我閱讀了Go的并發模型，還看到了并發性和并行性之間的區別。為了測試并行執行，我編寫了以下程序。package mainimport ( "fmt" "runtime" "time")const count = 1e8var buffer [count]intfunc main() { fmt.Println("GOMAXPROCS: ", runtime.GOMAXPROCS(0)) // Initialise with dummy value for i := 0; i < count; i++ { buffer[i] = 3 } // Sequential operation now := time.Now() worker(0, count-1) fmt.Println("sequential operation: ", time.Since(now)) // Attempt to parallelize ch := make(chan int, 1) now = time.Now() go func() { worker(0, (count/2)-1) ch <- 1 }() worker(count/2, count-1) <-ch fmt.Println("parallel operation: ", time.Since(now))}func worker(start int, end int) { for i := start; i <= end; i++ { task(i) }}func task(index int) { buffer[index] = 2 * buffer[index]}但問題是：結果不是很令人愉快。GOMAXPROCS: 8sequential operation: 206.85msparallel operation: 169.028ms使用戈魯丁確實可以加快速度，但還不夠。我預計它的速度會接近兩倍。我的代碼和/或理解有什么問題？我怎樣才能接近兩倍的速度？
1 回答
倚天杖
TA貢獻1828條經驗 獲得超3個贊
并行化功能強大，但很難在如此小的計算負載下看到。下面是一些結果差異較大的示例代碼：
package main
import (
"fmt"
"math"
"runtime"
"time"
)
func calctest(nCPU int) {
fmt.Println("Routines:", nCPU)
ch := make(chan float64, nCPU)
startTime := time.Now()
a := 0.0
b := 1.0
n := 100000.0
deltax := (b - a) / n
stepPerCPU := n / float64(nCPU)
for start := 0.0; start < n; {
stop := start + stepPerCPU
go f(start, stop, a, deltax, ch)
start = stop
}
integral := 0.0
for i := 0; i < nCPU; i++ {
integral += <-ch
}
fmt.Println(time.Now().Sub(startTime))
fmt.Println(deltax * integral)
}
func f(start, stop, a, deltax float64, ch chan float64) {
result := 0.0
for i := start; i < stop; i++ {
result += math.Sqrt(a + deltax*(i+0.5))
}
ch <- result
}
func main() {
nCPU := runtime.NumCPU()
calctest(nCPU)
fmt.Println("")
calctest(1)
}
這是我得到的結果：
Routines: 8
853.181μs
Routines: 1
2.031358ms
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