compress/lzw: use Run for benchmarks

load file only once per group.

Change-Id: I965661507055e6e100506bf14d37133ecdd2cc5e
Reviewed-on: https://go-review.googlesource.com/23423Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/compress/lzw/reader_test.go

@@ -6,8 +6,10 @@ package lzw
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"io/ioutil"
+	"math"
 	"runtime"
 	"strconv"
 	"strings"
@@ -118,42 +120,37 @@ func TestReader(t *testing.T) {
 	}
 }
 
-func benchmarkDecoder(b *testing.B, n int) {
-	b.StopTimer()
-	b.SetBytes(int64(n))
-	buf0, err := ioutil.ReadFile("../testdata/e.txt")
+func BenchmarkDecoder(b *testing.B) {
+	buf, err := ioutil.ReadFile("../testdata/e.txt")
 	if err != nil {
 		b.Fatal(err)
 	}
-	if len(buf0) == 0 {
+	if len(buf) == 0 {
 		b.Fatalf("test file has no data")
 	}
-	compressed := new(bytes.Buffer)
-	w := NewWriter(compressed, LSB, 8)
-	for i := 0; i < n; i += len(buf0) {
-		if len(buf0) > n-i {
-			buf0 = buf0[:n-i]
-		}
-		w.Write(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.NewReader(buf1), LSB, 8))
-	}
-}
-
-func BenchmarkDecoder1e4(b *testing.B) {
-	benchmarkDecoder(b, 1e4)
-}
 
-func BenchmarkDecoder1e5(b *testing.B) {
-	benchmarkDecoder(b, 1e5)
-}
-
-func BenchmarkDecoder1e6(b *testing.B) {
-	benchmarkDecoder(b, 1e6)
+	for e := 4; e <= 6; e++ {
+		n := int(math.Pow10(e))
+		b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
+			b.StopTimer()
+			b.SetBytes(int64(n))
+			buf0 := buf
+			compressed := new(bytes.Buffer)
+			w := NewWriter(compressed, LSB, 8)
+			for i := 0; i < n; i += len(buf0) {
+				if len(buf0) > n-i {
+					buf0 = buf0[:n-i]
+				}
+				w.Write(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.NewReader(buf1), LSB, 8))
+			}
+		})
+	}
 }

src/compress/lzw/writer_test.go

@@ -5,9 +5,11 @@
 package lzw
 
 import (
+	"fmt"
 	"internal/testenv"
 	"io"
 	"io/ioutil"
+	"math"
 	"os"
 	"runtime"
 	"testing"
@@ -122,41 +124,34 @@ func TestSmallLitWidth(t *testing.T) {
 	}
 }
 
-func benchmarkEncoder(b *testing.B, n int) {
-	b.StopTimer()
-	b.SetBytes(int64(n))
-	buf0, err := ioutil.ReadFile("../testdata/e.txt")
+func BenchmarkEncoder(b *testing.B) {
+	buf, err := ioutil.ReadFile("../testdata/e.txt")
 	if err != nil {
 		b.Fatal(err)
 	}
-	if len(buf0) == 0 {
+	if len(buf) == 0 {
 		b.Fatalf("test file has no data")
 	}
-	buf1 := make([]byte, n)
-	for i := 0; i < n; i += len(buf0) {
-		if len(buf0) > n-i {
-			buf0 = buf0[:n-i]
+
+	for e := 4; e <= 6; e++ {
+		n := int(math.Pow10(e))
+		buf0 := buf
+		buf1 := make([]byte, n)
+		for i := 0; i < n; i += len(buf0) {
+			if len(buf0) > n-i {
+				buf0 = buf0[:n-i]
+			}
+			copy(buf1[i:], buf0)
 		}
-		copy(buf1[i:], buf0)
-	}
-	buf0 = nil
-	runtime.GC()
-	b.StartTimer()
-	for i := 0; i < b.N; i++ {
-		w := NewWriter(ioutil.Discard, LSB, 8)
-		w.Write(buf1)
-		w.Close()
+		buf0 = nil
+		runtime.GC()
+		b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
+			b.SetBytes(int64(n))
+			for i := 0; i < b.N; i++ {
+				w := NewWriter(ioutil.Discard, LSB, 8)
+				w.Write(buf1)
+				w.Close()
+			}
+		})
 	}
 }
-
-func BenchmarkEncoder1e4(b *testing.B) {
-	benchmarkEncoder(b, 1e4)
-}
-
-func BenchmarkEncoder1e5(b *testing.B) {
-	benchmarkEncoder(b, 1e5)
-}
-
-func BenchmarkEncoder1e6(b *testing.B) {
-	benchmarkEncoder(b, 1e6)
-}