add benchmark for Settings.toInternal + optimizations (#1)

Author: achille-roussel

go.mod

@@ -0,0 +1,10 @@
+module github.com/segmentio/go-hll
+
+go 1.12
+
+require (
+	github.com/davecgh/go-spew v1.1.0
+	github.com/pkg/errors v0.8.0
+	github.com/pmezard/go-difflib v1.0.0
+	github.com/stretchr/testify v1.2.2
+)

go.sum

@@ -0,0 +1,8 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
+github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=

settings.go

@@ -130,23 +130,21 @@ type settings struct {
 // This function will also compute and populate auto-generated thresholds and
 // constant values used by the Hll calculations and cache the result.
 func (s Settings) toInternal() (*settings, error) {
-
 	if err := s.validate(); err != nil {
 		return nil, err
 	}
 
-	log2m := s.Log2m
-	regwidth := s.Regwidth
+	settingsCacheLock.RLock()
+	cachedSettings := settingsCache[s]
+	settingsCacheLock.RUnlock()
 
-	// try to get the settings
-	if settings := func() *settings {
-		settingsCacheLock.RLock()
-		defer settingsCacheLock.RUnlock()
-		return settingsCache[s]
-	}(); settings != nil {
-		return settings, nil
+	if cachedSettings != nil {
+		return cachedSettings, nil
 	}
 
+	log2m := s.Log2m
+	regwidth := s.Regwidth
+
 	var explicitThreshold int
 	explicitAuto := s.ExplicitThreshold == AutoExplicitThreshold
 	if explicitAuto {

settings_test.go

@@ -136,3 +136,14 @@ func resetDefaults() {
 	defaultSettings = nil
 	defaultSettingsLock.Unlock()
 }
+
+func BenchmarkSettingsToInternal(b *testing.B) {
+	s := Settings{
+		Log2m:    11,
+		Regwidth: 5,
+	}
+
+	for i := 0; i < b.N; i++ {
+		s.toInternal()
+	}
+}