Subversion Repositories openrisc

// 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")
var benchTime = flag.Float64("test.benchtime", 1, "approximate run time for each benchmark, in seconds")

// 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 {
        common
        N         int
        benchmark InternalBenchmark
        bytes     int64
        timerOn   bool
        result    BenchmarkResult
}

// 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() {
        if !b.timerOn {
                b.start = time.Now()
                b.timerOn = true
        }
}

// 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.timerOn {
                b.duration += time.Now().Sub(b.start)
                b.timerOn = false
        }
}

// ResetTimer sets the elapsed benchmark time to zero.
// It does not affect whether the timer is running.
func (b *B) ResetTimer() {
        if b.timerOn {
                b.start = time.Now()
        }
        b.duration = 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.duration.Nanoseconds() / 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 in a separate goroutine.
func (b *B) run() BenchmarkResult {
        go b.launch()
        <-b.signal
        return b.result
}

// launch launches 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
// launch is run by the fun function as a separate goroutine.
func (b *B) launch() {
        // Run the benchmark for a single iteration in case it's expensive.
        n := 1

        // Signal that we're done whether we return normally
        // or by FailNow's runtime.Goexit.
        defer func() {
                b.signal <- b
        }()

        b.runN(n)
        // Run the benchmark for at least the specified amount of time.
        d := time.Duration(*benchTime * float64(time.Second))
        for !b.failed && b.duration < d && n < 1e9 {
                last := n
                // Predict iterations/sec.
                if b.nsPerOp() == 0 {
                        n = 1e9
                } else {
                        n = int(d.Nanoseconds() / 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)
        }
        b.result = BenchmarkResult{b.N, b.duration, b.bytes}
}

// The results of a benchmark run.
type BenchmarkResult struct {
        N     int           // The number of iterations.
        T     time.Duration // The total time taken.
        Bytes int64         // Bytes processed in one iteration.
}

func (r BenchmarkResult) NsPerOp() int64 {
        if r.N <= 0 {
                return 0
        }
        return r.T.Nanoseconds() / int64(r.N)
}

func (r BenchmarkResult) mbPerSec() float64 {
        if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 {
                return 0
        }
        return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds()
}

func (r BenchmarkResult) String() string {
        mbs := r.mbPerSec()
        mb := ""
        if mbs != 0 {
                mb = fmt.Sprintf("\t%7.2f MB/s", mbs)
        }
        nsop := r.NsPerOp()
        ns := fmt.Sprintf("%10d ns/op", nsop)
        if r.N > 0 && nsop < 100 {
                // The format specifiers here make sure that
                // the ones digits line up for all three possible formats.
                if nsop < 10 {
                        ns = fmt.Sprintf("%13.2f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
                } else {
                        ns = fmt.Sprintf("%12.1f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
                }
        }
        return fmt.Sprintf("%8d\t%s%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, 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 {
                        fmt.Fprintf(os.Stderr, "testing: invalid regexp for -test.bench: %s\n", err)
                        os.Exit(1)
                }
                if !matched {
                        continue
                }
                for _, procs := range cpuList {
                        runtime.GOMAXPROCS(procs)
                        b := &B{
                                common: common{
                                        signal: make(chan interface{}),
                                },
                                benchmark: Benchmark,
                        }
                        benchName := Benchmark.Name
                        if procs != 1 {
                                benchName = fmt.Sprintf("%s-%d", Benchmark.Name, procs)
                        }
                        fmt.Printf("%s\t", benchName)
                        r := b.run()
                        if b.failed {
                                // The output could be very long here, but probably isn't.
                                // We print it all, regardless, because we don't want to trim the reason
                                // the benchmark failed.
                                fmt.Printf("--- FAIL: %s\n%s", benchName, b.output)
                                continue
                        }
                        fmt.Printf("%v\n", r)
                        // Unlike with tests, we ignore the -chatty flag and always print output for
                        // benchmarks since the output generation time will skew the results.
                        if len(b.output) > 0 {
                                b.trimOutput()
                                fmt.Printf("--- BENCH: %s\n%s", benchName, b.output)
                        }
                        if p := runtime.GOMAXPROCS(-1); p != procs {
                                fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p)
                        }
                }
        }
}

// trimOutput shortens the output from a benchmark, which can be very long.
func (b *B) trimOutput() {
        // The output is likely to appear multiple times because the benchmark
        // is run multiple times, but at least it will be seen. This is not a big deal
        // because benchmarks rarely print, but just in case, we trim it if it's too long.
        const maxNewlines = 10
        for nlCount, j := 0, 0; j < len(b.output); j++ {
                if b.output[j] == '\n' {
                        nlCount++
                        if nlCount >= maxNewlines {
                                b.output = append(b.output[:j], "\n\t... [output truncated]\n"...)
                                break
                        }
                }
        }
}

// Benchmark benchmarks a single function. Useful for creating
// custom benchmarks that do not use gotest.
func Benchmark(f func(b *B)) BenchmarkResult {
        b := &B{
                common: common{
                        signal: make(chan interface{}),
                },
                benchmark: InternalBenchmark{"", f},
        }
        return b.run()
}