# 30) [C#] 문법13 (thread)

[예제1]

using System;
using static System.Console;
using System.Linq;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApp1
{
    class Program
    {
        // 소수 판단 프로그램이다.
        public static bool IsPrime(long num)
        {
            if (num < 2) { return false; }
            if (num % 2 == 0 && num != 2)
            {
                return false;
            }
            for (int i = 2; i < num; i++)
            {
                if (num % i == 0)
                { return false; }
            }
            return true;
        }
        static void Main(string[] args)
        {
            for (int ct = 1; ct <= 16; ct++)
            {
                long from = 0;
                long to = 20000;
                int taskCount = ct * 2;
                Func<object, List<long>> FindPrimeFunc = (objRange) =>
                {
                    long[] range = (long[])objRange;
                    List<long> found = new List<long>();
                    for (long i = range[0]; i < range[1]; i++)
                    {
                        if (IsPrime(i))
                            found.Add(i);
                    }
                    return found;
                };
                Task<List<long>>[] tasks = new Task<List<long>>[taskCount];
                long currentFrom = from;
                long currentTo = to / tasks.Length;
                for (int i = 0; i < tasks.Length; i++)
                {
                    tasks[i] = new Task<List<long>>(
                        FindPrimeFunc,
                        new long[] { currentFrom, currentTo }
                        );
                    //WriteLine("{0} {1}", currentFrom, currentTo);
                    currentFrom = currentTo + 1;
                    if (i == tasks.Length - 2)
                        currentTo = to;
                    else
                        currentTo = currentTo + (to / tasks.Length);
                }
                // Ready Go !!!!
                //ReadLine(); // 블로킹
                //WriteLine("Start !!!");
                DateTime startTime = DateTime.Now;
                //{
                //WriteLine(startTime);
                foreach (Task<List<long>> task in tasks)
                    task.Start();
                List<long> total = new List<long>();
                foreach (Task<List<long>> task in tasks)
                {
                    task.Wait();
                    total.AddRange(task.Result.ToArray());
                }
                //}
                DateTime endTime = DateTime.Now;
                TimeSpan ellaped = endTime - startTime;
                WriteLine("{0} {1} {2}", ct, ellaped, total.Count);
                //WriteLine();
            }
        }
    }
}
/*            for (int i = 0; i < 20; i++)
            {
                WriteLine(i + " " + IsPrime(i));
            }*/