Parallel Fibonacci Number Calculator

Question

I\'m using Task Parallel Library (TPL ) for calculating Fibonacci number. Program is given below:

        public static int Fib(int n)
        {
                     


        

Answer 1

Your program is very inneficient, because same calculation are repeated (Fib(n-1) actually recalculate the Fib number for all numbers < n -2, which has be done yet).

You should try this :

class Program
{
    static void Main(string[] args)
    {
        var sw = new Stopwatch();
        sw.Start();
        foreach (var nbr in Fibo().Take(5000))
        {
            Console.Write(nbr.ToString() + " ");
        }
        sw.Stop();
        Console.WriteLine();
        Console.WriteLine("Ellapsed : " + sw.Elapsed.ToString());
        Console.ReadLine();
    }

    static IEnumerable Fibo()
    {
        long a = 0;
        long b = 1;
        long t;

        while (true)
        {
            t = a + b;
            yield return t;
            a = b;
            b = t;
        }
    }
}

44th find in 5ms.

The slowest part of the code is the Console.Write in the loop.