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bd9464e4ac
* mandelbrot.py: Commenting out long running tests
* updating DIRECTORY.md
* Comment out 9 sec doctests
* Update bidirectional_breadth_first_search.py
* Comment out slow tests
* Comment out slow (9.15 sec) pytests...
* # Comment out slow (4.20s call) doctests
* Comment out slow (3.45s) doctests
* Update miller_rabin.py
* Update miller_rabin.py
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52 lines
1.3 KiB
Python
52 lines
1.3 KiB
Python
import random
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from .binary_exp_mod import bin_exp_mod
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# This is a probabilistic check to test primality, useful for big numbers!
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# if it's a prime, it will return true
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# if it's not a prime, the chance of it returning true is at most 1/4**prec
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def is_prime(n, prec=1000):
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"""
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>>> from .prime_check import prime_check
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>>> # all(is_prime(i) == prime_check(i) for i in range(1000)) # 3.45s
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>>> all(is_prime(i) == prime_check(i) for i in range(256))
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True
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"""
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if n < 2:
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return False
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if n % 2 == 0:
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return n == 2
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# this means n is odd
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d = n - 1
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exp = 0
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while d % 2 == 0:
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d /= 2
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exp += 1
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# n - 1=d*(2**exp)
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count = 0
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while count < prec:
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a = random.randint(2, n - 1)
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b = bin_exp_mod(a, d, n)
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if b != 1:
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flag = True
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for i in range(exp):
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if b == n - 1:
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flag = False
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break
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b = b * b
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b %= n
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if flag:
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return False
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count += 1
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return True
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if __name__ == "__main__":
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n = abs(int(input("Enter bound : ").strip()))
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print("Here's the list of primes:")
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print(", ".join(str(i) for i in range(n + 1) if is_prime(i)))
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