Subversion Repositories ca_prng

#!/usr/bin/env python

# -*- coding: utf-8 -*-

#=======================================================================

#

# ca_prng.py

# ---------

# Fast and simple ca_prng conformant cellular automata model in

# Python. This model is actually implented as a general 1D CA class

# and the rule and size of the CA array is provided as parameters.

# 

# 

# Author: Joachim Strömbergson

# Copyright (c) 2008, Kryptologik

# All rights reserved.

#

# Redistribution and use in source and binary forms, with or without

# modification, are permitted provided that the following conditions

# are met:

#     * Redistributions of source code must retain the above copyright

#       notice, this list of conditions and the following disclaimer.

# 

#     * Redistributions in binary form must reproduce the above

#       copyright notice, this list of conditions and the following

#       disclaimer in the documentation and/or other materials

#       provided with the distribution.

#

# THIS SOFTWARE IS PROVIDED BY Kryptologik ''AS IS'' AND ANY EXPRESS

# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

# ARE DISCLAIMED. IN NO EVENT SHALL Kryptologik BE LIABLE FOR ANY

# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

# GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#

#=======================================================================

#-------------------------------------------------------------------

# Python module imports.

#-------------------------------------------------------------------

import sys

import math

import optparse

#-------------------------------------------------------------------

# class CellularAutomata()

# 

# This class implements a 1D cellular automata. The class expects

# to be initalized with an array of arbitrary length with initial

# cell state values (0 or 1) as well as an array with update rules.

# 

# The update rule is expected to contain eight values (0 or 1)

# that define the update value for a cell given by the current

# state of the cell and two nearest neighbours. Note that nearest

# neighbour is calculated with wrap around, that is the cell

# array is treated as a ring.

#-------------------------------------------------------------------

class CellularAutomata():

    def __init__(self, rule, init_state, verbosity):

        self.my_rule = rule

        self.my_state = init_state

        self.verbose = verbosity

    def print_state(self):

        """Print the current state of the cellular automata."""

        print self.my_state

    def update_ca_state(self):

        """Update the cells in the cellular automata array."""

        # Create a new CA array to store the updated state.

        new_state = [x for x in range(len(self.my_state))]

        # For each cell we extract three consequtive bits from the

        # current state and use wrap around at the edges.

        for curr_bit in range(len(self.my_state)):

            if curr_bit == 0:

                bit_left = self.my_state[-1]

                bit_mid = self.my_state[0]

                bit_right = self.my_state[1]

            elif curr_bit == (len(self.my_state) - 1):

                bit_left = self.my_state[(curr_bit - 1)]

                bit_mid = self.my_state[curr_bit]

                bit_right = self.my_state[0]

            else:

                bit_left = self.my_state[(curr_bit - 1)]

                bit_mid = self.my_state[curr_bit]

                bit_right = self.my_state[(curr_bit + 1)]

            # Use the extraxted bits to calculate an index for

            # the update rule array and update the cell.

            rule_index = 4 * bit_left + 2 * bit_mid + bit_right

            if self.verbose:

                print "rule_index = %d " % rule_index

            new_state[curr_bit] = self.my_rule[rule_index]

        # Replace the old state array with the new array.

        self.my_state = new_state

#-------------------------------------------------------------------

# main()

#

# Main function.

#-------------------------------------------------------------------

def main():

    # Create an update rule array. This is Wolframs rule 30.

    # We also create a CA array with a given init state.

    my_update_rules = [0, 1, 1, 1, 1, 0, 0, 0]

    my_init_state = [1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0]

    # Create a CA object.

    my_ca = CellularAutomata(my_update_rules, my_init_state, False)

    # Run a few iterations printing the state before each update.

    for iteration in range(1000):

        my_ca.print_state()

        my_ca.update_ca_state()

#-------------------------------------------------------------------

# __name__

# Python thingy which allows the file to be run standalone as

# well as parsed from within a Python interpreter.

#-------------------------------------------------------------------

if __name__=="__main__":

    # Run the main function.

    sys.exit(main())

#=======================================================================

# EOF ca_prng.py

#=======================================================================