Imported Upstream version 1.4upstream/1.4

1 files changed, 446 insertions, 0 deletions

diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go
new file mode 100644
index 000000000..ffd537684
--- /dev/null
+++ b/src/testing/benchmark.go
@@ -0,0 +1,446 @@
+// 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"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
+var benchTime = flag.Duration("test.benchtime", 1*time.Second, "approximate run time for each benchmark")
+var benchmarkMemory = flag.Bool("test.benchmem", false, "print memory allocations for benchmarks")
+
+// Global lock to ensure only one benchmark runs at a time.
+var benchmarkLock sync.Mutex
+
+// Used for every benchmark for measuring memory.
+var memStats runtime.MemStats
+
+// An internal type but exported because it is cross-package; part of the implementation
+// of the "go test" command.
+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
+	previousN        int           // number of iterations in the previous run
+	previousDuration time.Duration // total duration of the previous run
+	benchmark        InternalBenchmark
+	bytes            int64
+	timerOn          bool
+	showAllocResult  bool
+	result           BenchmarkResult
+	parallelism      int // RunParallel creates parallelism*GOMAXPROCS goroutines
+	// The initial states of memStats.Mallocs and memStats.TotalAlloc.
+	startAllocs uint64
+	startBytes  uint64
+	// The net total of this test after being run.
+	netAllocs uint64
+	netBytes  uint64
+}
+
+// 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 {
+		runtime.ReadMemStats(&memStats)
+		b.startAllocs = memStats.Mallocs
+		b.startBytes = memStats.TotalAlloc
+		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)
+		runtime.ReadMemStats(&memStats)
+		b.netAllocs += memStats.Mallocs - b.startAllocs
+		b.netBytes += memStats.TotalAlloc - b.startBytes
+		b.timerOn = false
+	}
+}
+
+// ResetTimer zeros the elapsed benchmark time and memory allocation counters.
+// It does not affect whether the timer is running.
+func (b *B) ResetTimer() {
+	if b.timerOn {
+		runtime.ReadMemStats(&memStats)
+		b.startAllocs = memStats.Mallocs
+		b.startBytes = memStats.TotalAlloc
+		b.start = time.Now()
+	}
+	b.duration = 0
+	b.netAllocs = 0
+	b.netBytes = 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 }
+
+// ReportAllocs enables malloc statistics for this benchmark.
+// It is equivalent to setting -test.benchmem, but it only affects the
+// benchmark function that calls ReportAllocs.
+func (b *B) ReportAllocs() {
+	b.showAllocResult = true
+}
+
+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) {
+	benchmarkLock.Lock()
+	defer benchmarkLock.Unlock()
+	// Try to get a comparable environment for each run
+	// by clearing garbage from previous runs.
+	runtime.GC()
+	b.N = n
+	b.parallelism = 1
+	b.ResetTimer()
+	b.StartTimer()
+	b.benchmark.F(b)
+	b.StopTimer()
+	b.previousN = n
+	b.previousDuration = b.duration
+}
+
+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, 3eX, 5eX].
+func roundUp(n int) int {
+	base := roundDown10(n)
+	switch {
+	case n <= base:
+		return base
+	case n <= (2 * base):
+		return 2 * base
+	case n <= (3 * base):
+		return 3 * base
+	case n <= (5 * base):
+		return 5 * base
+	default:
+		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 the requested benchtime.
+// It prints timing information in this form
+//		testing.BenchmarkHello	100000		19 ns/op
+// launch is run by the run 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 := *benchTime
+	for !b.failed && b.duration < d && n < 1e9 {
+		last := n
+		// Predict required iterations.
+		if b.nsPerOp() == 0 {
+			n = 1e9
+		} else {
+			n = int(d.Nanoseconds() / b.nsPerOp())
+		}
+		// Run more iterations than we think we'll need (1.2x).
+		// 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/5, 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, b.netAllocs, b.netBytes}
+}
+
+// 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.
+	MemAllocs uint64        // The total number of memory allocations.
+	MemBytes  uint64        // The total number of bytes allocated.
