diff --git a/matrix/matrix_multiplication_recursion.py b/matrix/matrix_multiplication_recursion.py new file mode 100644 index 000000000000..287142480ce7 --- /dev/null +++ b/matrix/matrix_multiplication_recursion.py @@ -0,0 +1,180 @@ +# @Author : ojas-wani +# @File : matrix_multiplication_recursion.py +# @Date : 10/06/2023 + + +""" +Perform matrix multiplication using a recursive algorithm. +https://en.wikipedia.org/wiki/Matrix_multiplication +""" +# type Matrix = list[list[int]] # psf/black currenttly fails on this line +Matrix = list[list[int]] + +matrix_1_to_4 = [ + [1, 2], + [3, 4], +] + +matrix_5_to_8 = [ + [5, 6], + [7, 8], +] + +matrix_5_to_9_high = [ + [5, 6], + [7, 8], + [9], +] + +matrix_5_to_9_wide = [ + [5, 6], + [7, 8, 9], +] + +matrix_count_up = [ + [1, 2, 3, 4], + [5, 6, 7, 8], + [9, 10, 11, 12], + [13, 14, 15, 16], +] + +matrix_unordered = [ + [5, 8, 1, 2], + [6, 7, 3, 0], + [4, 5, 9, 1], + [2, 6, 10, 14], +] +matrices = ( + matrix_1_to_4, + matrix_5_to_8, + matrix_5_to_9_high, + matrix_5_to_9_wide, + matrix_count_up, + matrix_unordered, +) + + +def is_square(matrix: Matrix) -> bool: + """ + >>> is_square([]) + True + >>> is_square(matrix_1_to_4) + True + >>> is_square(matrix_5_to_9_high) + False + """ + len_matrix = len(matrix) + return all(len(row) == len_matrix for row in matrix) + + +def matrix_multiply(matrix_a: Matrix, matrix_b: Matrix) -> Matrix: + """ + >>> matrix_multiply(matrix_1_to_4, matrix_5_to_8) + [[19, 22], [43, 50]] + """ + return [ + [sum(a * b for a, b in zip(row, col)) for col in zip(*matrix_b)] + for row in matrix_a + ] + + +def matrix_multiply_recursive(matrix_a: Matrix, matrix_b: Matrix) -> Matrix: + """ + :param matrix_a: A square Matrix. + :param matrix_b: Another square Matrix with the same dimensions as matrix_a. + :return: Result of matrix_a * matrix_b. + :raises ValueError: If the matrices cannot be multiplied. + + >>> matrix_multiply_recursive([], []) + [] + >>> matrix_multiply_recursive(matrix_1_to_4, matrix_5_to_8) + [[19, 22], [43, 50]] + >>> matrix_multiply_recursive(matrix_count_up, matrix_unordered) + [[37, 61, 74, 61], [105, 165, 166, 129], [173, 269, 258, 197], [241, 373, 350, 265]] + >>> matrix_multiply_recursive(matrix_1_to_4, matrix_5_to_9_wide) + Traceback (most recent call last): + ... + ValueError: Invalid matrix dimensions + >>> matrix_multiply_recursive(matrix_1_to_4, matrix_5_to_9_high) + Traceback (most recent call last): + ... + ValueError: Invalid matrix dimensions + >>> matrix_multiply_recursive(matrix_1_to_4, matrix_count_up) + Traceback (most recent call last): + ... + ValueError: Invalid matrix dimensions + """ + if not matrix_a or not matrix_b: + return [] + if not all( + (len(matrix_a) == len(matrix_b), is_square(matrix_a), is_square(matrix_b)) + ): + raise ValueError("Invalid matrix dimensions") + + # Initialize the result matrix with zeros + result = [[0] * len(matrix_b[0]) for _ in range(len(matrix_a))] + + # Recursive multiplication of matrices + def multiply( + i_loop: int, + j_loop: int, + k_loop: int, + matrix_a: Matrix, + matrix_b: Matrix, + result: Matrix, + ) -> None: + """ + :param matrix_a: A square Matrix. + :param matrix_b: Another square Matrix with the same dimensions as matrix_a. + :param result: Result matrix + :param i: Index used for iteration during multiplication. + :param j: Index used for iteration during multiplication. + :param k: Index used for iteration during multiplication. + >>> 0 > 1 # Doctests in inner functions are never run + True + """ + if i_loop >= len(matrix_a): + return + if j_loop >= len(matrix_b[0]): + return multiply(i_loop + 1, 0, 0, matrix_a, matrix_b, result) + if k_loop >= len(matrix_b): + return multiply(i_loop, j_loop + 1, 0, matrix_a, matrix_b, result) + result[i_loop][j_loop] += matrix_a[i_loop][k_loop] * matrix_b[k_loop][j_loop] + return multiply(i_loop, j_loop, k_loop + 1, matrix_a, matrix_b, result) + + # Perform the recursive matrix multiplication + multiply(0, 0, 0, matrix_a, matrix_b, result) + return result + + +if __name__ == "__main__": + from doctest import testmod + + failure_count, test_count = testmod() + if not failure_count: + matrix_a = matrices[0] + for matrix_b in matrices[1:]: + print("Multiplying:") + for row in matrix_a: + print(row) + print("By:") + for row in matrix_b: + print(row) + print("Result:") + try: + result = matrix_multiply_recursive(matrix_a, matrix_b) + for row in result: + print(row) + assert result == matrix_multiply(matrix_a, matrix_b) + except ValueError as e: + print(f"{e!r}") + print() + matrix_a = matrix_b + + print("Benchmark:") + from functools import partial + from timeit import timeit + + mytimeit = partial(timeit, globals=globals(), number=100_000) + for func in ("matrix_multiply", "matrix_multiply_recursive"): + print(f"{func:>25}(): {mytimeit(f'{func}(matrix_count_up, matrix_unordered)')}")