106 lines
3.1 KiB
C#
106 lines
3.1 KiB
C#
using System.Diagnostics;
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namespace HelloDotNetGuide.异步多线程编程
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{
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public class ParallelExample
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{
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public static void ParallelForExample()
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{
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var length = 1000000;
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var stopwatch = Stopwatch.StartNew();
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// 统计普通 for 循环耗时
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for (int i = 0; i < length; i++)
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{
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for (int j = 0; j < 1000; j++)
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{
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var sum = i * j;
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}
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}
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stopwatch.Stop();
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Console.WriteLine($"普通 for 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
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stopwatch.Restart();
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// 统计 Parallel.For 循环耗时
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Parallel.For(0, length, i =>
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{
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for (int j = 0; j < 1000; j++)
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{
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var sum = i * j;
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}
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});
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stopwatch.Stop();
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Console.WriteLine($"Parallel.For 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
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Console.ReadKey();
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}
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public static void ParallelForEachExample()
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{
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var length = 1000000;
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var numbers = Enumerable.Range(0, length).ToList();
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var stopwatch = Stopwatch.StartNew();
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// 统计普通 foreach 循环耗时
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foreach (var i in numbers)
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{
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for (int j = 0; j < 1000; j++)
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{
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var sum = i * j;
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}
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}
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stopwatch.Stop();
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Console.WriteLine($"普通 foreach 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
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stopwatch.Restart();
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// 统计 Parallel.ForEach 循环耗时
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Parallel.ForEach(numbers, i =>
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{
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for (int j = 0; j < 1000; j++)
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{
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var sum = i * j;
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}
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});
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stopwatch.Stop();
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Console.WriteLine($"Parallel.ForEach 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
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Console.ReadKey();
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}
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public static void ParallelForCounterexample()
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{
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object lockObj = new object();
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var stopwatch = Stopwatch.StartNew();
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long sumFor = 0;
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for (int i = 0; i < 1000; i++)
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{
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sumFor += i; // 简单累加
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}
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stopwatch.Stop();
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Console.WriteLine($"普通 for 循环: 结果 = {sumFor}, 耗时 = {stopwatch.ElapsedMilliseconds} 毫秒");
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stopwatch.Restart();
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long sumParallel = 0;
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Parallel.For(0, 1000, i =>
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{
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// 因为多个线程同时修改同一个变量会导致计算结果丢失，lock 能确保每次只有一个线程可以修改，保证结果正确。
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lock (lockObj)
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{
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sumParallel += i;
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}
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});
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stopwatch.Stop();
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Console.WriteLine($"Parallel.For: 结果 = {sumParallel}, 耗时 = {stopwatch.ElapsedMilliseconds} 毫秒");
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Console.ReadKey();
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}
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}
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}
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