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StarInfo/Lurcock/!Hodge/!Help

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The HodgePodge Machine - a 2-dimensional cellular automaton
� 1996 Pontus Lurcock
=============================================================================

INTRODUCTION_________________________________________________________________

The Hodgepodge Machine is a family of cellular automata invented by Gerhardt
and Schuster at the university of Bielefeld. It produces swirly patterns.
!Hodge is a multitasking implementation of this system, letting you play
around with the settings to produce varied results...


WHAT IT IS___________________________________________________________________

The action takes place on a grid of square cells, each of which has a state
corresponding to a number from 0 to n, n being the highest possible state. In
!Hodge the grid is a sprite, each cell is a pixel, and the cell's state is
represented by the pixel's colour.

Time moves in steps of one generation. The state of a cell in any generation
is entirely dependent on the state of itself and its neighbours in the
previous generations, as well as a few predefined constants.

In the Hodgepodge machine, a cell with state 0 is 'healthy', a cell with
state n (i.e. maximum state) is 'ill', and anything in between in 
is 'infected'. The method used to calculate the cell's state in the next
generation depends on which of these three categories it is in:

For a healthy cell:   new state = INT(A/k1) + INT(B/k2)
For an infected cell: new state = INT(S/A) + g
For an ill cell:      new state = 0 (cell miraculously becomes healthy)

A is the number of infected neighbouring cells (including the cell itself)
B is the number of ill neighbouring cells
S is the sum of the states of the cell and its neighbours
k1, k2 and g are constants

A great range of behaviour can be produced just by changing k1, k2 and g. But
there's more. You can also control what is meant by 'neighbours'. Normally
this means either the four cells above, below, left and right of the cell
(von Neumann neighbourhood), or the eight cells touching the cell (Moore
neighbourhood), but !Hodge lets you select any combination of the eight
surrounding cells. (see illustration below)

  #  von Neumann      ### Moore         # # Don't know what this is called,
 #O#                  #O#                O  but it produces interesting
  #                   ###               # # results...

The only other thing you can change (apart from the size) is the wrapping. If
'wrap' is on, a cell at the edge of the grid will 'see' the cell at the
opposite edge as its neighbour. Wrapped automata tile seamlessly, so they
make rather nice backdrops...


TOOLS________________________________________________________________________

Clicking select on the Hodge icon brings up the main display window with a
toolbar. From left to right, the tools are:

||  PAUSE: Stops the automaton.
>   PLAY:  Starts it.
|>  STEP:  Advances one generation.
>[] FULL:  Single-tasks, scaling the picture up to full screen.
#   RESET: Randomises the grid.

At the right is an icon showing the current generation.
While in single-tasking mode, you can return to the desktop by pressing any
key or mouse button. However, note that the keyboard is only scanned once a
generation so you may have to hold it down slightly...
Clicking menu over the display lets you change the magnification and save the
current generation.

The Settings window, accessed via the icon bar menu (or click adjust on the
icon), should be fairly self-explanatory. The width and height must be
between 20 and 512, and a multiple of 4. The grid is randomised every time
the rules are changed.


NOTES________________________________________________________________________

!Hodge tends to slow the desktop down somewhat. Even on a Risc PC things
start getting a bit jerky above a size of around 80x80.

In rectangular-pixel modes the x scale is doubled when plotting, so the cells
don't look stretched.

The speed-critical update routine is written in Assembler, and is custom-
reassembled every time the settings are changed - this frees up the registers
which would otherwise be needed to hold things like constants and grid size.
The grid is stored in two 256-colour sprites, which are easy to access since
they're one byte per pixel. (Two are required because you don't want to start
overwriting the old generation before you've finished reading it). One or two
mildly cunning techniques are used for speed, but it's fairly straightforward
really...

Interesting results can be producd with a von Neumann neighbourhood, n=100,
k1=2, k2=3, g=18 or thereabouts. Apparently it looks a bit like certain
oscillating chemical reactions...


CONTACT______________________________________________________________________

pontus@arcade.demon.co.uk, or 9 Monmouth Road, Oxford OX1 4TD, England

Happing hodging...

