PLinq

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.Concurrent;
using System.Threading.Tasks;
using System.Threading;
using System.Diagnostics;
namespace BCBlockingAccess
{
    class Program
    {
        static int[] arr = Enumerable.Range(100000000, 100000).ToArray();

        static void Main(string[] args)
        {
            //PLINQ 的主要用途是通过在多核计算机上以并行方式执行查询委托来加快 LINQ to Objects 查询的执行速度。
            //当源集合中的每个元素的处理独立进行，各个委托之间未涉及到共享状态时，PLINQ 的性能最佳。 
            //在下面的示例中，queryA 可能适合于 PLINQ（假定其 Select 函数涉及大量工作）。
            //queryB 可能不适合，原因是 Select 语句中没有足够的工作，并且并行化的开销将抵销大部分或全部加速。
            //var queryA = from num in numberList.AsParallel()
            //             select ExpensiveFunction(num); //good for PLINQ

            //var queryB = from num in numberList.AsParallel()
            //             where num % 2 > 0
            //             select num; //not as good for PLINQ



            Utils.Measure("ping",()=>{
                var mm = from a in arr.AsParallel() where a % 2 == 0 select a;//每个元素的处理独立进行
                Console.WriteLine(mm.Count());
            });

            Utils.Measure("PLinqFunc", () => 
            {
                var mm = from a in arr.AsParallel() select Add(a);
                Console.WriteLine("changdu"+mm.Count());
            });
            Utils.Measure("Sequential", () =>
            {
                bool[] results = new bool[arr.Length];
                for (int i = 0; i < arr.Length; i++)
                {
                    results[i] = Utils.IsPrime(arr[i]);
                }
            });

            Utils.Measure("LINQ", () =>
            {
                bool[] results = arr.
                    Select(x => Utils.IsPrime(x)).
                    ToArray();
            });

            Utils.Measure("PLINQ", () =>
            {
                bool[] results = arr.AsParallel().AsOrdered().
                    Select(x => Utils.IsPrime(x)).
                    ToArray();
            });

          
            Console.ReadKey();
        }
        public static int Add(int i)
        {
            if (i % 2 == 0)
            {
                return i;
            }
            else
            {
                return 0;
            }
        }
    }
    class Utils
    {
        public static void Measure(string name, Action func)
        {
            Stopwatch stopwatch = new Stopwatch();
            
            stopwatch.Start();
            func();
            stopwatch.Stop();
            Console.WriteLine("-------------------------");
            Console.WriteLine("      " + name);
            Console.WriteLine("      Time: " + stopwatch.ElapsedMilliseconds + " ms");
            Console.WriteLine("-------------------------");

        }

        public static bool IsPrime(long x)
        {
            if (x <= 2) return x == 2;
            if (x % 2 == 0) return false;

            long sqrtx = (long)Math.Ceiling(Math.Sqrt(x));
            for (long i = 3; i <= sqrtx; i++)
            {
                if (x % i == 0) return false;
            }
            return true;
        }
    }
}