Add -cpuprofile option (#14)

example/main.go

@@ -1,18 +1,36 @@
 package main
 
 import (
+	"flag"
 	"github.com/hajimehoshi/ebiten/example/blocks"
 	"github.com/hajimehoshi/ebiten/ui"
 	"github.com/hajimehoshi/ebiten/ui/glfw"
+	"log"
+	"os"
 	"runtime"
+	"runtime/pprof"
 )
 
 func init() {
 	runtime.LockOSThread()
 }
 
+var cpuProfile = flag.String("cpuprofile", "", "write cpu profile to file")
+
 func main() {
+	flag.Parse()
+	if *cpuProfile != "" {
+		f, err := os.Create(*cpuProfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		pprof.StartCPUProfile(f)
+		defer pprof.StopCPUProfile()
+	}
+
 	u := new(glfw.UI)
 	game := blocks.NewGame()
-	ui.Run(u, game, blocks.ScreenWidth, blocks.ScreenHeight, 2, "Ebiten Demo", 60)
+	if err := ui.Run(u, game, blocks.ScreenWidth, blocks.ScreenHeight, 2, "Ebiten Demo", 60); err != nil {
+		log.Fatal(err)
+	}
 }

readme.md

@@ -26,6 +26,15 @@ changed easily.
 :; go run main.go
 ```
 
+### How to benchmark the example
+
+```
+:; cd $GOHOME/src/github.com/hajimehoshi/ebiten/example
+:; go build -o=example main.go
+:; ./example -cpuprofile=cpu.out
+:; go tool pprof ./example cpu.out
+```
+
 ## License
 
 Copyright 2014 Hajime Hoshi