Optimize FirstUniqueStrings and FirstUniquePaths (27027c76) · Commits · e / os / android_build_soong

android/paths.go

+22 −0

Original line number	Diff line number	Diff line
		@@ -470,6 +470,14 @@ func (p Paths) Strings() []string {
		// FirstUniquePaths returns all unique elements of a Paths, keeping the first copy of each. It
		// modifies the Paths slice contents in place, and returns a subslice of the original slice.
		func FirstUniquePaths(list Paths) Paths {
		// 128 was chosen based on BenchmarkFirstUniquePaths results.
		if len(list) > 128 {
		return firstUniquePathsMap(list)
		}
		return firstUniquePathsList(list)
		}

		func firstUniquePathsList(list Paths) Paths {
		k := 0
		outer:
		for i := 0; i < len(list); i++ {
		@@ -484,6 +492,20 @@ outer:
		return list[:k]
		}

		func firstUniquePathsMap(list Paths) Paths {
		k := 0
		seen := make(map[Path]bool, len(list))
		for i := 0; i < len(list); i++ {
		if seen[list[i]] {
		continue
		}
		seen[list[i]] = true
		list[k] = list[i]
		k++
		}
		return list[:k]
		}

		// LastUniquePaths returns all unique elements of a Paths, keeping the last copy of each. It
		// modifies the Paths slice contents in place, and returns a subslice of the original slice.
		func LastUniquePaths(list Paths) Paths {

android/paths_test.go

+49 −0

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@ import (
		"errors"
		"fmt"
		"reflect"
		"strconv"
		"strings"
		"testing"

		@@ -1255,3 +1256,51 @@ func ExampleOutputPath_FileInSameDir() {
		// out/system/framework/boot.art out/system/framework/oat/arm/boot.vdex
		// boot.art oat/arm/boot.vdex
		}

		func BenchmarkFirstUniquePaths(b *testing.B) {
		implementations := []struct {
		name string
		f func(Paths) Paths
		}{
		{
		name: "list",
		f: firstUniquePathsList,
		},
		{
		name: "map",
		f: firstUniquePathsMap,
		},
		}
		const maxSize = 1024
		uniquePaths := make(Paths, maxSize)
		for i := range uniquePaths {
		uniquePaths[i] = PathForTesting(strconv.Itoa(i))
		}
		samePath := make(Paths, maxSize)
		for i := range samePath {
		samePath[i] = uniquePaths[0]
		}

		f := func(b *testing.B, imp func(Paths) Paths, paths Paths) {
		for i := 0; i < b.N; i++ {
		b.ReportAllocs()
		paths = append(Paths(nil), paths...)
		imp(paths)
		}
		}

		for n := 1; n <= maxSize; n <<= 1 {
		b.Run(strconv.Itoa(n), func(b *testing.B) {
		for _, implementation := range implementations {
		b.Run(implementation.name, func(b *testing.B) {
		b.Run("same", func(b *testing.B) {
		f(b, implementation.f, samePath[:n])
		})
		b.Run("unique", func(b *testing.B) {
		f(b, implementation.f, uniquePaths[:n])
		})
		})
		}
		})
		}
		}

android/util.go

+22 −0

Original line number	Diff line number	Diff line
		@@ -193,6 +193,14 @@ func RemoveFromList(s string, list []string) (bool, []string) {
		// FirstUniqueStrings returns all unique elements of a slice of strings, keeping the first copy of
		// each. It modifies the slice contents in place, and returns a subslice of the original slice.
		func FirstUniqueStrings(list []string) []string {
		// 128 was chosen based on BenchmarkFirstUniqueStrings results.
		if len(list) > 128 {
		return firstUniqueStringsMap(list)
		}
		return firstUniqueStringsList(list)
		}

		func firstUniqueStringsList(list []string) []string {
		k := 0
		outer:
		for i := 0; i < len(list); i++ {
		@@ -207,6 +215,20 @@ outer:
		return list[:k]
		}

		func firstUniqueStringsMap(list []string) []string {
		k := 0
		seen := make(map[string]bool, len(list))
		for i := 0; i < len(list); i++ {
		if seen[list[i]] {
		continue
		}
		seen[list[i]] = true
		list[k] = list[i]
		k++
		}
		return list[:k]
		}

		// LastUniqueStrings returns all unique elements of a slice of strings, keeping the last copy of
		// each. It modifies the slice contents in place, and returns a subslice of the original slice.
		func LastUniqueStrings(list []string) []string {

android/util_test.go

+64 −5

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@ package android
		import (
		"fmt"
		"reflect"
		"strconv"
		"testing"
		)

		@@ -59,15 +60,25 @@ var firstUniqueStringsTestCases = []struct {
		}

		func TestFirstUniqueStrings(t *testing.T) {
		for _, testCase := range firstUniqueStringsTestCases {
		out := FirstUniqueStrings(testCase.in)
		if !reflect.DeepEqual(out, testCase.out) {
		f := func(t *testing.T, imp func([]string) []string, in, want []string) {
		t.Helper()
		out := imp(in)
		if !reflect.DeepEqual(out, want) {
		t.Errorf("incorrect output:")
		t.Errorf(" input: %#v", testCase.in)
		t.Errorf(" expected: %#v", testCase.out)
		t.Errorf(" input: %#v", in)
		t.Errorf(" expected: %#v", want)
		t.Errorf(" got: %#v", out)
		}
		}

		for _, testCase := range firstUniqueStringsTestCases {
		t.Run("list", func(t *testing.T) {
		f(t, firstUniqueStringsList, testCase.in, testCase.out)
		})
		t.Run("map", func(t *testing.T) {
		f(t, firstUniqueStringsMap, testCase.in, testCase.out)
		})
		}
		}

		var lastUniqueStringsTestCases = []struct {
		@@ -568,3 +579,51 @@ func Test_Shard(t *testing.T) {
		})
		}
		}

		func BenchmarkFirstUniqueStrings(b *testing.B) {
		implementations := []struct {
		name string
		f func([]string) []string
		}{
		{
		name: "list",
		f: firstUniqueStringsList,
		},
		{
		name: "map",
		f: firstUniqueStringsMap,
		},
		}
		const maxSize = 1024
		uniqueStrings := make([]string, maxSize)
		for i := range uniqueStrings {
		uniqueStrings[i] = strconv.Itoa(i)
		}
		sameString := make([]string, maxSize)
		for i := range sameString {
		sameString[i] = uniqueStrings[0]
		}

		f := func(b *testing.B, imp func([]string) []string, s []string) {
		for i := 0; i < b.N; i++ {
		b.ReportAllocs()
		s = append([]string(nil), s...)
		imp(s)
		}
		}

		for n := 1; n <= maxSize; n <<= 1 {
		b.Run(strconv.Itoa(n), func(b *testing.B) {
		for _, implementation := range implementations {
		b.Run(implementation.name, func(b *testing.B) {
		b.Run("same", func(b *testing.B) {
		f(b, implementation.f, sameString[:n])
		})
		b.Run("unique", func(b *testing.B) {
		f(b, implementation.f, uniqueStrings[:n])
		})
		})
		}
		})
		}
		}