Hi,
I'm trying to understand output of the "go tool trace". I'm using
runtime.LockOSThread, however the output of the trace tool shows goroutines
moving between procs (which I *think* are OS threads). What am I missing?
Code:
package main
import (
"fmt"
"os"
"runtime"
"runtime/trace"
"time"
)
func sqrt(val float64) (float64, error) {
if val < 0.0 {
return 0.0, fmt.Errorf("sqrt of negative number")
}
if val == 0.0 {
return 0.0, nil // shortcut
}
guess, epsilon := 1.0, 0.00001
for i := 0; i < 10000; i++ {
diff := guess*guess - val
if diff < 0 {
diff = -diff
}
if diff <= epsilon {
return guess, nil
}
guess = (val/guess + guess) / 2.0
}
return 0.0, fmt.Errorf("can't find sqrt of %f", val)
}
func worker(id int) {
runtime.LockOSThread()
i := float64(0)
for {
for n := 0; n < 1000000; n++ {
i += 13.2
_, err := sqrt(i)
if err != nil {
panic(err)
}
}
runtime.Gosched()
}
}
func main() {
out, err := os.Create("trace.out")
if err != nil {
panic(err)
}
defer out.Close()
if err := trace.Start(out); err != nil {
panic(err)
}
defer trace.Stop()
for i := 0; i < runtime.NumCPU(); i++ {
go worker(i)
}
time.Sleep(3 * time.Second)
}
What I see in trace:
[image: trace-out.png]
Thanks,
Miki
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