詳解C#如何使用屏障實現(xiàn)多線程并發(fā)操作保持同步

更新時間：2024年01月24日 09:04:09 作者：rjcql

這篇文章主要為大家詳細介紹了C#如何使用屏障實現(xiàn)多線程并發(fā)操作保持同步,文中的示例代碼簡潔易懂,具有一定的借鑒價值,有需要的小伙伴可以參考下

寫在前面

以下是微軟官方對屏障類的介紹，System.Threading.Barrier 可用來作為實現(xiàn)并發(fā)同步操作的基本單元，讓多個線程(參與者)分階段并行處理目標算法。在達到代碼中的屏障點之前，每個參與者將繼續(xù)執(zhí)行，屏障表示工作階段的末尾；單個參與者到達屏障后將被阻止，直至所有參與者都已達到同一障礙。所有參與者都已達到屏障后，你可以選擇調(diào)用階段后操作。此階段后操作可由單線程用于執(zhí)行操作，而所有其他線程仍被阻止。執(zhí)行此操作后，所有參與者將不受阻止，繼續(xù)執(zhí)行直到滿足退出條件。

下面的程序用于統(tǒng)計兩個線程使用隨機算法重新隨機選擇字詞，分別在同一階段查找一半解決方案時所需的迭代次數(shù)（或階段數(shù)）。在每個線程隨機選擇字詞后，屏障后階段操作會比較兩個結(jié)果，以確定整個句子是否按正確的字詞順序呈現(xiàn)。

關(guān)鍵代碼如下：

barrier.SignalAndWait()

設置了代碼屏障點，代碼運行到這里會等待所有參與的線程都執(zhí)行完之前的代碼。

代碼實現(xiàn)

//#define TRACE
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
namespace BarrierSimple
{
    class Program
    {
        static string[] words1 = new string[] { "brown", "jumps", "the", "fox", "quick" };
        static string[] words2 = new string[] { "dog", "lazy", "the", "over" };
        static string solution = "the quick brown fox jumps over the lazy dog.";
 
        static bool success = false;
        static Barrier barrier = new Barrier(2, (b) =>
        {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < words1.Length; i++)
            {
                sb.Append(words1[i]);
                sb.Append(" ");
            }
            for (int i = 0; i < words2.Length; i++)
            {
                sb.Append(words2[i]);
 
                if (i < words2.Length - 1)
                    sb.Append(" ");
            }
            sb.Append(".");
#if TRACE
            System.Diagnostics.Trace.WriteLine(sb.ToString());
#endif
            Console.CursorLeft = 0;
            Console.Write("Current phase: {0}", barrier.CurrentPhaseNumber);
            if (String.CompareOrdinal(solution, sb.ToString()) == 0)
            {
                success = true;
                Console.WriteLine("\r\nThe solution was found in {0} attempts", barrier.CurrentPhaseNumber);
            }
        });
 
        static void Main(string[] args)
        {
 
            Thread t1 = new Thread(() => Solve(words1));
            Thread t2 = new Thread(() => Solve(words2));
            t1.Start();
            t2.Start();
 
            // Keep the console window open.
            Console.ReadLine();
        }
 
        // Use Knuth-Fisher-Yates shuffle to randomly reorder each array.
        // For simplicity, we require that both wordArrays be solved in the same phase.
        // Success of right or left side only is not stored and does not count.
        static void Solve(string[] wordArray)
        {
            while (success == false)
            {
                Random random = new Random();
                for (int i = wordArray.Length - 1; i > 0; i--)
                {
                    int swapIndex = random.Next(i + 1);
                    string temp = wordArray[i];
                    wordArray[i] = wordArray[swapIndex];
                    wordArray[swapIndex] = temp;
                }
 
                // We need to stop here to examine results
                // of all thread activity. This is done in the post-phase
                // delegate that is defined in the Barrier constructor.
                barrier.SignalAndWait();
            }
        }
    }
}