+}
+
+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) AllocsPerOp() int64 {
+	if r.N <= 0 {
+		return 0
+	}
+	return int64(r.MemAllocs) / int64(r.N)
+}
+
+func (r BenchmarkResult) AllocedBytesPerOp() int64 {
+	if r.N <= 0 {
+		return 0
+	}
+	return int64(r.MemBytes) / int64(r.N)
+}
+
+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)
+}
+
+func (r BenchmarkResult) MemString() string {
+	return fmt.Sprintf("%8d B/op\t%8d allocs/op",
+		r.AllocedBytesPerOp(), r.AllocsPerOp())
+}
+
+// An internal function but exported because it is cross-package; part of the implementation
+// of the "go test" command.
+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
+			}
+			results := r.String()
+			if *benchmarkMemory || b.showAllocResult {
+				results += "\t" + r.MemString()
+			}
+			fmt.Println(results)
+			// 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
+			}
+		}
+	}
+}
+
+// A PB is used by RunParallel for running parallel benchmarks.
+type PB struct {
+	globalN *uint64 // shared between all worker goroutines iteration counter
+	grain   uint64  // acquire that many iterations from globalN at once
+	cache   uint64  // local cache of acquired iterations
+	bN      uint64  // total number of iterations to execute (b.N)
+}
+
+// Next reports whether there are more iterations to execute.
+func (pb *PB) Next() bool {
+	if pb.cache == 0 {
+		n := atomic.AddUint64(pb.globalN, pb.grain)
+		if n <= pb.bN {
+			pb.cache = pb.grain
+		} else if n < pb.bN+pb.grain {
+			pb.cache = pb.bN + pb.grain - n
+		} else {
+			return false
+		}
+	}
+	pb.cache--
+	return true
+}
+
+// RunParallel runs a benchmark in parallel.
+// It creates multiple goroutines and distributes b.N iterations among them.
+// The number of goroutines defaults to GOMAXPROCS. To increase parallelism for
+// non-CPU-bound benchmarks, call SetParallelism before RunParallel.
+// RunParallel is usually used with the go test -cpu flag.
+//
+// The body function will be run in each goroutine. It should set up any
+// goroutine-local state and then iterate until pb.Next returns false.
+// It should not use the StartTimer, StopTimer, or ResetTimer functions,
+// because they have global effect.
+func (b *B) RunParallel(body func(*PB)) {
+	// Calculate grain size as number of iterations that take ~100µs.
+	// 100µs is enough to amortize the overhead and provide sufficient
+	// dynamic load balancing.
+	grain := uint64(0)
+	if b.previousN > 0 && b.previousDuration > 0 {
+		grain = 1e5 * uint64(b.previousN) / uint64(b.previousDuration)
+	}
+	if grain < 1 {
+		grain = 1
+	}
+	// We expect the inner loop and function call to take at least 10ns,
+	// so do not do more than 100µs/10ns=1e4 iterations.
+	if grain > 1e4 {
+		grain = 1e4
+	}
+
+	n := uint64(0)
+	numProcs := b.parallelism * runtime.GOMAXPROCS(0)
+	var wg sync.WaitGroup
+	wg.Add(numProcs)
+	for p := 0; p < numProcs; p++ {
+		go func() {
+			defer wg.Done()
+			pb := &PB{
+				globalN: &n,
+				grain:   grain,
+				bN:      uint64(b.N),
+			}
+			body(pb)
+		}()
+	}
+	wg.Wait()
+	if n <= uint64(b.N) && !b.Failed() {
+		b.Fatal("RunParallel: body exited without pb.Next() == false")
+	}
+}
+
+// SetParallelism sets the number of goroutines used by RunParallel to p*GOMAXPROCS.
+// There is usually no need to call SetParallelism for CPU-bound benchmarks.
+// If p is less than 1, this call will have no effect.
+func (b *B) SetParallelism(p int) {
+	if p >= 1 {
+		b.parallelism = p
+	}
+}
+
+// Benchmark benchmarks a single function. Useful for creating
+// custom benchmarks that do not use the "go test" command.
+func Benchmark(f func(b *B)) BenchmarkResult {
+	b := &B{
+		common: common{
+			signal: make(chan interface{}),
+		},
+		benchmark: InternalBenchmark{"", f},
+	}
+	return b.run()
+}