MatrixParFor

using System;
using System.Globalization;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace Matrix
{
    class Program
    {
        static double[,] Mult(double[,] a, double[,] b)
        {
            int c = a.GetLength(0);
            double[,] ans = new double[c, c];

            Parallel.For(0, c, i =>
            {
                for (int j = 0; j < c; j++)
                {
                    for (int k = 0; k < c; k++)
                    {
                        ans[i, j] += a[i, k] * b[k, j];
                    }
                }
            }
            );
           return ans;
        }

        static void Main(string[] args)
        {
            Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en");
            var lines = File.ReadAllLines("matrix.csv");
            var matrix = new double[lines.Length, lines.Length];
            var i = 0;
            foreach (string line in lines)
            {
                string[] elements = line.Split(',');
                int j = 0;
                foreach (string str in elements)
                {
                    matrix[i, j] = Double.Parse(str, CultureInfo.InvariantCulture);
                    j++;
                }
                i++;
            }


            Console.WriteLine(matrix[0, 0]);

            matrix = Mult(matrix, matrix);


            var stringArr = new string[lines.Length];

            for (int j = 0; j < lines.Length; j++)
            {
                var matrValue = matrix[0, 0].ToString();
                for (int k = 1; k < lines.Length; k++)
                {
                    matrValue += "," + matrix[j, k];
                }

                stringArr[j] = matrValue;
            }

           File.WriteAllLines("colomn.csv", stringArr);




            Console.ReadKey();
        }
    }
}