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# I found this example for PyCuda here:
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# http://wiki.tiker.net/PyCuda/Examples/Mandelbrot
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# I adapted it for PyOpenCL. Hopefully it is useful to someone.
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# July 2010, HolgerRapp@gmx.net
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# Original readme below these lines.
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# Mandelbrot calculate using GPU, Serial numpy and faster numpy
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# Use to show the speed difference between CPU and GPU calculations
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# ian@ianozsvald.com March 2010
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# Based on vegaseat's TKinter/numpy example code from 2006
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# http://www.daniweb.com/code/snippet216851.html#
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# with minor changes to move to numpy from the obsolete Numeric
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import numpy.linalg as la
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# You can choose a calculation routine below (calc_fractal), uncomment
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# one of the three lines to test the three variations
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# Speed notes are listed in the same place
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# set width and height of window, more pixels take longer to calculate
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def calc_fractal_opencl(q, maxiter):
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ctx = cl.Context(cl.get_platforms()[0].get_devices())
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queue = cl.CommandQueue(ctx)
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output = np.empty(q.shape, dtype=np.uint64)# resize(np.array(0,), q.shape)
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q_opencl = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=q)
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output_opencl = cl.Buffer(ctx, mf.WRITE_ONLY, output.nbytes)
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prg = cl.Program(ctx, """
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__kernel void mandelbrot(__global float2 *q,
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__global long *output, long const maxiter)
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int gid = get_global_id(0);
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float nreal, real = 0;
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for(int curiter = 0; curiter < maxiter; curiter++) {
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nreal = real*real - imag*imag + q[gid][0];
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imag = 2* real*imag + q[gid][1];
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if (real*real + imag*imag > 4.) {
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output[gid] = curiter;
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prg.mandelbrot(queue, output.shape, None, q_opencl,
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output_opencl, np.int32(maxiter))
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cl.enqueue_read_buffer(queue, output_opencl, output).wait()
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def calc_fractal_serial(q, maxiter):
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# calculate z using numpy
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# this routine unrolls calc_fractal_numpy as an intermediate
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# step to the creation of calc_fractal_opencl
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# it runs slower than calc_fractal_numpy
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z = np.zeros(q.shape, np.complex64)
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output = np.resize(np.array(0,), q.shape)
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for i in range(len(q)):
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for iter in range(maxiter):
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z[i] = z[i]*z[i] + q[i]
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def calc_fractal_numpy(q, maxiter):
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# calculate z using numpy, this is the original
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# routine from vegaseat's URL
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output = np.resize(np.array(0,), q.shape)
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z = np.zeros(q.shape, np.complex64)
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for iter in range(maxiter):
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done = np.greater(abs(z), 2.0)
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q = np.where(done,0+0j, q)
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z = np.where(done,0+0j, z)
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output = np.where(done, iter, output)
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# choose your calculation routine here by uncommenting one of the options
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calc_fractal = calc_fractal_opencl
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# calc_fractal = calc_fractal_serial
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# calc_fractal = calc_fractal_numpy
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if __name__ == '__main__':
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class Mandelbrot(object):
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self.root.title("Mandelbrot Set")
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def draw(self, x1, x2, y1, y2, maxiter=300):
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# draw the Mandelbrot set, from numpy example
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xx = np.arange(x1, x2, (x2-x1)/w*2)
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yy = np.arange(y2, y1, (y1-y2)/h*2) * 1j
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q = np.ravel(xx+yy[:, np.newaxis]).astype(np.complex64)
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start_main = time.time()
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output = calc_fractal(q, maxiter)
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end_main = time.time()
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secs = end_main - start_main
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print "Main took", secs
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output = (output + (256*output) + (256**2)*output) * 8
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# convert output to a string
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self.mandel = output.tostring()
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def create_image(self):
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create the image from the draw() string
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self.im = Image.new("RGB", (w/2, h/2))
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# you can experiment with these x and y ranges
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self.draw(-2.13, 0.77, -1.3, 1.3)
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self.im.fromstring(self.mandel, "raw", "RGBX", 0, -1)
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def create_label(self):
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# put the image on a label widget
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self.image = ImageTk.PhotoImage(self.im)
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self.label = tk.Label(self.root, image=self.image)
added
removed
examples/demo_mandelbrot.py
