1 files changed, 236 insertions, 0 deletions
diff --git a/src/pkg/testing/benchmark.go b/src/pkg/testing/benchmark.go
new file mode 100644
index 000000000..fd0bd8665
--- /dev/null
+++ b/src/pkg/testing/benchmark.go
@@ -0,0 +1,236 @@
+// 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 {
+	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() {
+	if b.start == 0 {
+		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 sets the elapsed benchmark time to zero.
+// It does not affect whether the timer is running.
+func (b *B) ResetTimer() {
+	if b.start > 0 {
+		b.start = time.Nanoseconds()
+	}
+	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 the specified amount of time.
+	time := int64(*benchTime * 1e9)
+	for b.ns < time && n < 1e9 {
+		last := n
+		// Predict iterations/sec.
+		if b.nsPerOp() == 0 {
+			n = 1e9
+		} else {
+			n = int(time / 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 // Bytes processed in one iteration.
+}
+
+func (r BenchmarkResult) NsPerOp() int64 {
+	if r.N <= 0 {
+		return 0
+	}
+	return r.Ns / int64(r.N)
+}
+
+func (r BenchmarkResult) mbPerSec() float64 {
+	if r.Bytes <= 0 || r.Ns <= 0 || r.N <= 0 {
+		return 0
+	}
+	return float64(r.Bytes) * float64(r.N) / float64(r.Ns) * 1e3
+}
+
+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.Ns)/float64(r.N))
+		} else {
+			ns = fmt.Sprintf("%12.1f ns/op", float64(r.Ns)/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, 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
+		}
+		for _, procs := range cpuList {
+			runtime.GOMAXPROCS(procs)
+			b := &B{benchmark: Benchmark}
+			benchName := Benchmark.Name
+			if procs != 1 {
+				benchName = fmt.Sprintf("%s-%d", Benchmark.Name, procs)
+			}
+			print(fmt.Sprintf("%s\t", benchName))
+			r := b.run()
+			print(fmt.Sprintf("%v\n", r))
+			if p := runtime.GOMAXPROCS(-1); p != procs {
+				print(fmt.Sprintf("%s left GOMAXPROCS set to %d\n", benchName, p))
+			}
+		}
+	}
+}
+
+// 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()
+}