feat: Implemented Matrix Exponentiation Method (#11747)

* feat: add Matrix Exponentiation method
docs: updated the header documentation and added new documentation for
the new function.

* feat: added new function matrix exponetiation method

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* feat: This function uses the tail-recursive form of the Euclidean algorithm to calculate

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* reduced the number of characters per line in the comments

* removed unwanted code

* feat: Implemented a new function to swaap numbers without dummy variable

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* removed previos code

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* Update maths/fibonacci.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
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ARNAV RAJ 2024-10-04 21:59:39 +05:30 committed by GitHub
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@ -7,6 +7,8 @@ the Binet's formula function because the Binet formula function uses floats
NOTE 2: the Binet's formula function is much more limited in the size of inputs NOTE 2: the Binet's formula function is much more limited in the size of inputs
that it can handle due to the size limitations of Python floats that it can handle due to the size limitations of Python floats
NOTE 3: the matrix function is the fastest and most memory efficient for large n
See benchmark numbers in __main__ for performance comparisons/ See benchmark numbers in __main__ for performance comparisons/
https://en.wikipedia.org/wiki/Fibonacci_number for more information https://en.wikipedia.org/wiki/Fibonacci_number for more information
@ -17,6 +19,9 @@ from collections.abc import Iterator
from math import sqrt from math import sqrt
from time import time from time import time
import numpy as np
from numpy import ndarray
def time_func(func, *args, **kwargs): def time_func(func, *args, **kwargs):
""" """
@ -230,6 +235,88 @@ def fib_binet(n: int) -> list[int]:
return [round(phi**i / sqrt_5) for i in range(n + 1)] return [round(phi**i / sqrt_5) for i in range(n + 1)]
def matrix_pow_np(m: ndarray, power: int) -> ndarray:
"""
Raises a matrix to the power of 'power' using binary exponentiation.
Args:
m: Matrix as a numpy array.
power: The power to which the matrix is to be raised.
Returns:
The matrix raised to the power.
Raises:
ValueError: If power is negative.
>>> m = np.array([[1, 1], [1, 0]], dtype=int)
>>> matrix_pow_np(m, 0) # Identity matrix when raised to the power of 0
array([[1, 0],
[0, 1]])
>>> matrix_pow_np(m, 1) # Same matrix when raised to the power of 1
array([[1, 1],
[1, 0]])
>>> matrix_pow_np(m, 5)
array([[8, 5],
[5, 3]])
>>> matrix_pow_np(m, -1)
Traceback (most recent call last):
...
ValueError: power is negative
"""
result = np.array([[1, 0], [0, 1]], dtype=int) # Identity Matrix
base = m
if power < 0: # Negative power is not allowed
raise ValueError("power is negative")
while power:
if power % 2 == 1:
result = np.dot(result, base)
base = np.dot(base, base)
power //= 2
return result
def fib_matrix_np(n: int) -> int:
"""
Calculates the n-th Fibonacci number using matrix exponentiation.
https://www.nayuki.io/page/fast-fibonacci-algorithms#:~:text=
Summary:%20The%20two%20fast%20Fibonacci%20algorithms%20are%20matrix
Args:
n: Fibonacci sequence index
Returns:
The n-th Fibonacci number.
Raises:
ValueError: If n is negative.
>>> fib_matrix_np(0)
0
>>> fib_matrix_np(1)
1
>>> fib_matrix_np(5)
5
>>> fib_matrix_np(10)
55
>>> fib_matrix_np(-1)
Traceback (most recent call last):
...
ValueError: n is negative
"""
if n < 0:
raise ValueError("n is negative")
if n == 0:
return 0
m = np.array([[1, 1], [1, 0]], dtype=int)
result = matrix_pow_np(m, n - 1)
return int(result[0, 0])
if __name__ == "__main__": if __name__ == "__main__":
from doctest import testmod from doctest import testmod
@ -242,3 +329,4 @@ if __name__ == "__main__":
time_func(fib_memoization, num) # 0.0100 ms time_func(fib_memoization, num) # 0.0100 ms
time_func(fib_recursive_cached, num) # 0.0153 ms time_func(fib_recursive_cached, num) # 0.0153 ms
time_func(fib_recursive, num) # 257.0910 ms time_func(fib_recursive, num) # 257.0910 ms
time_func(fib_matrix_np, num) # 0.0000 ms