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 xfroot(1)                                                         xfroot(1)
                              21 September 1989

      xfroot - set fractal root window (monochrome)

      xfroot  [-p n] [-P n] [-a r] [-b r] [-c r] [-display display]

      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.

      -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.

      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:  July 7, 2022

 xfroot(1)                                                         xfroot(1)
                              21 September 1989

      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:  July 7, 2022