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#!/usr/bin/env osh
#
# Compute an image of the Mandelbrot set. This is a benchmark
# program. It isn't intended that it be the most efficient
# implementation, we just want to stress the numerical
# routines.
#
# It generates a pgm image. You can use the ppm tools, or xv,
# to view the result.
#
.LANGUAGE: program
#
# Program constants
# dimen: the dimension of the image
# bound: the maximum value for each pixel
#
dimen = 128
bound = 255
#
# Fixed-point numbers.
#
fix-shift = 24
fix-int(i) =
value i << fix-shift
fix-add(i, j) =
value i + j
fix-sub(i, j) =
value i - j
fix-mul(i, j) =
return ((i >> (fix-shift / 2)) * (j >> (fix-shift / 2)))
fix-mul-int(i, j) =
value i * j
fix-div-int(i, j) =
value i / j
#
# Compute a point in the Mandelbrot set.
#
compute(x, y) =
loop(k, usex, usey) =
if k = 0
value k
else
xsqr = fix-mul(usex, usex)
ysqr = fix-mul(usey, usey)
if fix-add(xsqr, ysqr) > fix-int(4)
value k
else
new-usey = fix-add(fix-mul(fix-int(2), fix-mul(usex, usey)), y)
new-usex = fix-add(fix-sub(xsqr, ysqr), x)
loop(k - 1, new-usex, new-usey)
loop(bound, x, y)
#
# Main function
# Plot the Mandelbrot set at position (x, y).
# the dimension of the image is scale. The arguments are
# fixpoint numbers.
#
mandel(x, y, scale) =
left = fix-sub(x, fix-div-int(scale, 2))
top = fix-sub(y, fix-div-int(scale, 2))
step = fix-div-int(scale, dimen)
println($"""P2
""""""""# Creator mandel.om
""""""""$(dimen)
""""""""$(dimen)
""""""""255
""")
i = 0
while i < dimen
j = 0
line[] =
while j < dimen
x = fix-add(left, fix-mul-int(step, i))
y = fix-add(top, fix-mul-int(step, j))
line[] += compute(x, y)
j = j + 1
println($"$(line)")
i = i + 1
stdout = fopen($'mandel.ppm', $'w')
mandel(fix-int(-1), 0, fix-int(2))
close(stdout)
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