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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 testing
import (
"flag"
"fmt"
"os"
"runtime"
"time"
)
var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
// An internal type but exported because it is cross-package; part of the implementation
// of gotest.
type InternalBenchmark struct {
Name string
F func(b *B)
}
// B is a type passed to Benchmark functions to manage benchmark
// timing and to specify the number of iterations to run.
type B struct {
N int
benchmark InternalBenchmark
ns int64
bytes int64
start int64
}
// StartTimer starts timing a test. This function is called automatically
// before a benchmark starts, but it can also used to resume timing after
// a call to StopTimer.
func (b *B) StartTimer() { b.start = time.Nanoseconds() }
// StopTimer stops timing a test. This can be used to pause the timer
// while performing complex initialization that you don't
// want to measure.
func (b *B) StopTimer() {
if b.start > 0 {
b.ns += time.Nanoseconds() - b.start
}
b.start = 0
}
// ResetTimer stops the timer and sets the elapsed benchmark time to zero.
func (b *B) ResetTimer() {
b.start = 0
b.ns = 0
}
// SetBytes records the number of bytes processed in a single operation.
// If this is called, the benchmark will report ns/op and MB/s.
func (b *B) SetBytes(n int64) { b.bytes = n }
func (b *B) nsPerOp() int64 {
if b.N <= 0 {
return 0
}
return b.ns / int64(b.N)
}
// runN runs a single benchmark for the specified number of iterations.
func (b *B) runN(n int) {
// Try to get a comparable environment for each run
// by clearing garbage from previous runs.
runtime.GC()
b.N = n
b.ResetTimer()
b.StartTimer()
b.benchmark.F(b)
b.StopTimer()
}
func min(x, y int) int {
if x > y {
return y
}
return x
}
func max(x, y int) int {
if x < y {
return y
}
return x
}
// roundDown10 rounds a number down to the nearest power of 10.
func roundDown10(n int) int {
var tens = 0
// tens = floor(log_10(n))
for n > 10 {
n = n / 10
tens++
}
// result = 10^tens
result := 1
for i := 0; i < tens; i++ {
result *= 10
}
return result
}
// roundUp rounds x up to a number of the form [1eX, 2eX, 5eX].
func roundUp(n int) int {
base := roundDown10(n)
if n < (2 * base) {
return 2 * base
}
if n < (5 * base) {
return 5 * base
}
return 10 * base
}
// run times the benchmark function. It gradually increases the number
// of benchmark iterations until the benchmark runs for a second in order
// to get a reasonable measurement. It prints timing information in this form
// testing.BenchmarkHello 100000 19 ns/op
func (b *B) run() BenchmarkResult {
// Run the benchmark for a single iteration in case it's expensive.
n := 1
b.runN(n)
// Run the benchmark for at least a second.
for b.ns < 1e9 && n < 1e9 {
last := n
// Predict iterations/sec.
if b.nsPerOp() == 0 {
n = 1e9
} else {
n = 1e9 / int(b.nsPerOp())
}
// Run more iterations than we think we'll need for a second (1.5x).
// Don't grow too fast in case we had timing errors previously.
// Be sure to run at least one more than last time.
n = max(min(n+n/2, 100*last), last+1)
// Round up to something easy to read.
n = roundUp(n)
b.runN(n)
}
return BenchmarkResult{b.N, b.ns, b.bytes}
}
// The results of a benchmark run.
type BenchmarkResult struct {
N int // The number of iterations.
Ns int64 // The total time taken.
Bytes int64 // The total number of bytes processed.
}
func (r BenchmarkResult) NsPerOp() int64 {
if r.N <= 0 {
return 0
}
return r.Ns / int64(r.N)
}
func (r BenchmarkResult) String() string {
ns := r.NsPerOp()
mb := ""
if ns > 0 && r.Bytes > 0 {
mb = fmt.Sprintf("\t%7.2f MB/s", (float64(r.Bytes)/1e6)/(float64(ns)/1e9))
}
return fmt.Sprintf("%8d\t%10d ns/op%s", r.N, ns, mb)
}
// An internal function but exported because it is cross-package; part of the implementation
// of gotest.
func RunBenchmarks(matchString func(pat, str string) (bool, os.Error), benchmarks []InternalBenchmark) {
// If no flag was specified, don't run benchmarks.
if len(*matchBenchmarks) == 0 {
return
}
for _, Benchmark := range benchmarks {
matched, err := matchString(*matchBenchmarks, Benchmark.Name)
if err != nil {
println("invalid regexp for -test.bench:", err.String())
os.Exit(1)
}
if !matched {
continue
}
b := &B{benchmark: Benchmark}
r := b.run()
fmt.Printf("%s\t%v\n", Benchmark.Name, r)
}
}
// Benchmark benchmarks a single function. Useful for creating
// custom benchmarks that do not use gotest.
func Benchmark(f func(b *B)) BenchmarkResult {
b := &B{benchmark: InternalBenchmark{"", f}}
return b.run()
}
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