该问题涉及以下代码:
package main
import "fmt"
func main() {
var counters = map[int]int{}
for i := 0; i < 5; i++ {
go func(counters map[int]int, th int) {
for j := 0; j < 5; j++ {
counters[th*10+j]++
}
}(counters, i)
}
fmt.Scanln()
fmt.Println("counters result", counters)
}
这是当我用go run -race race.go
运行此代码时得到的输出>
$ go run -race race.go ================== WARNING: DATA RACE Read at 0x00c000092150 by goroutine 8: runtime.mapaccess1_fast64() /usr/lib/go-1.13/src/runtime/map_fast64.go:12 +0x0 main.main.func1() /tmp/race.go:10 +0x6b Previous write at 0x00c000092150 by goroutine 7: runtime.mapassign_fast64() /usr/lib/go-1.13/src/runtime/map_fast64.go:92 +0x0 main.main.func1() /tmp/race.go:10 +0xaf Goroutine 8 (running) created at: main.main() /tmp/race.go:8 +0x67 Goroutine 7 (finished) created at: main.main() /tmp/race.go:8 +0x67 ================== ================== WARNING: DATA RACE Read at 0x00c0000aa188 by main goroutine: reflect.typedmemmove() /usr/lib/go-1.13/src/runtime/mbarrier.go:177 +0x0 reflect.copyVal() /usr/lib/go-1.13/src/reflect/value.go:1297 +0x7b reflect.(*MapIter).Value() /usr/lib/go-1.13/src/reflect/value.go:1251 +0x15e internal/fmtsort.Sort() /usr/lib/go-1.13/src/internal/fmtsort/sort.go:61 +0x259 fmt.(*pp).printValue() /usr/lib/go-1.13/src/fmt/print.go:773 +0x146f fmt.(*pp).printArg() /usr/lib/go-1.13/src/fmt/print.go:716 +0x2ee fmt.(*pp).doPrintln() /usr/lib/go-1.13/src/fmt/print.go:1173 +0xad fmt.Fprintln() /usr/lib/go-1.13/src/fmt/print.go:264 +0x65 main.main() /usr/lib/go-1.13/src/fmt/print.go:274 +0x13c Previous write at 0x00c0000aa188 by goroutine 10: main.main.func1() /tmp/race.go:10 +0xc4 Goroutine 10 (finished) created at: main.main() /tmp/race.go:8 +0x67 ================== counters result map[0:1 1:1 2:1 3:1 4:1 10:1 11:1 12:1 13:1 14:1 20:1 21:1 22:1 23:1 24:1 30:1 31:1 32:1 33:1 34:1 40:1 41:1 42:1 43:1 44:1] Found 2 data race(s) exit status 66
这是我不明白的地方。为什么根本有比赛条件?我们不是只通过一遍例程就可以读取/写入值吗?例如,例程0将仅修改
counter[0]
至counters[4]
中的值,例程1将仅修改counters[10]
至counters[14]
中的值,例程2将仅修改counters[20]
至counters[24]
中的值,依此类推。我没有在这里看到比赛条件。感觉就像我错过了什么。有人可以对此有所启发吗?
仅供参考,我是新手。如果您能简化解释(如果可能的话),我将不胜感激。
该问题涉及以下代码:包main import“ fmt” func main(){var counters = map [int] int {} for i:= 0;我<5; i ++ {go func(counters map [int] int,th int){...
对于数组(或切片)来说确实如此,但是映射是一个复杂的数据结构,除其他外,它具有以下属性: