update ParallelExample

DotNetGuidePractice/HelloDotNetGuide/Program.cs

@@ -13,6 +13,14 @@ namespace HelloDotNetGuide
         {
             Console.WriteLine("欢迎来到DotNetGuide练习空间！！！");
 
+            #region ParallelExample
+
+            //ParallelExample.ParallelForExample();
+            //ParallelExample.ParallelForEachExample();
+            //ParallelExample.ParallelForCounterexample();
+
+            #endregion
+
             #region ConstAndReadonlyExercise
 
             //ConstAndReadonlyExercise.UpdateApplicationNameValue();
@@ -54,7 +62,7 @@ namespace HelloDotNetGuide
             //LinqExercise.CountByExample();
             //LinqExercise.AggregateByExample();
             //LinqExercise.IndexExample();
-            LinqExercise.CommonMethodsInLINQ();
+            //LinqExercise.CommonMethodsInLINQ();
 
             #endregion
 

DotNetGuidePractice/HelloDotNetGuide/异步多线程编程/ParallelExample.cs

@@ -0,0 +1,105 @@
+using System.Diagnostics;
+
+namespace HelloDotNetGuide.异步多线程编程
+{
+    public class ParallelExample
+    {
+        public static void ParallelForExample()
+        {
+            var length = 1000000;
+            var stopwatch = Stopwatch.StartNew();
+
+            // 统计普通 for 循环耗时
+            for (int i = 0; i < length; i++)
+            {
+                for (int j = 0; j < 1000; j++)
+                {
+                    var sum = i * j;
+                }
+            }
+            stopwatch.Stop();
+            Console.WriteLine($"普通 for 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
+
+            stopwatch.Restart();
+
+            // 统计 Parallel.For 循环耗时
+            Parallel.For(0, length, i =>
+            {
+                for (int j = 0; j < 1000; j++)
+                {
+                    var sum = i * j;
+                }
+            });
+
+            stopwatch.Stop();
+            Console.WriteLine($"Parallel.For 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
+            Console.ReadKey();
+        }
+
+        public static void ParallelForEachExample()
+        {
+            var length = 1000000;
+            var numbers = Enumerable.Range(0, length).ToList();
+
+            var stopwatch = Stopwatch.StartNew();
+
+            // 统计普通 foreach 循环耗时
+            foreach (var i in numbers)
+            {
+                for (int j = 0; j < 1000; j++)
+                {
+                    var sum = i * j;
+                }
+            }
+            stopwatch.Stop();
+            Console.WriteLine($"普通 foreach 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
+
+            stopwatch.Restart();
+
+            // 统计 Parallel.ForEach 循环耗时
+            Parallel.ForEach(numbers, i =>
+            {
+                for (int j = 0; j < 1000; j++)
+                {
+                    var sum = i * j;
+                }
+            });
+
+            stopwatch.Stop();
+            Console.WriteLine($"Parallel.ForEach 循环耗时: {stopwatch.ElapsedMilliseconds} 毫秒");
+            Console.ReadKey();
+        }
+
+        public static void ParallelForCounterexample()
+        {
+            object lockObj = new object();
+
+            var stopwatch = Stopwatch.StartNew();
+            long sumFor = 0;
+            for (int i = 0; i < 1000; i++)
+            {
+                sumFor += i; // 简单累加
+            }
+            stopwatch.Stop();
+            Console.WriteLine($"普通 for 循环: 结果 = {sumFor}, 耗时 = {stopwatch.ElapsedMilliseconds} 毫秒");
+
+
+            stopwatch.Restart();
+
+            long sumParallel = 0;
+            Parallel.For(0, 1000, i =>
+            {
+                // 因为多个线程同时修改同一个变量会导致计算结果丢失，lock 能确保每次只有一个线程可以修改，保证结果正确。
+                lock (lockObj)
+                {
+                    sumParallel += i;
+                }
+            });
+
+            stopwatch.Stop();
+            Console.WriteLine($"Parallel.For: 结果 = {sumParallel}, 耗时 = {stopwatch.ElapsedMilliseconds} 毫秒");
+
+            Console.ReadKey();
+        }
+    }
+}