mandelbrot-non-working.py

#! /usr/bin/env python
"""
Non-working example implementation of the Mandelbort fractal 
using the TensorFlow API.
"""

import numpy as np
import tensorflow as tf

from tensorflow import (
    constant as C_,
    Variable as V_,
    placeholder as X_,
)

def mandelbrot(x, y):
    """
    Compute number of iterations of the Mandelbrot function at (x,y).
    """
    g, in_, out_ = mandelbrot_()
    x_in, y_in = in_
    n_out, x_out, y_out = out_
    with tf.Session(graph=g).as_default() as session:
        # initialize vars with null values
        feed0 = { x_in:0.0, y_in:0.0 }
        session.run(n_out.initializer, feed0)
        session.run(x_out.initializer, feed0)
        session.run(y_out.initializer, feed0)
        # run the graph at the chosen point
        feed = { x_in:x, y_in:y }
        n_out, x_out, y_out = session.run(out_, feed)
        print("({0},{1}): {2}".format(x, y, [n_out, x_out, y_out]))


def mandelbrot_(maxiter=255):
    """
    Return graph computing the Mandelbrot set at (x,y).
    """
    graph = tf.Graph()
    with graph.as_default():
        # input placeholders
        x = X_(tf.float32, shape=[], name='x_in')
        y = X_(tf.float32, shape=[], name='y_in')

        # output variables
        n_ = V_(0, tf.int32,   name='n')
        x_ = V_(x, tf.float32, name='x')
        y_ = V_(y, tf.float32, name='y')

        # main loop
        i_ = tf.constant(0)
        def cond(i_, z_re_, z_im_):
            return tf.logical_and(
                tf.less(i_, maxiter),
                (z_re_*z_re_ + z_im_*z_im_) < 4)
        def body(i_, z_re_, z_im_):
            return [
                i_+1,                          # iteration count
                z_re_*z_re_ - z_im_*z_im_ + x, # real part of z
                2*z_re_*z_im_ + y,             # imag part of z
            ]
        l = tf.while_loop(cond, body, [i_, x, y],
                          parallel_iterations=1)
        with tf.control_dependencies(l):
            n_.assign(l[0])
            x_.assign(l[1])
            y_.assign(l[2])

    return (
        graph,       # graph
        (x, y),      # inputs
        (n_, x_, y_) # outputs
    )


#
# main
#

if __name__ == '__main__':
    mandelbrot(0.25, -0.15)

mandelbrot-working.py

#! /usr/bin/env python
"""
Working example implementation of the Mandelbort fractal 
using the TensorFlow API.
"""

import numpy as np
import tensorflow as tf

from tensorflow import (
    constant as C_,
    Variable as V_,
    placeholder as X_,
)

def mandelbrot(x, y):
    """
    Compute number of iterations of the Mandelbrot function at (x,y).
    """
    g, in_, out_ = mandelbrot_()
    x_in, y_in = in_
    n_out, x_out, y_out = out_
    with tf.Session(graph=g).as_default() as session:
        # (a)
        # run the graph at the chosen point
        feed = { x_in:x, y_in:y }
        n_out, x_out, y_out = session.run(out_, feed)
        print("({0},{1}): {2}".format(x, y, [n_out, x_out, y_out]))


def mandelbrot_(maxiter=255):
    """
    Return graph computing the Mandelbrot set at (x,y).
    """
    graph = tf.Graph()
    with graph.as_default():
        # input placeholders
        x = X_(tf.float32, shape=[], name='x_in')
        y = X_(tf.float32, shape=[], name='y_in')

        # output variables
        n_ = V_(0, tf.int32,   name='n')
        x_ = V_(x, tf.float32, name='x')
        y_ = V_(y, tf.float32, name='y')

        # main loop
        i_ = tf.constant(0)
        def cond(i_, z_re_, z_im_):
            return tf.logical_and(
                tf.less(i_, maxiter),
                (z_re_*z_re_ + z_im_*z_im_) < 4)
        def body(i_, z_re_, z_im_):
            return [
                i_+1,                          # iteration count
                z_re_*z_re_ - z_im_*z_im_ + x, # real part of z
                2*z_re_*z_im_ + y,             # imag part of z
            ]
        l = tf.while_loop(cond, body, [i_, x, y],
                          parallel_iterations=1)
        # (b)
        n_, x_, y_ = l

    return (
        graph,       # graph
        (x, y),      # inputs
        (n_, x_, y_) # outputs
    )


#
# main
#

if __name__ == '__main__':
    mandelbrot(0.25, -0.15)