How can I multiply two matrices in C#?

Question

Like described in the title, is there some library in the Microsoft framework which allows to multiply two matrices or do I have to write my own method to do this? // I\'ve

Answer 1

There is nothing built into .NET. You will have to write the multiplication yourself or use some third party library. I've blogged about one way to achieve this comparing two different implementations : a standard naive algorithm and one using unsafe code.

Answer 2

Below is the method to multiply int[3,4] matrix with int[4,3] matrix, it has time complexity of O(n cube) or Cubic time

class Program { static void Main(string[] args) {

        MultiplyMatrix();
    }

    static void MultiplyMatrix()
    {
        int[,] metrix1 = new int[3,4] { { 1, 2,3,2 }, { 3, 4,5,6 }, { 5, 6,8,4 } };
        int[,] metrix2 = new int[4, 3] { { 2, 5, 3 }, { 4, 5, 1 }, { 8, 7, 9 }, { 3, 7, 2 } };
        int[,] metrixMultplied = new int[3, 3];

        for (int row = 0; row < 3; row++)
        {
            for (int col = 0; col < 3; col++)
            { 
                for(int i=0;i<4;i++)
                {
                    metrixMultplied[row, col] = metrixMultplied[row, col] + metrix1[row, i] * metrix2[i, col];

                }
                Console.Write(metrixMultplied[row, col] + ", ");                   
            }
            Console.WriteLine();
        }
        Console.ReadLine();
    }
}

Answer 3

There are no such built in libraries. Unless you are using XNA - it has a Matrix class, though it is limited and designed for 3D games.

There are many matrix libraries for .NET though.

Answer 4

Whilst there's no built in Maths framework to do this in .NET (could use XNA's Maths library), there is a Matrix in the System.Windows.Media namespace. The Matrix structure has a Multiply method which takes in another Matrix and outputs a Matrix.

Matrix matrix1 = new Matrix(5, 10, 15, 20, 25, 30);
Matrix matrix2 = new Matrix(2, 4, 6, 8, 10, 12);

// matrixResult is equal to (70,100,150,220,240,352) 
Matrix matrixResult = Matrix.Multiply(matrix1, matrix2);

// matrixResult2 is also
// equal to (70,100,150,220,240,352) 
Matrix matrixResult2 = matrix1 * matrix2;

This is mainly used for 2D transformation:

Represents a 3x3 affine transformation matrix used for transformations in 2-D space.

but if it suits your needs, then there's no need for any third party libraries.