compress/flate: add Encoder/Decoder benchmarks

In CL 6127051, nigeltao suggested that further gains
were possible by improving the performance of flate.
This CL adds a set of benchmarks (based on compress/lzw)
that can be used to judge any future improvements.

R=nigeltao
CC=golang-dev
https://golang.org/cl/6128049

src/pkg/compress/flate/reader_test.go

+// Copyright 2012 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 flate
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"runtime"
+	"testing"
+)
+
+func benchmarkDecoder(b *testing.B, level, n int) {
+	b.StopTimer()
+	b.SetBytes(int64(n))
+	buf0, err := ioutil.ReadFile("../testdata/e.txt")
+	if err != nil {
+		b.Fatal(err)
+	}
+	buf0 = buf0[:10000]
+	compressed := new(bytes.Buffer)
+	w, err := NewWriter(compressed, level)
+	if err != nil {
+		b.Fatal(err)
+	}
+	for i := 0; i < n; i += len(buf0) {
+		io.Copy(w, bytes.NewBuffer(buf0))
+	}
+	w.Close()
+	buf1 := compressed.Bytes()
+	buf0, compressed, w = nil, nil, nil
+	runtime.GC()
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		io.Copy(ioutil.Discard, NewReader(bytes.NewBuffer(buf1)))
+	}
+}
+
+func BenchmarkDecoderBestSpeed1K(b *testing.B) {
+	benchmarkDecoder(b, BestSpeed, 1e4)
+}
+
+func BenchmarkDecoderBestSpeed10K(b *testing.B) {
+	benchmarkDecoder(b, BestSpeed, 1e5)
+}
+
+func BenchmarkDecoderBestSpeed100K(b *testing.B) {
+	benchmarkDecoder(b, BestSpeed, 1e6)
+}
+
+func BenchmarkDecoderDefaultCompression1K(b *testing.B) {
+	benchmarkDecoder(b, DefaultCompression, 1e4)
+}
+
+func BenchmarkDecoderDefaultCompression10K(b *testing.B) {
+	benchmarkDecoder(b, DefaultCompression, 1e5)
+}
+
+func BenchmarkDecoderDefaultCompression100K(b *testing.B) {
+	benchmarkDecoder(b, DefaultCompression, 1e6)
+}
+
+func BenchmarkDecoderBestCompression1K(b *testing.B) {
+	benchmarkDecoder(b, BestCompression, 1e4)
+}
+
+func BenchmarkDecoderBestCompression10K(b *testing.B) {
+	benchmarkDecoder(b, BestCompression, 1e5)
+}
+
+func BenchmarkDecoderBestCompression100K(b *testing.B) {
+	benchmarkDecoder(b, BestCompression, 1e6)
+}

src/pkg/compress/flate/writer_test.go

+// Copyright 2012 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 flate
+
+import (
+	"io/ioutil"
+	"runtime"
+	"testing"
+)
+
+func benchmarkEncoder(b *testing.B, level, n int) {
+	b.StopTimer()
+	b.SetBytes(int64(n))
+	buf0, err := ioutil.ReadFile("../testdata/e.txt")
+	if err != nil {
+		b.Fatal(err)
+	}
+	buf0 = buf0[:10000]
+	buf1 := make([]byte, n)
+	for i := 0; i < n; i += len(buf0) {
+		copy(buf1[i:], buf0)
+	}
+	buf0 = nil
+	runtime.GC()
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		w, err := NewWriter(ioutil.Discard, level)
+		if err != nil {
+			b.Fatal(err)
+		}
+		w.Write(buf1)
+		w.Close()
+	}
+}
+
+func BenchmarkEncoderBestSpeed1K(b *testing.B) {
+	benchmarkEncoder(b, BestSpeed, 1e4)
+}
+
+func BenchmarkEncoderBestSpeed10K(b *testing.B) {
+	benchmarkEncoder(b, BestSpeed, 1e5)
+}
+
+func BenchmarkEncoderBestSpeed100K(b *testing.B) {
+	benchmarkEncoder(b, BestSpeed, 1e6)
+}
+
+func BenchmarkEncoderDefaultCompression1K(b *testing.B) {
+	benchmarkEncoder(b, DefaultCompression, 1e4)
+}
+
+func BenchmarkEncoderDefaultCompression10K(b *testing.B) {
+	benchmarkEncoder(b, DefaultCompression, 1e5)
+}
+
+func BenchmarkEncoderDefaultCompression100K(b *testing.B) {
+	benchmarkEncoder(b, DefaultCompression, 1e6)
+}
+
+func BenchmarkEncoderBestCompression1K(b *testing.B) {
+	benchmarkEncoder(b, BestCompression, 1e4)
+}
+
+func BenchmarkEncoderBestCompression10K(b *testing.B) {
+	benchmarkEncoder(b, BestCompression, 1e5)
+}
+
+func BenchmarkEncoderBestCompression100K(b *testing.B) {
+	benchmarkEncoder(b, BestCompression, 1e6)
+}