using System;

using System.Collections.Generic;

using System.Collections.Concurrent;

using System.Threading.Tasks;

using System.Diagnostics;

​

Console.WriteLine($"Running on a {Environment.GetEnvironmentVariable("PROCESSOR_IDENTIFIER")}");

var sw = Stopwatch.StartNew();

var primes = FindPrimesInRange(2, 250_001);

Console.WriteLine(string.Join(", ", primes));

Console.WriteLine($"Elapsed time: {sw.Elapsed}");

​

​

// Functions

static IEnumerable<int> FindPrimesInRange(int start, int end)

{

    var bag = new ConcurrentBag<int>();

    Parallel.For(start, end, i =>

    {

        if (IsPrime(i))

            bag.Add(i);

    });

​

    return bag;

}

​

static bool IsPrime(int n)

{

    var boundary = n / 2;

    for (var i = 2; i <= boundary; i++)

    {

        if (n % i == 0)

            return false;

    }

​

    return true;

}

​

​