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# I found this example for PyCuda here:
# http://wiki.tiker.net/PyCuda/Examples/Mandelbrot
#
# I adapted it for PyOpenCL. Hopefully it is useful to someone.
# July 2010, HolgerRapp@gmx.net
#
# Original readme below these lines.
# Mandelbrot calculate using GPU, Serial numpy and faster numpy
# Use to show the speed difference between CPU and GPU calculations
# ian@ianozsvald.com March 2010
# Based on vegaseat's TKinter/numpy example code from 2006
# http://www.daniweb.com/code/snippet216851.html#
# with minor changes to move to numpy from the obsolete Numeric
import numpy as np
import time
import numpy
import numpy.linalg as la
import pyopencl as cl
# You can choose a calculation routine below (calc_fractal), uncomment
# one of the three lines to test the three variations
# Speed notes are listed in the same place
# set width and height of window, more pixels take longer to calculate
w = 256
h = 256
def calc_fractal_opencl(q, maxiter):
ctx = cl.Context(cl.get_platforms()[0].get_devices())
queue = cl.CommandQueue(ctx)
output = np.empty(q.shape, dtype=np.uint16)
mf = cl.mem_flags
q_opencl = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=q)
output_opencl = cl.Buffer(ctx, mf.WRITE_ONLY, output.nbytes)
prg = cl.Program(ctx, """
#pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable
__kernel void mandelbrot(__global float2 *q,
__global ushort *output, ushort const maxiter)
{
int gid = get_global_id(0);
float nreal, real = 0;
float imag = 0;
output[gid] = 0;
for(int curiter = 0; curiter < maxiter; curiter++) {
nreal = real*real - imag*imag + q[gid].x;
imag = 2* real*imag + q[gid].y;
real = nreal;
if (real*real + imag*imag > 4.0f)
output[gid] = curiter;
}
}
""").build()
prg.mandelbrot(queue, output.shape, (64,), q_opencl,
output_opencl, np.uint16(maxiter))
cl.enqueue_read_buffer(queue, output_opencl, output).wait()
return output
def calc_fractal_serial(q, maxiter):
# calculate z using numpy
# this routine unrolls calc_fractal_numpy as an intermediate
# step to the creation of calc_fractal_opencl
# it runs slower than calc_fractal_numpy
z = np.zeros(q.shape, np.complex64)
output = np.resize(np.array(0,), q.shape)
for i in range(len(q)):
for iter in range(maxiter):
z[i] = z[i]*z[i] + q[i]
if abs(z[i]) > 2.0:
q[i] = 0+0j
z[i] = 0+0j
output[i] = iter
return output
def calc_fractal_numpy(q, maxiter):
# calculate z using numpy, this is the original
# routine from vegaseat's URL
output = np.resize(np.array(0,), q.shape)
z = np.zeros(q.shape, np.complex64)
for iter in range(maxiter):
z = z*z + q
done = np.greater(abs(z), 2.0)
q = np.where(done,0+0j, q)
z = np.where(done,0+0j, z)
output = np.where(done, iter, output)
return output
# choose your calculation routine here by uncommenting one of the options
calc_fractal = calc_fractal_opencl
# calc_fractal = calc_fractal_serial
# calc_fractal = calc_fractal_numpy
if __name__ == '__main__':
import Tkinter as tk
import Image # PIL
import ImageTk # PIL
class Mandelbrot(object):
def __init__(self):
# create window
self.root = tk.Tk()
self.root.title("Mandelbrot Set")
self.create_image()
self.create_label()
# start event loop
self.root.mainloop()
def draw(self, x1, x2, y1, y2, maxiter=30):
# draw the Mandelbrot set, from numpy example
xx = np.arange(x1, x2, (x2-x1)/w)
yy = np.arange(y2, y1, (y1-y2)/h) * 1j
q = np.ravel(xx+yy[:, np.newaxis]).astype(np.complex64)
start_main = time.time()
output = calc_fractal(q, maxiter)
end_main = time.time()
secs = end_main - start_main
print "Main took", secs
self.mandel = (output.reshape((h,w)) /
float(output.max()) * 255.).astype(np.uint8)
def create_image(self):
""""
create the image from the draw() string
"""
# you can experiment with these x and y ranges
self.draw(-2.13, 0.77, -1.3, 1.3)
self.im = Image.fromarray(self.mandel)
self.im.putpalette(reduce(
lambda a,b: a+b, ((i,0,0) for i in range(255))
))
def create_label(self):
# put the image on a label widget
self.image = ImageTk.PhotoImage(self.im)
self.label = tk.Label(self.root, image=self.image)
self.label.pack()
# test the class
test = Mandelbrot()
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