xfroot(1) xfroot(1)
21 September 1989
NAME
xfroot - set fractal root window (monochrome)
SYNOPSIS
xfroot [-p n] [-P n] [-a r] [-b r] [-c r] [-display display]
DESCRIPTION
Xfroot sets the X root window to display a monochrome fractal. The
fractal algorithm was published in A. K. Dewdney's Computer
Recreations column in the September 1986 Scientific American and
attributed to Barry Martin of Aston University, Birmingham, England.
OPTIONS
-p -P
Sets maximum points to calculate to n. -p sets the maximum for
in-range (i.e. on display) points. -P sets the total points to
calculate. Defaults: -p: 25% of pixels in server display. -P: 3
times the -p value.
-a -b -c
Sets the corresponding fractal algorithm parameter to the real
value r. Interesting values seem to be in the range -1000 < r <
1000. The algorithm seems sensitive to changes in the values out
to the precision (double) of the arithmetic, about 16 significant
digits. By default, random values are assigned.
SPECIAL CONSIDERATIONS
With the default parameters, xfroot calculates hundreds of thousands
of points. Each point requires a double precision square root,
multiply and three or four subtracts, plus integer arithmetic to
determine if the point is in range and store the point in a bit map.
Since each point depends on the value for the previous point, the
calculation does not lend itself to vectorizing or parallelization.
The following table is a rough guide to the amount of processor time
involved. It gives ranges of fractal points per uniprocessor second
measured on a variety of client hosts. The lower values for a
processor reflect the case when all or most points are in in-range and
require bit-manipulation to record the point.
Cray X-MP: 157,000 to 194,000 *
Cray 2: 129,000 to 183,000 *
Convex C200: 41,000 to 47,000 *
Vaxserver 3500: 13,200 to 15,200
Sequent Symmetry: 9,900 to 10,500 *
Vaxstation 2000: 4,670 to 5,530
Sun 3/60: 1,960 to 2,060
Sun 3/50: 1,270 to 1,330
(* = per processor)
- 1 - Formatted: December 15, 2025
xfroot(1) xfroot(1)
21 September 1989
AUTHORS
Ed Kubaitis, Computing Services Office, University of Illinois. The
Xlib code to set the root screen was adapted from code in xphoon by
Jef Poskanzer and Craig Leres, and carries the following copyright:
Copyright (C) 1988 by Jef Poskanzer and Craig Leres. Permission to
use, copy, modify, and distribute this software and its documentation
for any purpose and without fee is hereby granted, provided that the
above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation. This software is provided "as is" without express or
implied warranty.
- 2 - Formatted: December 15, 2025
