初学多线程（一）--保护共享资源

1.共享资源未被保护，被多个线程并行访问，会发生资源分配上的冲突，两种方法保护共享资源

ps:共享资源像静态类中的字段，方法

How to protect shared resources from concurrent access?

1.使用 Interlocked.Increment(字段)
//在System.Threading
class Program
{
static int total = 0;
static void Main(string[] args)
{
Stopwatch sp = Stopwatch.StartNew();
Thread t1 = new Thread(AddToMillion);
Thread t2 = new Thread(AddToMillion);
Thread t3 = new Thread(AddToMillion);
t1.Start();
t2.Start();
t3.Start();
t1.Join();
t2.Join();
t3.Join();
Console.WriteLine("the total = " + total .ToString ());
sp.Stop();
Console.WriteLine("ticks = "+sp.ElapsedTicks);
}
static void AddToMillion()
{
for (int i = 0; i < 1000000; i++)
{
Interlocked.Increment(total);
}
}
}
运行结果：the total = 30000
ticks = 117078

2.使用lock对code session 进行锁定
//使用lock时要创建一个私有的静态object对象
// private static object obj = new object();
class Program
{
static int total = 0;
static void Main(string[] args)
{
Stopwatch sp = Stopwatch.StartNew();
Thread t1 = new Thread(AddToMillion);
Thread t2 = new Thread(AddToMillion);
Thread t3 = new Thread(AddToMillion);
t1.Start();
t2.Start();
t3.Start();
t1.Join();
t2.Join();
t3.Join();
Console.WriteLine("the total = " + total .ToString ());
sp.Stop();
Console.WriteLine("ticks = "+ sp.ElapsedTicks);
}
static object obj = new object();
static void AddToMillion()
{
for (int i = 0; i < 1000000; i++)
{
lock(obj )
{
total++;
}
}
}
}
运行结果：total= 3000000
ticks = 334236

2.Interlocked类只能对int/long类型的字段addition/subtraction(increment , decrement ,add etc)，这个类包含自增自减的方法，所以Interlocked.Increment(total),中total不用写成total++