langs-performance/primes.py

import os
import sys
import time


def get_primes7(n):
    """
    standard optimized sieve algorithm to get a list of prime numbers
    --- this is the function to compare your functions against! ---
    """
    if n < 2:
        return []
    if n == 2:
        return [2]
    # do only odd numbers starting at 3
    if sys.version_info.major <= 2:
        s = range(3, n + 1, 2)
    else:  # Python 3
        s = list(range(3, n + 1, 2))
    # n**0.5 simpler than math.sqr(n)
    mroot = n ** 0.5
    half = len(s)
    i = 0
    m = 3
    while m <= mroot:
        if s[i]:
            j = (m * m - 3) // 2  # int div
            s[j] = 0
            while j < half:
                s[j] = 0
                j += m
        i = i + 1
        m = 2 * i + 3
    return [2] + [x for x in s if x]

start_time = int(time.time())
period_time = int(os.environ['RUN_TIME'])

while (int(time.time()) - start_time) < period_time:
    res = get_primes7(10000000)
    print("Found {} prime numbers.".format(len(res)))