# Forest fire model

# https://en.wikipedia.org/wiki/Forest-fire_model

​

# Defaults, can be assert()ed to different values

pIgnition is 1. # P(Ignition) * 10000

pGrowth is 100. # P(Tree grows) * 10000

​

# Some math

#builtin INT_PLUS plus

dir 0 1. dir 0 -1. dir 1 0. dir -1 0.

​

# Default: no changes

next X Y is? State :- current X Y is State.

​

# A burning cell turns into an empty cell

next X Y is empty :-

   current X Y is fire.

​

# A tree will burn if a neighbor is burining

next X Y is fire :-

   dir DX DY, 

   current X Y is tree,

   current (plus X DX) (plus Y DY) is fire.

​

# A tree ignites with probability pIgnition

next X Y is fire :-

   current X Y is tree,

   rand X Y is V, V < pIgnition.

​

# A tree grows in an empty cell with probability pGrowth

next X Y is tree :-

   current X Y is empty,

   rand X Y is V, V < pGrowth.

`);

​

const GRID_W = 100;

const GRID_H = 125;

const CELL_SIZE = 10;

const INIT_FIRE_X = Math.floor(Math.random() * GRID_W);

const INIT_FIRE_Y = Math.floor(Math.random() * GRID_H);

const INIT_TREE_P = 0.5;

​

let cells = [];

for (let x = 0; x < GRID_W; x++) {

  for (let y = 0; y < GRID_H; y++) {

    const state = { name: "empty" };

    if (x === INIT_FIRE_X && y === INIT_FIRE_Y) {

      state.name = 'fire';

    } else if (Math.random() < INIT_TREE_P) {

      state.name = 'tree';

    }

    cells.push({ name: 'current', args: [x,y], value: state })

  }

}

​

function coordToFact([x, y, state]) {

  return { name: "current", args: [x,y], value: state };

}

​

​

function setup() {

  createCanvas(GRID_W * CELL_SIZE, GRID_H * CELL_SIZE);

}

​

function draw() {

  background(0);

  for (const { args: [x,y], value: {name: state} } of cells ) {

    if (state === 'tree') {

      fill("#0000FF");

      rect(x*CELL_SIZE, y*CELL_SIZE, CELL_SIZE, CELL_SIZE);

    } else if (state === 'fire') {

      fill("#FF0000");

      rect(x*CELL_SIZE, y*CELL_SIZE, CELL_SIZE, CELL_SIZE); 

    }

  }

​

  const dusa = new Dusa(FIRE);

  dusa.assert(...cells);

  dusa.assert(...cells.map(({args}) => ({name: "rand", args, value: Math.floor(Math.random() * 10000)})));

  cells = [...dusa.solution.lookup("next")].map(coordToFact);

}