HI all,
So I figured Conways game of life would be a good exercise to get my feet
wet with go. Specifically i wanted to make the calculation of the next
board state to be concurrent.
I started a separate goroutine for each cell and then used a pair of
channels to synchronize updating to the next state and displaying the
board.
Would love to hear opinions on this approach? are their better or more
effective ways to do the same thing?
Thanks in advance,
CR
package main
import (
"fmt"
"math/rand"
"time"
)
type Cell struct {
x int
y int
currentState bool
nw *Cell
n *Cell
ne *Cell
e *Cell
se *Cell
s *Cell
sw *Cell
w *Cell
}
func (c *Cell) cell(runChan chan string, doneChan chan string) {
for {
// wait until we're allowed to proceed
_ = <-runChan
// count the number of neighbours
var i int = 0
if c.nw.currentState {
i++
}
if c.n.currentState {
i++
}
if c.ne.currentState {
i++
}
if c.e.currentState {
i++
}
if c.se.currentState {
i++
}
if c.s.currentState {
i++
}
if c.sw.currentState {
i++
}
if c.w.currentState {
i++
}
// Any live cell with fewer than two live neighbours dies, as if
caused by under-population.
// Any live cell with two or three live neighbours lives on to the
next generation.
// Any live cell with more than three live neighbours dies, as if
by over-population.
// Any dead cell with exactly three live neighbours becomes a live
cell, as if by reproduction.
nextState := c.currentState
if c.currentState == true {
if i < 2 {
nextState = false
} else if i == 2 {
nextState = true
} else if i == 3 {
nextState = true
} else if i > 3 {
nextState = false
}
} else {
if i == 3 {
nextState = true
}
}
//fmt.Println("calc for ", c.x, c.y, c.currentState, nextState, i)
// report that we're finished the calc
doneChan <- "done"
// wait for permission to continue
_ = <-runChan
c.currentState = nextState
// report that we've done the transition
doneChan <- "done"
//fmt.Println("assign")
}
}
func ring(x int, size int) int {
// this corrects x to be in the range 0..size-1
if x < 0 {
return size + x
} else if x >= size {
return 0
} else {
return x
}
}
func main() {
const iterations = 10
const gridSize = 50
const numCells = gridSize * gridSize
r := rand.New(rand.NewSource(123))
var cells [numCells]Cell
// set up the cells
for y := 0; y < gridSize; y++ {
for x := 0; x < gridSize; x++ {
cells[x+gridSize*y].x = x
cells[x+gridSize*y].y = y
cells[x*gridSize+y].currentState = r.Intn(4) == 0
cells[x+gridSize*y].nw = &cells[ring(x-1, gridSize)+gridSize*
ring(y-1, gridSize)]
cells[x+gridSize*y].n = &cells[ring(x, gridSize)+gridSize*ring(y
-1, gridSize)]
cells[x+gridSize*y].ne = &cells[ring(x+1, gridSize)+gridSize*
ring(y-1, gridSize)]
cells[x+gridSize*y].e = &cells[ring(x+1, gridSize)+gridSize*ring
(y, gridSize)]
cells[x+gridSize*y].se = &cells[ring(x+1, gridSize)+gridSize*
ring(y+1, gridSize)]
cells[x+gridSize*y].s = &cells[ring(x, gridSize)+gridSize*ring(y
+1, gridSize)]
cells[x+gridSize*y].sw = &cells[ring(x-1, gridSize)+gridSize*
ring(y+1, gridSize)]
cells[x+gridSize*y].w = &cells[ring(x-1, gridSize)+gridSize*ring
(y, gridSize)]
}
}
calcChan := make(chan string)
readyChan := make(chan string)
// start a goroutine for each cell
for i := 0; i < numCells; i++ {
go cells[i].cell(calcChan, readyChan)
}
for x := 0; x < iterations; x++ {
// display board
for y := 0; y < gridSize; y++ {
for x := 0; x < gridSize; x++ {
if cells[x+gridSize*y].currentState {
fmt.Print("X")
} else {
fmt.Print(" ")
}
}
fmt.Println("")
}
fmt.Println("start the calucation")
for i := 0; i < numCells; i++ {
calcChan <- ""
}
fmt.Println("waiting for calculations to complate")
for i := 0; i < numCells; i++ {
_ = <-readyChan
}
fmt.Println("start the transition")
for i := 0; i < numCells; i++ {
calcChan <- ""
}
fmt.Println("waiting for transition to complate")
for i := 0; i < numCells; i++ {
_ = <-readyChan
}
fmt.Println("calculations done. ")
}
time.Sleep(2000)
fmt.Println("Done")
}
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