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// Copyright 2017 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 semaphore_test
import (
"context"
"fmt"
"testing"
"golang.org/x/sync/semaphore"
)
// weighted is an interface matching a subset of *Weighted. It allows
// alternate implementations for testing and benchmarking.
type weighted interface {
Acquire(context.Context, int64) error
TryAcquire(int64) bool
Release(int64)
}
// semChan implements Weighted using a channel for
// comparing against the condition variable-based implementation.
type semChan chan struct{}
func newSemChan(n int64) semChan {
return semChan(make(chan struct{}, n))
}
func (s semChan) Acquire(_ context.Context, n int64) error {
for i := int64(0); i < n; i++ {
s <- struct{}{}
}
return nil
}
func (s semChan) TryAcquire(n int64) bool {
if int64(len(s))+n > int64(cap(s)) {
return false
}
for i := int64(0); i < n; i++ {
s <- struct{}{}
}
return true
}
func (s semChan) Release(n int64) {
for i := int64(0); i < n; i++ {
<-s
}
}
// acquireN calls Acquire(size) on sem N times and then calls Release(size) N times.
func acquireN(b *testing.B, sem weighted, size int64, N int) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
for j := 0; j < N; j++ {
sem.Acquire(context.Background(), size)
}
for j := 0; j < N; j++ {
sem.Release(size)
}
}
}
// tryAcquireN calls TryAcquire(size) on sem N times and then calls Release(size) N times.
func tryAcquireN(b *testing.B, sem weighted, size int64, N int) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
for j := 0; j < N; j++ {
if !sem.TryAcquire(size) {
b.Fatalf("TryAcquire(%v) = false, want true", size)
}
}
for j := 0; j < N; j++ {
sem.Release(size)
}
}
}
func BenchmarkNewSeq(b *testing.B) {
for _, cap := range []int64{1, 128} {
b.Run(fmt.Sprintf("Weighted-%d", cap), func(b *testing.B) {
for i := 0; i < b.N; i++ {
_ = semaphore.NewWeighted(cap)
}
})
b.Run(fmt.Sprintf("semChan-%d", cap), func(b *testing.B) {
for i := 0; i < b.N; i++ {
_ = newSemChan(cap)
}
})
}
}
func BenchmarkAcquireSeq(b *testing.B) {
for _, c := range []struct {
cap, size int64
N int
}{
{1, 1, 1},
{2, 1, 1},
{16, 1, 1},
{128, 1, 1},
{2, 2, 1},
{16, 2, 8},
{128, 2, 64},
{2, 1, 2},
{16, 8, 2},
{128, 64, 2},
} {
for _, w := range []struct {
name string
w weighted
}{
{"Weighted", semaphore.NewWeighted(c.cap)},
{"semChan", newSemChan(c.cap)},
} {
b.Run(fmt.Sprintf("%s-acquire-%d-%d-%d", w.name, c.cap, c.size, c.N), func(b *testing.B) {
acquireN(b, w.w, c.size, c.N)
})
b.Run(fmt.Sprintf("%s-tryAcquire-%d-%d-%d", w.name, c.cap, c.size, c.N), func(b *testing.B) {
tryAcquireN(b, w.w, c.size, c.N)
})
}
}
}
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