock(Timeout.Infinite);
try
{
this.X = x;
Thread.Sleep(10);
this.Y = y;
}
finally
{
locker.ReleaseWriterLock();
}
}
public void Read(ref int x, ref int y)
{
x = this.X;
y = this.Y;
}
public void Write(int x, int y)
{
this.X = x;
Thread.Sleep(10);
this.Y = y;
}
}
读写类,其中Test方法中,开启两组现场写线程,对ReaderWriterLockEntity中的X,Y进行自增.两组读线程,不停的打印X,Y.
打印的结果中,有X和Y不相等的结果出现.
Test2方法中,加了读写锁,打印的结果,不会有X和Y不等的情况.
ReaderWriterLock和Lock的区别就是,当加了ReaderLock,应该不会影响多个ReaderLock的增加.一个资源可以被Reader Lock多次.而lock则达不到这个要求.所以,ReadWriterLock在某些场景,比Lock效率更高.
class ReaderWriterTest2
{
ReaderWriterLockEntity entity = new ReaderWriterLockEntity();
public void Test()
{
Action writer = () =>
{
int a = 10;
int b = 10;
//Console.WriteLine("************** Write *************");
for (int i = 0; i < 5; i++)
{
this.entity.Write(a++, b++);
Thread.Sleep(10);
}
};
Action reader = () =>
{
// Console.WriteLine("************** Reader *************");
int x=0, y=0;
for (int i = 0; i < 50; i++)
{
this.entity.Read(ref x, ref y);
Console.WriteLine("Read:X={0},y={1}", x, y);
Thread.Sleep(1);
}
};
//Writer Threads
Thread wt1 = new Thread(new ThreadStart(writer));
wt1.Start();
Thread wt2 = new Thread(new ThreadStart(writer));
wt2.Start();
//Reader Threads
Thread rt1 = new Thread(new ThreadStart(reader));
rt1.Start();
Thread rt2 = new Thread(new ThreadStart(reader));
rt2.Start();
}
public void Test2()
{
Action writer = () =>
{
int a = 10;
int b = 10;
for (int i = 0; i < 5; i++)
{
this.entity.WriteLock(a++, b++);
Thread.Sleep(10);
}
};
Action reader = () =>
{
int x = 0, y = 0;
for (int i = 0; i < 50; i++)
{
this.entity.ReadLock(ref x, ref y);
Console.WriteLine("Read:X={0},y={1}", x, y);
Thread.Sleep(1);
}
};
//Writer Threads
Thread wt1 = new Thread(new ThreadStart(writer));
wt1.Start();
Thread wt2 = new Thread(new ThreadStart(writer));
wt2.Start();
//Reader Threads
Thread rt1 = new Thread(new ThreadStart(reader));
rt1.Start();
Thread rt2 = new Thread(new ThreadStart(reader));
rt2.Start();
}
}
Semaphore信号量
例子说明:厕所有5个位置,每个人上厕所五秒.程序输入1后,表示有一个人要上厕所.如果厕所已满,则会自动等待.
class SemaphoreTest
{
Semaphore sem = new Semaphore(5,5);//厕所空的
public void In()
{
sem.WaitOne();
Console.WriteLine("有空位,上厕所");
Thread.Sleep(5000);//上厕所需要五秒
sem.Release();//上完了
Console.WriteLine("出厕所");
}
public void Out()
{
Thread.Sleep(5000);//上厕所需要五秒
sem.Release();
Console.WriteLine("出厕所");
}
public void Test()
{
while(true)
{
string input = Console.ReadLine();
if (input == "1")//入厕
{
new Thread(new ThreadStart(()=>{ In();})).Start(); ;
}
}
}
}
不同程序,不同的exe，只要信号量的Name相同，信号量是共享的。
例子说明:修改上厕所的程序.一个程序只负责入厕,什么时候出厕所,则由管理人员来控制(另一个程序). SemaphoreTest2运行后,输入5次1,表示有5个人入厕了.然后在输入几个1,表示还有人在等待.
class SemaphoreTest2
{
Semaphore sem = new Semaphore(0, 5, "AAA");//厕所空的
public void In()
{
sem.WaitOne();
Console.WriteLine("有空位,上厕所");
}
public void Test()
{
while (true)
{
string input = Console.ReadLine();
if (input == "1")//入厕
{
new Thread(new ThreadStart(() => { In(); })).Start(); ;
}
}
}
}
在启动另外的项目,代码如下:启动后,输入2(喊一个人出厕所),发现入厕程序会有人进入厕所
class SemaphoreTest3
{
Semaphore sem = new Semaphore(0,5,"AAA");//厕所空的
public void Out()
{
Thread.Sleep(1000);//上厕所需要五秒
sem.Release();
Console.WriteLine("出厕所");
}
public void Test()
{
while(true)
{
string input = Console.ReadLine();
if (input == "2")//出厕
{
new Thread(new ThreadStart(()=>{ Out();})).Start(); ;
}
}
}
}
注意:这是2个不同的程序,他们的Semaphore的Name是相同的.
有一点不明白的地方是在程序1中运行 Semaphore sem = new Semaphore(0, 5, "AAA");//表示厕所满了. 在运行第二个程序 Semaphore sem = new Semaphore(5, 5, "AAA");这时候,程序1中仍然是满的.在new的时候,没有互相干扰.
注意下面这个构造函数,可以检测信号量Name是否重复.
public Semaphore( int initialCount, int maximumCount, string name, out bool createdNew )
意外发现: Semaphore sem = new Semaphore(0, 5,"厕所"); 如果Name为中文,new Semaphore(0, 5,"厕所")和new Semaphore(5, 5,"厕所")是一样的.一开始就会有5个可用信号量.
Mutex
只理解了这句,Mutex本身是可以系统级别的，所以是可以跨越进程的。比如我们要实现一个软件不能同时打开两次，那么Mutex是可以实现的，而lock和monitor是无法实现的。其他和lock的区别,其实没太懂.