Pont
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00000040  39 36 20 50 6f 6e 74 75  73 20 4c 75 72 63 6f 63  |96 Pontus Lurcoc|
00000050  6b 0a 3d 3d 3d 3d 3d 3d  3d 3d 3d 3d 3d 3d 3d 3d  |k.==============|
00000060  3d 3d 3d 3d 3d 3d 3d 3d  3d 3d 3d 3d 3d 3d 3d 3d  |================|
*
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*
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000008c0  20 20 20 20 20 20 23 4f  23 20 20 20 20 20 20 20  |      #O#       |
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00000a30  54 4f 4f 4c 53 5f 5f 5f  5f 5f 5f 5f 5f 5f 5f 5f  |TOOLS___________|
00000a40  5f 5f 5f 5f 5f 5f 5f 5f  5f 5f 5f 5f 5f 5f 5f 5f  |________________|
*
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00000c90  79 6f 75 20 6d 61 79 20  68 61 76 65 20 74 6f 20  |you may have to |
00000ca0  68 6f 6c 64 20 69 74 20  64 6f 77 6e 20 73 6c 69  |hold it down sli|
00000cb0  67 68 74 6c 79 2e 2e 2e  0a 43 6c 69 63 6b 69 6e  |ghtly....Clickin|
00000cc0  67 20 6d 65 6e 75 20 6f  76 65 72 20 74 68 65 20  |g menu over the |
00000cd0  64 69 73 70 6c 61 79 20  6c 65 74 73 20 79 6f 75  |display lets you|
00000ce0  20 63 68 61 6e 67 65 20  74 68 65 20 6d 61 67 6e  | change the magn|
00000cf0  69 66 69 63 61 74 69 6f  6e 20 61 6e 64 20 73 61  |ification and sa|
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00000d10  65 6e 65 72 61 74 69 6f  6e 2e 0a 0a 54 68 65 20  |eneration...The |
00000d20  53 65 74 74 69 6e 67 73  20 77 69 6e 64 6f 77 2c  |Settings window,|
00000d30  20 61 63 63 65 73 73 65  64 20 76 69 61 20 74 68  | accessed via th|
00000d40  65 20 69 63 6f 6e 20 62  61 72 20 6d 65 6e 75 20  |e icon bar menu |
00000d50  28 6f 72 20 63 6c 69 63  6b 20 61 64 6a 75 73 74  |(or click adjust|
00000d60  20 6f 6e 20 74 68 65 0a  69 63 6f 6e 29 2c 20 73  | on the.icon), s|
00000d70  68 6f 75 6c 64 20 62 65  20 66 61 69 72 6c 79 20  |hould be fairly |
00000d80  73 65 6c 66 2d 65 78 70  6c 61 6e 61 74 6f 72 79  |self-explanatory|
00000d90  2e 20 54 68 65 20 77 69  64 74 68 20 61 6e 64 20  |. The width and |
00000da0  68 65 69 67 68 74 20 6d  75 73 74 20 62 65 0a 62  |height must be.b|
00000db0  65 74 77 65 65 6e 20 32  30 20 61 6e 64 20 35 31  |etween 20 and 51|
00000dc0  32 2c 20 61 6e 64 20 61  20 6d 75 6c 74 69 70 6c  |2, and a multipl|
00000dd0  65 20 6f 66 20 34 2e 20  54 68 65 20 67 72 69 64  |e of 4. The grid|
00000de0  20 69 73 20 72 61 6e 64  6f 6d 69 73 65 64 20 65  | is randomised e|
00000df0  76 65 72 79 20 74 69 6d  65 0a 74 68 65 20 72 75  |very time.the ru|
00000e00  6c 65 73 20 61 72 65 20  63 68 61 6e 67 65 64 2e  |les are changed.|
00000e10  0a 0a 0a 4e 4f 54 45 53  5f 5f 5f 5f 5f 5f 5f 5f  |...NOTES________|
