觀察 Random API 的執行緒安全問題

random-thread-safe-issue.cs

using System;
using System.Linq;
using System.Threading.Tasks;
					
public class Program
{
    public static void Main()
    {		
        var rng = new Random(); 
        Parallel.For(0, 16, _ =>
        {
            var numbers = new int[10000];
            for (var i = 0; i < numbers.Length; i++)
            {
                numbers[i] = rng.Next();
            }

            int zeroCount = numbers.Count(y => y == 0);
            Console.WriteLine("隨機函數產生了 {0} 個零。", zeroCount);
        });
        // 提示：隨機函數不應該產生很多 0。
    }
}