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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sync_test
import (
"runtime"
. "sync"
"sync/atomic"
"testing"
)
type one int
func (o *one) Increment() {
*o++
}
func run(once *Once, o *one, c chan bool) {
once.Do(func() { o.Increment() })
c <- true
}
func TestOnce(t *testing.T) {
o := new(one)
once := new(Once)
c := make(chan bool)
const N = 10
for i := 0; i < N; i++ {
go run(once, o, c)
}
for i := 0; i < N; i++ {
<-c
}
if *o != 1 {
t.Errorf("once failed: %d is not 1", *o)
}
}
func BenchmarkOnce(b *testing.B) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
var once Once
f := func() {}
c := make(chan bool, procs)
for p := 0; p < procs; p++ {
go func() {
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
once.Do(f)
}
}
c <- true
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
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