| // +build ignore,OMIT | |
| package main | |
| import ( | |
| "runtime" | |
| "sync" | |
| ) | |
| func main() { | |
| runtime.GOMAXPROCS(runtime.NumCPU()) | |
| count(10000) // what if we have 1, 2, 25? | |
| } | |
| func count(n int) { | |
| var wg sync.WaitGroup | |
| wg.Add(n) | |
| m := map[int]int{} | |
| var mu sync.Mutex // HL | |
| for i := 1; i <= n; i++ { | |
| go func(i int) { | |
| for j := 0; j < i; j++ { | |
| mu.Lock() // HL | |
| m[i]++ | |
| mu.Unlock() // HL | |
| } | |
| wg.Done() | |
| }(i) | |
| } | |
| wg.Wait() | |
| } |