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Golang array map, concurrency problem
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| package main | |
| import ( | |
| "fmt" | |
| "sync" | |
| "time" | |
| ) | |
| func Map[T1, T2 any](arr []T1, f func(item T1, index int) T2) []T2 { | |
| arrT2 := make([]T2, len(arr)) | |
| for i, t := range arr { | |
| t2 := f(t, i) | |
| arrT2[i] = t2 | |
| } | |
| return arrT2 | |
| } | |
| func MapConcurrent[T1, T2 any](arr []T1, f func(item T1, index int) T2) []T2 { | |
| var wg sync.WaitGroup | |
| wg.Add(len(arr)) | |
| arrT2 := make([]T2, len(arr)) | |
| for i, t := range arr { | |
| go func() { | |
| t2 := f(t, i) | |
| arrT2[i] = t2 | |
| wg.Done() | |
| }() | |
| } | |
| wg.Wait() | |
| return arrT2 | |
| } | |
| func MapConcurrentWorkerPool[T1, T2 any](arr []T1, f func(item T1, index int) T2) []T2 { | |
| arrT2 := make([]T2, len(arr)) | |
| const N_WORKERS = 10 | |
| type indexT1 struct { | |
| index int | |
| t1 T1 | |
| } | |
| type indexT2 struct { | |
| index int | |
| t2 T2 | |
| } | |
| inputs := make(chan indexT1, N_WORKERS) | |
| results := make(chan indexT2, N_WORKERS) | |
| var wg sync.WaitGroup | |
| wg.Add(N_WORKERS) | |
| worker := func() { | |
| for t1 := range inputs { | |
| t2 := f(t1.t1, t1.index) | |
| results <- indexT2{t1.index, t2} | |
| } | |
| wg.Done() | |
| } | |
| for range N_WORKERS { | |
| go worker() | |
| } | |
| go func() { | |
| wg.Wait() | |
| close(results) | |
| }() | |
| go func() { | |
| for i, t := range arr { | |
| inputs <- indexT1{i, t} | |
| } | |
| close(inputs) | |
| }() | |
| for t2 := range results { | |
| arrT2[t2.index] = t2.t2 | |
| } | |
| return arrT2 | |
| } | |
| type Number struct { | |
| a int | |
| } | |
| func main() { | |
| const n = 10000000 | |
| arr := make([]Number, 0, n) | |
| for i := range n { | |
| arr = append(arr, Number{i}) | |
| } | |
| returnInt := func(t Number, index int) int { | |
| return t.a | |
| } | |
| func() { | |
| defer timer("normal map")() | |
| Map(arr, returnInt) | |
| }() | |
| func() { | |
| defer timer("infinite goroutines map")() | |
| MapConcurrent(arr, returnInt) | |
| }() | |
| func() { | |
| defer timer("worker pool map")() | |
| MapConcurrentWorkerPool(arr, returnInt) | |
| }() | |
| } | |
| func timer(name string) func() { | |
| start := time.Now() | |
| return func() { | |
| fmt.Printf("%s took %v\n", name, time.Since(start)) | |
| } | |
| } |
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