Question

This is matrix product which saves the answer in C, such that C=A*B. So why won’t the C values change?

It uses special way that it calculates each column, because we want to use this method in Parallel programming such that each column evaluated in a single thread. I have tested something like this in pascal before, but in C# every thing is wrong.

Note: This is for homework and there is no parallel in this code yet.

class Program
{
    private static int n = 2;
    static int[,] A = new int[n, n];
    static int[,] B = new int[n, n];
    static int[,] C = new int[n, n];
    private static void Main(string[] args)
    {
        A[0, 0] = 2; A[0, 1] = 3;
        A[1, 0] = 5; A[1, 1] = 1;

        B[0, 0] = 3; B[0, 1] = 0;
        B[1, 0] = 1; B[1, 1] = 0;

        C[0, 0] = 0; C[0, 1] = 0;
        C[1, 0] = 0; C[1, 1] = 0;

        //Calculation 
        for (int z = 0; z < n; z++)
        {
            ComputeColumn(z);
        }
        PrintAnswer(C);
        Console.ReadKey();
    }
    private static void ComputeColumn(int n)
    {
        for (int i = 0; i < n; i++)
        {
            for (int k = 0; k < n; k++)
            {
                C[i, n] += (A[i, k] * B[k, n]);
            }
        }
    }
    private static void PrintAnswer(int[,] what)
    {
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j < n; j++)
            {
                Console.Write(what[i, j] + " ");
            }
            Console.WriteLine();
        }
    }
}

Answer 1

Try renaming the multiple uses of n

private static int n = 2;
ComputeColumn(int n)

to something more meaningful like

private static int NumberOfColumns = 2;
ComputeColumn(int currentColumn)

I think this will bring the problem to light fairly quickly.