MatrixMultiply.java

import java.util.Random;

public class MatrixMultiply {
    static int n = 4096;
    static double[][] A = new double[n][n];
    static double[][] B = new double[n][n];
    static double[][] C = new double[n][n];

    public static void main(String[] args) {
        Random random = new Random();

        for (int i = 0 ; i < n ; ++i) {
            for (int j = 0 ; j < n ; ++j) {
                A[i][j] = random.nextDouble();
                B[i][j] = random.nextDouble();
                C[i][j] = 0;
            }
        }

        long start = System.nanoTime();

        for (int i = 0 ; i < n ; ++i) {
            for (int j = 0 ; j < n ; ++j) {
                for (int k = 0 ; k < n ; ++k) {
                    C[i][j] = A[i][k] * B[k][j]; 
                }
            }
        }

        long stop = System.nanoTime();

        double timeDifference = (stop - start) * 1e-9;

        System.out.println(timeDifference + " seconds");
    }
}