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README
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1988-09-14
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For those who have installed Inboard 386s in their systems but haven't
run any 32-bit code yet (not too many around), I am uploading FR386, a
Mandelbrot Set generating program. If you are not familiar with the Mandel-
brot Set, refer to the August 1985 issue of Scientific American. A.K.
Dewdney's column, "Computer Recreations", has a very good introduction on
what the Mandelbrot Set is and how to generate them.
FR386 was written by H.W. Stockman and uses 32-bit instructions and the
80386 32-bit registers to simulate 1 Megaflop performance without using a
math coprocessor. He uses fixed-point math to achieve this phenomenal speed.
Those of you who are familiar with programs of this type know that a math
coprocessor is essential to get decent execution speeds because they are
generally written in floating point and are computation intensive. I remember
one plot that took me over 42 hours to generate. In general, most plots take
anywhere from half an hour to several hours. You will be pleasantly surprised
to see how FR386 generates plots in minutes.
The program is discussed in detail in the Sept-Oct 1988 issue of Micro
Cornucopia Magazine (P.O. Box 223, Bend, Oregon 97709). If I remember right,
the magazine was started and is being run by an ex-Intel employee. The comp-
lete source code is available for downloading from the magazine's bulletin
board at (503) 382-7643.
I have included a another implementation of the same program so that you
can run it to compare the speed difference. This one is written by Bob Hay.
The two programs are not your full-featured Mandelbrot programs. For
one thing, neither has a "save" feature so that you will have to use one of
the commercially available graphics grabber programs if you want to save an
image. You don't have control over the colors in the different bands either.
However, for the most part the programs are adequate. I have tested them on
EGA and Hercules boards. Of course, they will also run on a VGA card in EGA
mode.
There is a slight technical flaw in the programs. The images are flipped
upside-down. It doesn't matter if the images are symmetrical about the X-axis.
If they're not, change the signs (+ to -, and - to +) on your Y parameters and
enter them as Ymin and Ymax, accordingly.
The full Mandelbrot set can be generated with the following parameters:
Xmin = -2.25, Xmax = +1.00, Ymin = -1.25, Ymax = +1.25. Try to keep maximum
number of iterations to around 256 for small magnifications to keep the execu-
tion times low.
If anybody wants more data on what parameters to use for some really
interesting plots, please contact me.
Hector Santos 9-14-88