00000e20  5f 5f 5f 5f 5f 5f 5f 5f  5f 5f 5f 5f 5f 5f 5f 5f  |________________|
*
00000e60  0a 0a 21 48 6f 64 67 65  20 74 65 6e 64 73 20 74  |..!Hodge tends t|
00000e70  6f 20 73 6c 6f 77 20 74  68 65 20 64 65 73 6b 74  |o slow the deskt|
00000e80  6f 70 20 64 6f 77 6e 20  73 6f 6d 65 77 68 61 74  |op down somewhat|
00000e90  2e 20 45 76 65 6e 20 6f  6e 20 61 20 52 69 73 63  |. Even on a Risc|
00000ea0  20 50 43 20 74 68 69 6e  67 73 0a 73 74 61 72 74  | PC things.start|
00000eb0  20 67 65 74 74 69 6e 67  20 61 20 62 69 74 20 6a  | getting a bit j|
00000ec0  65 72 6b 79 20 61 62 6f  76 65 20 61 20 73 69 7a  |erky above a siz|
00000ed0  65 20 6f 66 20 61 72 6f  75 6e 64 20 38 30 78 38  |e of around 80x8|
00000ee0  30 2e 0a 0a 49 6e 20 72  65 63 74 61 6e 67 75 6c  |0...In rectangul|
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00000f00  68 65 20 78 20 73 63 61  6c 65 20 69 73 20 64 6f  |he x scale is do|
00000f10  75 62 6c 65 64 20 77 68  65 6e 20 70 6c 6f 74 74  |ubled when plott|
00000f20  69 6e 67 2c 20 73 6f 20  74 68 65 20 63 65 6c 6c  |ing, so the cell|
00000f30  73 0a 64 6f 6e 27 74 20  6c 6f 6f 6b 20 73 74 72  |s.don't look str|
00000f40  65 74 63 68 65 64 2e 0a  0a 54 68 65 20 73 70 65  |etched...The spe|
00000f50  65 64 2d 63 72 69 74 69  63 61 6c 20 75 70 64 61  |ed-critical upda|
00000f60  74 65 20 72 6f 75 74 69  6e 65 20 69 73 20 77 72  |te routine is wr|
00000f70  69 74 74 65 6e 20 69 6e  20 41 73 73 65 6d 62 6c  |itten in Assembl|
00000f80  65 72 2c 20 61 6e 64 20  69 73 20 63 75 73 74 6f  |er, and is custo|
00000f90  6d 2d 0a 72 65 61 73 73  65 6d 62 6c 65 64 20 65  |m-.reassembled e|
00000fa0  76 65 72 79 20 74 69 6d  65 20 74 68 65 20 73 65  |very time the se|
00000fb0  74 74 69 6e 67 73 20 61  72 65 20 63 68 61 6e 67  |ttings are chang|
00000fc0  65 64 20 2d 20 74 68 69  73 20 66 72 65 65 73 20  |ed - this frees |
00000fd0  75 70 20 74 68 65 20 72  65 67 69 73 74 65 72 73  |up the registers|
00000fe0  0a 77 68 69 63 68 20 77  6f 75 6c 64 20 6f 74 68  |.which would oth|
00000ff0  65 72 77 69 73 65 20 62  65 20 6e 65 65 64 65 64  |erwise be needed|
00001000  20 74 6f 20 68 6f 6c 64  20 74 68 69 6e 67 73 20  | to hold things |
00001010  6c 69 6b 65 20 63 6f 6e  73 74 61 6e 74 73 20 61  |like constants a|
00001020  6e 64 20 67 72 69 64 20  73 69 7a 65 2e 0a 54 68  |nd grid size..Th|
00001030  65 20 67 72 69 64 20 69  73 20 73 74 6f 72 65 64  |e grid is stored|
00001040  20 69 6e 20 74 77 6f 20  32 35 36 2d 63 6f 6c 6f  | in two 256-colo|
00001050  75 72 20 73 70 72 69 74  65 73 2c 20 77 68 69 63  |ur sprites, whic|
00001060  68 20 61 72 65 20 65 61  73 79 20 74 6f 20 61 63  |h are easy to ac|
00001070  63 65 73 73 20 73 69 6e  63 65 0a 74 68 65 79 27  |cess since.they'|
