conway_typedarray.js

var COLS = 177;
var ROWS = 60;

var update_ghost = function(grid, ghost_grid) {
	/*
	A virtual grid that includes wrapped edges, so that we don't have to
	do funky modulo arithmetic.
	*/

	var n, x, y;

	/* Copy bottom of grid to top of ghost_grid */
	for(n=0; n < COLS; n++) {
		ghost_grid.set(0, n+1, grid.get(ROWS-1, n));
	}

	/* Copy top of grid to bottom of ghost_grid */
	for(n=0; n < COLS; n++) {
		ghost_grid.set(ROWS+2-1, n+1, grid.get(0, n));
	}

	/* Copy the rest of grid to ghost_grid */
	for(y=0; y < ROWS; y++) {
		for(x=0; x < COLS; x++) {
			ghost_grid.set(y+1, x+1, grid.get(y, x));
		}
	}

	/* Wrap ghost_grid left and right columns */
	for(y=0; y < ROWS+2; y++) {
		ghost_grid.set(y, 0, ghost_grid.get(y, COLS+2-2));
		ghost_grid.set(y, COLS+2-1, ghost_grid.get(y, 1));
	}
}

var count_neighbors = function(x, y, ghost_grid) {
	return (
		ghost_grid.get((y-1)+1, (x-1)+1) + ghost_grid.get((y-1)+1, (x)+1) + ghost_grid.get((y-1)+1, (x+1)+1) +
		ghost_grid.get((y  )+1, (x-1)+1)                                  + ghost_grid.get((y  )+1, (x+1)+1) +
		ghost_grid.get((y+1)+1, (x-1)+1) + ghost_grid.get((y+1)+1, (x)+1) + ghost_grid.get((y+1)+1, (x+1)+1));
}

var out = new Buffer((COLS+1)*ROWS);
var pretty_print = function(grid) {
	var x, y;
	var out_i = 0;
	for(y=0; y <= ROWS-1; y++) {
		for(x=0; x <= COLS-1; x++) {
			if(grid.get(y, x) == 0) {
				out[out_i] = 32; // " "
				out_i += 1;
			} else {
				out[out_i] = 35; // "#"
				out_i += 1;
			}
		}
		out[out_i] = 10; // "\n"
		out_i += 1;
	}
	process.stdout.write(out);
}

var next_gen = function(grid, ghost_grid) {
	var neighbors, x, y;
	for(y=0; y < ROWS; y++) {
		for(x=0; x < COLS; x++) {
			neighbors = count_neighbors(x, y, ghost_grid);
			//printf("N %d, ", neighbors);
			if(neighbors < 2 || neighbors > 3) {
				grid.set(y, x, 0);
			} else if(neighbors == 3) {
				grid.set(y, x, 1);
			}
		}
	}
	update_ghost(grid, ghost_grid);
}

var make_grid = function(width, height) {
	var arr = Uint8Array(width * height);
	return {
		get: function(y, x) { return arr[y*COLS + x]; },
		set: function(y, x, val) { arr[y*COLS + x] = val; },
	}
}

var run_once = function() {
	var grid = make_grid(COLS, ROWS);
	var ghost_grid = make_grid(COLS + 2, ROWS + 2);
	var x;
	var y;

	/* Generate a random grid */
	for(y=0; y < ROWS; y++) {
		for(x=0; x < COLS; x++) {
			grid.set(y, x, Math.floor(Math.random() * 2));
		}
	}

	pretty_print(grid);
	update_ghost(grid, ghost_grid);

	var iterations = 50000;

	while(iterations--) {
		process.stdout.write("\n\n\n");
		pretty_print(grid);
		//nanosleep(&wait, NULL);

		next_gen(grid, ghost_grid);
	}
}

var main = function() {
	run_once();
	process.stderr.write("Warmed up.\n");
	var start = Date.now();
	run_once()
	var end = Date.now();
	process.stderr.write("Ran in " + (end - start) + "ms\n");
}

main();