Parallel.For循环与普通的for循环的比较

一、Parallel.For循环优于For的情况

代码：

 #region Parallel.For
        public static void ParallelForTest()
        {
            //标准For
            var dt = DateTime.Now;
            var rand = new Random(DateTime.Now.Millisecond);
            for (int i = 0; i < 20; i++)
            {
                Thread.Sleep(rand.Next(100, 1000));
            }
            var standerTime = (DateTime.Now - dt).TotalMilliseconds;
            Console.WriteLine("標準的for循環，耗時{0}毫秒", standerTime);

            //並行For
            dt = DateTime.Now;
            Parallel.For(0, 20, i =>
            {
                Thread.Sleep(rand.Next(100, 1000));
            });
            var parallelTime = (DateTime.Now - dt).TotalMilliseconds;
            Console.WriteLine("并行的for循環，耗時{0}毫秒", parallelTime);
            Console.WriteLine();
            if (standerTime <= parallelTime)
            {
                Console.WriteLine("----------标准的for循環節省{0}毫秒----------", (parallelTime - standerTime));
            }
            else
            {
                Console.WriteLine("----------并行的for循環節省{0}毫秒----------", (standerTime - parallelTime));
            }
            Console.ReadKey();
        }

        #endregion

运行结果：

 

二、For循环优于Parallel.For的情况

代码：

  #region For
        public static void ForTest()
        {
            Stopwatch sw = new Stopwatch();
            sw.Start();
            Console.WriteLine("Parallel.For");
            ParallelLoopResult result =
            Parallel.For(0, 10000, i =>
            {
                //打印空
                Console.Write("");

            });
            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine("Parallel.For總共花費{0}ms.", ts2.TotalMilliseconds);

            //簡單的For循環
            Stopwatch sw_Eq = new Stopwatch();
            sw_Eq.Start();
            Console.WriteLine("For");
            for (int i = 0; i < 10000; i++)
            {
                //打印空
                Console.Write("");
            }
            sw_Eq.Stop();
            TimeSpan tssw_Eq = sw_Eq.Elapsed;
            Console.WriteLine("for總共花費{0}ms.", tssw_Eq.TotalMilliseconds);
            Console.ReadKey();
        }
        #endregion

运行结果：