00001080  72 65 20 6f 6e 65 20 62  79 74 65 20 70 65 72 20  |re one byte per |
00001090  70 69 78 65 6c 2e 20 28  54 77 6f 20 61 72 65 20  |pixel. (Two are |
000010a0  72 65 71 75 69 72 65 64  20 62 65 63 61 75 73 65  |required because|
000010b0  20 79 6f 75 20 64 6f 6e  27 74 20 77 61 6e 74 20  | you don't want |
000010c0  74 6f 20 73 74 61 72 74  0a 6f 76 65 72 77 72 69  |to start.overwri|
000010d0  74 69 6e 67 20 74 68 65  20 6f 6c 64 20 67 65 6e  |ting the old gen|
000010e0  65 72 61 74 69 6f 6e 20  62 65 66 6f 72 65 20 79  |eration before y|
000010f0  6f 75 27 76 65 20 66 69  6e 69 73 68 65 64 20 72  |ou've finished r|
00001100  65 61 64 69 6e 67 20 69  74 29 2e 20 4f 6e 65 20  |eading it). One |
00001110  6f 72 20 74 77 6f 0a 6d  69 6c 64 6c 79 20 63 75  |or two.mildly cu|
00001120  6e 6e 69 6e 67 20 74 65  63 68 6e 69 71 75 65 73  |nning techniques|
00001130  20 61 72 65 20 75 73 65  64 20 66 6f 72 20 73 70  | are used for sp|
00001140  65 65 64 2c 20 62 75 74  20 69 74 27 73 20 66 61  |eed, but it's fa|
00001150  69 72 6c 79 20 73 74 72  61 69 67 68 74 66 6f 72  |irly straightfor|
00001160  77 61 72 64 0a 72 65 61  6c 6c 79 2e 2e 2e 0a 0a  |ward.really.....|
00001170  49 6e 74 65 72 65 73 74  69 6e 67 20 72 65 73 75  |Interesting resu|
00001180  6c 74 73 20 63 61 6e 20  62 65 20 70 72 6f 64 75  |lts can be produ|
00001190  63 64 20 77 69 74 68 20  61 20 76 6f 6e 20 4e 65  |cd with a von Ne|
000011a0  75 6d 61 6e 6e 20 6e 65  69 67 68 62 6f 75 72 68  |umann neighbourh|
000011b0  6f 6f 64 2c 20 6e 3d 31  30 30 2c 0a 6b 31 3d 32  |ood, n=100,.k1=2|
000011c0  2c 20 6b 32 3d 33 2c 20  67 3d 31 38 20 6f 72 20  |, k2=3, g=18 or |
000011d0  74 68 65 72 65 61 62 6f  75 74 73 2e 20 41 70 70  |thereabouts. App|
000011e0  61 72 65 6e 74 6c 79 20  69 74 20 6c 6f 6f 6b 73  |arently it looks|
000011f0  20 61 20 62 69 74 20 6c  69 6b 65 20 63 65 72 74  | a bit like cert|
00001200  61 69 6e 0a 6f 73 63 69  6c 6c 61 74 69 6e 67 20  |ain.oscillating |
00001210  63 68 65 6d 69 63 61 6c  20 72 65 61 63 74 69 6f  |chemical reactio|
00001220  6e 73 2e 2e 2e 0a 0a 0a  43 4f 4e 54 41 43 54 5f  |ns......CONTACT_|
00001230  5f 5f 5f 5f 5f 5f 5f 5f  5f 5f 5f 5f 5f 5f 5f 5f  |________________|
*
00001270  5f 5f 5f 5f 5f 0a 0a 70  6f 6e 74 75 73 40 61 72  |_____..pontus@ar|
00001280  63 61 64 65 2e 64 65 6d  6f 6e 2e 63 6f 2e 75 6b  |cade.demon.co.uk|
00001290  2c 20 6f 72 20 39 20 4d  6f 6e 6d 6f 75 74 68 20  |, or 9 Monmouth |
000012a0  52 6f 61 64 2c 20 4f 78  66 6f 72 64 20 4f 58 31  |Road, Oxford OX1|
000012b0  20 34 54 44 2c 20 45 6e  67 6c 61 6e 64 0a 0a 48  | 4TD, England..H|
000012c0  61 70 70 69 6e 67 20 68  6f 64 67 69 6e 67 2e 2e  |apping hodging..|
000012d0  2e 0a 0a 50 6f 6e 74 0a                           |...Pont.|
000012d8