FindFrog.cs

using System;
using System.Linq;

namespace CSharp
{
    class FindFrog
    {
        static void Main(string[] args)
        {
            long now = DateTimeOffset.Now.ToUnixTimeSeconds();

            ulong sum = Enumerable.Range(-100, 201).AsParallel().Select(mx =>
            {
                ulong totalSum = 0;
                for (int my = -100; my <= 100; my++)
                {
                    for (int dx = -100; dx <= 100; dx++)
                    {
                        for (int dy = -100; dy <= 100; dy++)
                        {
                            totalSum += pair(pair(z2n(mx), z2n(my)), pair(z2n(dx), z2n(dy)));
                        }
                    }
                }
                return totalSum;
            }).Aggregate((x, y) => x + y);

            Console.WriteLine("sec: {0}", DateTimeOffset.Now.ToUnixTimeSeconds() - now);
            Console.WriteLine("sum: {0}", sum);
            Console.WriteLine("avg: {0}", sum / 1632240801);

        }

        static void simple()
        {
            long now = DateTimeOffset.Now.ToUnixTimeSeconds();

            ulong sum = 0;
            for (int mx = -100; mx <= 100; mx++)
            {
                for (int my = -100; my <= 100; my++)
                {
                    for (int dx = -100; dx <= 100; dx++)
                    {
                        for (int dy = -100; dy <= 100; dy++)
                        {
                            sum += pair(pair(z2n(mx), z2n(my)), pair(z2n(dx), z2n(dy)));
                        }
                    }
                }
            }
            Console.WriteLine("sec: {0}", DateTimeOffset.Now.ToUnixTimeSeconds() - now);
            Console.WriteLine("sum: {0}", sum);
            Console.WriteLine("avg: {0}", sum / 1632240801);
        }

        static ulong pair(ulong a, ulong b)
        {
            return ((a + b) * (a + b + 1) >> 1) + a;
        }

        static ulong z2n(int z)
        {
            return (ulong)(z >= 0 ? z << 1 : -1 - (z << 1));
        }
    }
}