NAME

       hp - simulate the hodgepodge machine

SYNOPSIS

       hp -help
         or
       hp     [-width  integer]  [-height integer] [-states inte-
              ger]  [-steps  integer]  [-seed  integer]   [-diag]
              [-wrap]  [-g  double]  [-k1  double]  [-k2  double]
              [-freq  integer]  [-inv]  [-mag   integer]   [-term
              string]

DESCRIPTION

       The  time evolution of the hodgepodge machine is simulated
       and plotted according to the  specified  parameters.   The
       neighborhood  of  a  cell  can  optionally  include or not
       include diagonal cells  in  a  3x3  area;   Moreover,  the
       neighborhood  can  also  wrap around the edges so that the
       grid is topologically toroidal.  With a proper  choice  of
       parameters, this system resembles the Belousov-Zhabotinsky
       reaction which forms self-perpetuating spirals in  a  lat-
       tice.   See  the  RULES section of the manual pages or the
       source code for an explanation of  how  the  cells  change
       over time.

OPTIONS

       -width integer
              Width of the plot in pixels.

       -height integer
              Height of the plot in pixels.

       -states integer
              Number of cell states.

       -steps integer
              Number of simulated steps.

       -seed integer
              Random seed for initial state.

       -diag  Diagonal cells are neighbors?

       -wrap  Use a wrap-around space?

       -g double
              Infection progression rate.

       -k1 double
              First weighting parameter.

       -k2 double
              Second weighting parameter.


       -freq integer
              Plot frequency.

       -inv   Invert all colors?

       -mag integer
              Magnification factor.

       -term string
              How to plot points.

RULES

       If  each cell can be in one of N states (labelled 0 to n -
       1), then cells in state 0 are ``healthy,'' cells in  state
       n - 1 are ``ill,'' and all other cells are ``infected.''

       Within  a  cell's  neighborhood,  let  Nill,  Ninf, and S,
       denote the number of ill cells,  the  number  of  infected
       cells,  and  the  sum  of the states of all neighbors plus
       this cell's state.  The next state is  determined  by  the
       three rules:

          Healthy: floor( Ninf / k1 ) + floor( Nill / k2 )

          Infected: floor( S / ( Ninf + 1 ) ) + g

          Ill: magically becomes healthy, thus 0.

       Where  k1,  k2,  and g are the parameters specified by the
       command line options.

MISCELLANY

       If you move from (to) an 8 cell neighborhood to (from) a 4
       cell  neighborhood try dividing (multiplying) k1 and k2 by
       2 to produce a similar time evolution that  occurred  with
       the previous neighborhood size.

       For some reason, 4 cell neighborhoods seem to produce pat-
       terns with more spirals.

       This simulation can be frustratingly slow at times, so you
       may  wish to use the -freq option to cut down on the over-
       head of plotting the states.

BUGS

       No sanity checks are performed to make sure  that  any  of
       the options make sense.

AUTHOR

       Copyright (c) 1997, Gary William Flake.

       Permission  granted  for any use according to the standard
       GNU ``copyleft'' agreement provided that the author's com-
       ments  are  neither  modified nor removed.  No warranty is

       given or implied.