Task: Kronecker product





Java: package kronecker;


public class Product {
  
  public static int[][] product(final int[][] a, final int[][] b) {
    
    
    final int[][] c = new int[a.length*b.length][];
    
    
    for (int ix = 0; ix < c.length; ix++) {
      final int num_cols = a[0].length*b[0].length;
      c[ix] = new int[num_cols];
    }
    
    
    for (int ia = 0; ia < a.length; ia++) {
      for (int ja = 0; ja < a[ia].length; ja++) {
        
        for (int ib = 0; ib < b.length; ib++) {
          for (int jb = 0; jb < b[ib].length; jb++) {
             c[b.length*ia+ib][b[ib].length*ja+jb] = a[ia][ja] * b[ib][jb];
          }
        }
      }
    }

    
    return c;
  }

  
  public static void print_matrix(final int[][] m) {
    
    
    
    
    final String[][] sts = new String[m.length][];
    int max_length = 0;  
    for (int im = 0; im < m.length; im++) {
      sts[im] = new String[m[im].length];
      for (int jm = 0; jm < m[im].length; jm++) {
        final String st = String.valueOf(m[im][jm]);
        if (st.length() > max_length) {
          max_length = st.length();
        }
        sts[im][jm] = st;
      }
    }

    
    
    
    final String format = String.format("%%%ds", max_length);
    for (int im = 0; im < m.length; im++) {
      System.out.print("|");
      
      for (int jm = 0; jm < m[im].length - 1; jm++) {
        System.out.format(format, m[im][jm]);
        System.out.print(" ");
      }
      System.out.format(format, m[im][m[im].length - 1]);
      System.out.println("|");
    }
  }

  
  private static void test(final int[][] a, final int[][] b) {
    
    System.out.println("Testing Kronecker product");
    System.out.println("Size of matrix a: " + a.length + " by " + a[0].length);
    System.out.println("Matrix a:");
    print_matrix(a);
    System.out.println("Size of matrix b: " + b.length + " by " + b[0].length);
    System.out.println("Matrix b:");
    print_matrix(b);
    System.out.println("Calculating matrix c as Kronecker product");
    final int[][] c = product(a, b);
    System.out.println("Size of matrix c: " + c.length + " by " + c[0].length);
    System.out.println("Matrix c:");
    print_matrix(c);
  }

  
  private static void test1() {
    
    final int[][] a = new int[2][];  
    a[0] = new int[]{1, 2};
    a[1] = new int[]{3, 4};
    final int[][] b = new int[2][];  
    b[0] = new int[]{0, 5};
    b[1] = new int[]{6, 7};
    
    test(a, b);
  }

  
  private static void test2() {
    
    final int[][] a = new int[3][];  
    a[0] = new int[]{0, 1, 0};
    a[1] = new int[]{1, 1, 1};
    a[2] = new int[]{0, 1, 0};
    final int[][] b = new int[3][];  
    b[0] = new int[]{1, 1, 1, 1};
    b[1] = new int[]{1, 0, 0, 1};
    b[2] = new int[]{1, 1, 1, 1};
    
    test(a, b);
  }

  
  public static void main(final String[] args) {
    
    test1();
    test2();
  }

}



Python: 


a1 = [[1, 2], [3, 4]]
b1 = [[0, 5], [6, 7]]


a2 = [[0, 1, 0], [1, 1, 1], [0, 1, 0]]
b2 = [[1, 1, 1, 1], [1, 0, 0, 1], [1, 1, 1, 1]]

def kronecker(matrix1, matrix2):
    final_list = []
    sub_list = []

    count = len(matrix2)

    for elem1 in matrix1:
        counter = 0
        check = 0
        while check < count:
            for num1 in elem1:
                for num2 in matrix2[counter]:
                    sub_list.append(num1 * num2)
            counter += 1
            final_list.append(sub_list)
            sub_list = []
            check +=1
            
    return final_list


result1 = kronecker(a1, b1)
for elem in result1:
    print(elem)

print("")


result2 = kronecker(a2, b2)
for elem in result2:
    print(elem)