From: Siraaj Khandkar <siraaj@khandkar.net>
Date: Mon, 3 Sep 2012 06:21:26 +0000 (-0400)
Subject: Forest-fire model 001.
X-Git-Url: https://git.xandkar.net/?p=cellular-automata.git;a=commitdiff_plain;h=debaffddb210096a01c9965e0ca1611402ce1f05

Forest-fire model 001.
---

diff --git a/forest-fire/001/.gitignore b/forest-fire/001/.gitignore
new file mode 100644
index 0000000..a97bb19
--- /dev/null
+++ b/forest-fire/001/.gitignore
@@ -0,0 +1,4 @@
+bin/*
+*.o
+*.cmi
+*.cmx
diff --git a/forest-fire/001/Makefile b/forest-fire/001/Makefile
new file mode 100644
index 0000000..7da721b
--- /dev/null
+++ b/forest-fire/001/Makefile
@@ -0,0 +1,18 @@
+COMPILER="ocamlopt"
+OBJ_EXT="cmx"
+
+
+compile:
+	@mkdir -p bin
+	@ocamlfind $(COMPILER) -linkpkg -package unix \
+			-o bin/forest_fire \
+			   src/forest_fire.ml
+
+
+clean:
+	@rm -rf bin
+	@find src \
+		    -iname '*.o' \
+		-or -iname '*.cmi' \
+		-or -iname '*.$(OBJ_EXT)' \
+		| xargs rm
diff --git a/forest-fire/001/src/forest_fire.ml b/forest-fire/001/src/forest_fire.ml
new file mode 100644
index 0000000..98dad01
--- /dev/null
+++ b/forest-fire/001/src/forest_fire.ml
@@ -0,0 +1,180 @@
+open Printf
+
+
+(* ------------------------------------------------------------------------- *
+ * Constants
+ * ------------------------------------------------------------------------- *)
+let f = 0.01  (* Probability of spontaneous ignition *)
+let p = 1.0   (* Probability of spontaneous growth *)
+
+let default_x = 80
+let default_y = 25
+
+let char_empty   = ' '
+let char_tree    = 'T'
+let char_burning = '#'
+
+let ansi_color_tree    = "\027[0;32m"  (* Green *)
+let ansi_color_burning = "\027[1;31m"  (* Red *)
+let ansi_color_off     = "\027[0m"
+
+let ansi_code_clear = "\027[2J"    (* Clear screen *)
+let ansi_code_reset = "\027[1;1H"  (* Reset cursor position *)
+
+
+(* ------------------------------------------------------------------------- *
+ * Types
+ * ------------------------------------------------------------------------- *)
+type cell_state =
+  | Empty | Tree | Burning
+
+
+type direction =
+  | N | NE | E | SE | S | SW | W | NW
+
+
+type options =
+  { size : int * int
+  }
+
+
+(* ------------------------------------------------------------------------- *
+ * Utils
+ * ------------------------------------------------------------------------- *)
+
+(* Hack to sleep less than 1 sec *)
+let minisleep subsec =
+  ignore (Unix.select [] [] [] subsec)
+
+
+let term_clear () =
+  print_string ansi_code_clear
+
+
+let term_reset () =
+  print_string ansi_code_reset
+
+
+let get_opts argv =
+  let usage = ""
+
+  and x = ref default_x
+  and y = ref default_y in
+
+  let speclist = Arg.align [
+    ("-x", Arg.Set_int x, " X.");
+    ("-y", Arg.Set_int y, " Y.");
+  ] in
+
+  Arg.parse speclist (fun _ -> ()) usage;
+
+  { size = !x, !y
+  }
+
+
+(* ------------------------------------------------------------------------- *
+ * Core
+ * ------------------------------------------------------------------------- *)
+let directions =
+  [N; NE; E; SE; S; SW; W; NW]
+
+
+let offset_of_direction = function
+  (* Direction -> x, y *)
+  | N  ->  0, -1
+  | NE ->  1, -1
+  | E  ->  1,  0
+  | SE ->  1,  1
+  | S  ->  0,  1
+  | SW -> -1,  1
+  | W  -> -1,  0
+  | NW -> -1, -1
+
+
+let offsets =
+  List.map (offset_of_direction) directions
+
+
+let is_probable = function
+  | probability when (Random.float 1.0) <= probability -> true
+  | _ -> false
+
+
+let init_cell_state = function
+  | () when is_probable p -> Tree
+  | ()                    -> Empty
+
+
+let init_forest (x, y) =
+  Array.map (Array.map (init_cell_state)) (Array.make_matrix y x ())
+
+
+let string_of_state = function
+  | Empty   -> sprintf "%c" char_empty
+  | Tree    -> sprintf "%s%c%s" ansi_color_tree char_tree ansi_color_off
+  | Burning -> sprintf "%s%c%s" ansi_color_burning char_burning ansi_color_off
+
+
+let new_state = function
+  | Burning, _                                            -> Empty
+  | Tree,    0                 when is_probable f         -> Burning
+  | Tree,    neighbors_burning when neighbors_burning > 0 -> Burning
+  | Empty,   _                 when is_probable p         -> Tree
+  | state,   _                                            -> state
+
+
+let print_forest forest =
+  Array.iter
+  (
+    fun row ->
+      Array.iter
+      (
+        fun state ->
+          print_string (string_of_state state)
+      )
+      row;
+      print_newline ()
+  )
+  forest
+
+
+let is_onside width height (x, y) =
+  x >= 0 && y >= 0 && x < width && y < height
+
+
+let next_generation forest (width, height) =
+  Array.mapi
+  (
+    fun iy row ->
+      Array.mapi
+      (
+        fun ix state ->
+          let neighbors = List.map (fun (ox, oy) -> ox + ix, oy + iy) offsets in
+          let neighbors = List.filter (is_onside width height) neighbors in
+          let neighbor_states = List.map (fun (x, y) -> forest.(y).(x)) neighbors in
+          let burning_states = List.filter (fun s -> s == Burning) neighbor_states in
+          new_state (state, (List.length burning_states))
+      )
+      row
+  )
+  forest
+
+
+let rec burn forest size =
+  term_reset ();
+  print_forest forest;
+  minisleep 0.1;
+  burn (next_generation forest size) size
+
+
+let main argv =
+  Random.self_init ();
+
+  let opts = get_opts argv in
+  let forest = init_forest opts.size in
+
+  term_clear ();
+  burn forest opts.size
+
+
+let () = main Sys.argv