rrt@duke.cs.duke.edu (Russell R. Tuck) (06/22/88)
(I tried posting this reply some time ago to a query about parallel mandelbrot
algorithms. I didn't post quite correctly, and it never made it out. I'm
just getting time to try again.)
Pixel-Planes 4, a research machine at UNC Chapel Hill, computes 30
512x512 mandelbrot set images per second.
Pxpl4 (for short) is a SIMD machine with 256K 1-bit processors.
The mandelbrot program was written by Greg Turk, and computes both the
mandelbrot and julia sets every 1/30th of a second. This lets you fly
around them interactively. While you are moving around the sets, it
computes 25 iterations per image; when you stop it keeps iterating
(the image quits changing after less than a second).
The algorithm is very straightforward. There's a processor for every pixel,
so each processor just computes one point in the mandelbrot or julia set,
by ordinary methods.
Because pxpl4 has only 72 bits of memory per processor, it uses 16 bit
fixed point numbers instead of floating point numbers. This limits how
far you can zoom in on a small part of the set. (After a point, you
run out of precision: the pixels get bigger instead of showing infinitely
smaller features.)
There's a full description of Pixel-Planes in the proceedings of SIGGRAPH '85.
The paper is by Henry Fuchs, et al. Work is underway on a much faster
successor machine.
Russ
--
Russell R. Tuck, III ARPA: rrt@cs.duke.edu
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