MT.py

#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""
Based on the pseudocode in https://en.wikipedia.org/wiki/Mersenne_Twister. Generates uniformly distributed 32-bit integers in the range [0, 232 − 1] with the MT19937 algorithm

Yaşar Arabacı <yasar11732 et gmail nokta com>
"""


class MersenneTwister(object):
    MT = []
    index = 0
    bitmask_1 = 0
    bitmask_2 = 0
    bitmask_3 = 0

    def __init__(self, seed):
        """Initialize the generator from a seed"""
        # Create a length 624 list to store the state of the generator
        self.MT = [0 for i in xrange(624)]
        self.index = 0

        # To get last 32 bits
        self.bitmask_1 = (2 ** 32) - 1

        # To get 32. bit
        self.bitmask_2 = 2 ** 31

        # To get last 31 bits
        self.bitmask_3 = (2 ** 31) - 1

        self.MT[0] = seed
        for i in xrange(1, 624):
            self.MT[i] = (1812433253 * (self.MT[i-1] ^ (self.MT[i-1] >> 30)) + i) & 0xFFFFFFFF

    def extract_number(self):
        """
        Extract a tempered pseudorandom number based on the index-th value,
        calling generate_numbers() every 624 numbers
        """
        if self.index == 0:
            self.generate_numbers()
        y = self.MT[self.index]
        y ^= y >> 11
        y ^= (y << 7) & 2636928640
        y ^= (y << 15) & 4022730752
        y ^= y >> 18

        self.index = (self.index + 1) % 624
        return y

    def generate_numbers(self):
        """Generate an array of 624 untempered numbers"""
        for i in xrange(624):
            y = (self.MT[i] & self.bitmask_2) + (self.MT[(i + 1 ) % 624] & self.bitmask_3)
            self.MT[i] = self.MT[(i + 397) % 624] ^ (y >> 1)
            if y % 2 != 0:
                self.MT[i] ^= 2567483615

"""
if __name__ == "__main__":
    from datetime import datetime
    now = datetime.now()
    initialize_generator(now.microsecond)
    for i in xrange(100):
        "Print 100 random numbers as an example"
        print extract_number()
"""