even an array doesn't make it faster...

src/grid.go

@@ -19,12 +19,15 @@ type Neighbor struct {
 	X, Y int
 }
 
+const max int = 2250000
+
 type Grid struct {
-	Data          []uint8
-	NeighborCount []int
-	Neighbors     [][]Neighbor
+	Data          [max]uint8
+	NeighborCount [max]int
+	Neighbors     [max][]Neighbor
 	Empty         bool
 	Config        *Config
+	Counter       func(x, y int) uint8
 }
 
 // Create new empty grid and allocate Data according to provided dimensions
@@ -34,28 +37,34 @@ func NewGrid(config *Config) *Grid {
 		STRIDE = config.Width
 	}
 
-	size := STRIDE * STRIDE
+	//size := STRIDE * STRIDE
 
 	grid := &Grid{
-		Data:          make([]uint8, size),
-		NeighborCount: make([]int, size),
-		Neighbors:     make([][]Neighbor, size),
-		Empty:         config.Empty,
-		Config:        config,
+		//Data:          make([]uint8, size),
+		//NeighborCount: make([]int, size),
+		//Neighbors:     make([][]Neighbor, size),
+		Empty:  config.Empty,
+		Config: config,
 	}
 
 	// first setup the cells
-	for y := 0; y < config.Height; y++ {
-		for x := 0; x < config.Width; x++ {
-			grid.Data[y+STRIDE*x] = 0
-		}
-	}
+	// for y := 0; y < config.Height; y++ {
+	// 	for x := 0; x < config.Width; x++ {
+	// 		grid.Data[y+STRIDE*x] = 0
+	// 	}
+	// }
 
 	// in a second pass, collect positions to the neighbors of each cell
-	for y := 0; y < config.Height; y++ {
-		for x := 0; x < config.Width; x++ {
-			grid.SetupNeighbors(x, y)
-		}
+	// for y := 0; y < config.Height; y++ {
+	// 	for x := 0; x < config.Width; x++ {
+	// 		grid.SetupNeighbors(x, y)
+	// 	}
+	// }
+
+	if grid.Config.Wrap {
+		grid.Counter = grid.CountNeighborsWrap
+	} else {
+		grid.Counter = grid.CountNeighbors
 	}
 
 	return grid
@@ -101,8 +110,69 @@ func (grid *Grid) SetupNeighbors(x, y int) {
 	grid.Neighbors[y+STRIDE*x] = neighbors
 }
 
-// count the living neighbors of a cell
+func (grid *Grid) CountNeighborsWrap(x, y int) uint8 {
+	var sum uint8
+	var col, row int
+
+	width := grid.Config.Width
+	height := grid.Config.Height
+
+	for nbgX := -1; nbgX < 2; nbgX++ {
+		for nbgY := -1; nbgY < 2; nbgY++ {
+
+			// In wrap mode we look at all the 8 neighbors surrounding us.
+			// In case we are on an edge we'll look at the neighbor on the
+			//  other side  of the  grid, thus  wrapping lookahead  around
+			// using the mod() function.
+			col = (x + nbgX + width) % width
+			row = (y + nbgY + height) % height
+
+			p := row + STRIDE*col
+			sum += grid.Data[p]
+		}
+	}
+
+	// don't count ourselfes though
+	sum -= grid.Data[y+STRIDE*x]
+
+	return sum
+}
+
 func (grid *Grid) CountNeighbors(x, y int) uint8 {
+	var sum uint8
+	var val uint8
+
+	width := grid.Config.Width
+	height := grid.Config.Height
+
+	for nbgX := -1; nbgX < 2; nbgX++ {
+		for nbgY := -1; nbgY < 2; nbgY++ {
+			var col, row int
+
+			xnbgX := x + nbgX
+			ynbgY := y + nbgY
+
+			// In traditional grid mode the edges are deadly
+			if xnbgX < 0 || xnbgX >= width || ynbgY < 0 || ynbgY >= height {
+				continue
+			}
+			col = xnbgX
+			row = ynbgY
+
+			p := row + STRIDE*col
+			val = grid.Data[p]
+			sum += val // this uses 18% of the whole running time!
+		}
+	}
+
+	// don't count ourselfes though
+	sum -= grid.Data[y+STRIDE*x]
+
+	return sum
+}
+
+// count the living neighbors of a cell
+func (grid *Grid) _CountNeighbors(x, y int) uint8 {
 	var count uint8
 
 	pos := y + STRIDE*x

src/play.go

@@ -167,7 +167,7 @@ func (scene *ScenePlay) UpdateCells() {
 
 			for x := 0; x < width; x++ {
 				state := scene.Grids[scene.Index].Data[y+STRIDE*x] // 0|1 == dead or alive
-				neighbors := scene.Grids[scene.Index].CountNeighbors(x, y)
+				neighbors := scene.Grids[scene.Index].Counter(x, y)
 
 				// actually apply the current rules
 				nextstate := scene.RuleCheckFunc(state, neighbors)