avoid using pointers for SumEntry

stream.go

@@ -73,7 +73,7 @@ func (stream *Stream) pushBuffer(buf *buffer) error {
 }
 
 // PushSummary pushes full summary while maintaining approximation error invariants.
-func (stream *Stream) PushSummary(summary []*SumEntry) error {
+func (stream *Stream) PushSummary(summary []SumEntry) error {
 	// Validate state.
 	if stream.finalized {
 		return fmt.Errorf("Finalize() already called")

stream_test.go

@@ -217,7 +217,7 @@ func testDistributedStreams(t *testing.T, numWorkers int32, eps float64, maxElem
 
 	// Simulate streams on each worker running independently
 	totalWeight := 0.0
-	workerSummaries := [][]*SumEntry{}
+	workerSummaries := [][]SumEntry{}
 	for i := int32(0); i < numWorkers; i++ {
 		stream, err := New(eps/2, maxElements)
 		if err != nil {

summary.go

@@ -18,24 +18,34 @@ func (se SumEntry) nextMinRank() float64 {
 
 // Summary ...
 type Summary struct {
-	entries []*SumEntry
+	entries []SumEntry
 }
 
 // newSummary ...
 func newSummary() *Summary {
 	return &Summary{
-		entries: make([]*SumEntry, 0),
+		entries: make([]SumEntry, 0),
 	}
 }
 
+func (sum *Summary) clone() *Summary {
+	newSum := &Summary{
+		entries: make([]SumEntry, len(sum.entries)),
+	}
+	for i, entry := range sum.entries {
+		newSum.entries[i] = entry
+	}
+	return newSum
+}
+
 // buildFromBufferEntries ...
 func (sum *Summary) buildFromBufferEntries(bes []bufEntry) {
-	sum.entries = []*SumEntry{}
+	sum.entries = []SumEntry{}
 	// TODO: entries_.reserve(buffer_entries.size());
 	cumWeight := 0.0
 	for _, entry := range bes {
 		curWeight := entry.weight
-		se := &SumEntry{
+		se := SumEntry{
 			Value:   entry.value,
 			Weight:  entry.weight,
 			MinRank: cumWeight,
@@ -47,8 +57,8 @@ func (sum *Summary) buildFromBufferEntries(bes []bufEntry) {
 }
 
 // BuildFromSummaryEntries ...
-func (sum *Summary) BuildFromSummaryEntries(ses []*SumEntry) {
-	sum.entries = make([]*SumEntry, len(ses))
+func (sum *Summary) BuildFromSummaryEntries(ses []SumEntry) {
+	sum.entries = make([]SumEntry, len(ses))
 	for i, entry := range ses {
 		sum.entries[i] = entry
 	}
@@ -65,11 +75,11 @@ func (sum *Summary) Merge(other *Summary) {
 		return
 	}
 
-	baseEntries := make([]*SumEntry, len(sum.entries))
+	baseEntries := make([]SumEntry, len(sum.entries))
 	for i, e := range sum.entries {
 		baseEntries[i] = e
 	}
-	sum.entries = []*SumEntry{}
+	sum.entries = []SumEntry{}
 
 	// Merge entries maintaining ranks. The idea is to stack values
 	// in order which we can do in linear time as the two summaries are
@@ -89,23 +99,23 @@ func (sum *Summary) Merge(other *Summary) {
 		it1 := baseEntries[i]
 		it2 := otherEntries[j]
 		if it1.Value < it2.Value {
-			sum.entries = append(sum.entries, &SumEntry{
+			sum.entries = append(sum.entries, SumEntry{
 				Value: it1.Value, Weight: it1.Weight,
 				MinRank: it1.MinRank + nextMinRank2,
 				MaxRank: it1.MaxRank + it2.prevMaxRank(),
 			})
 			nextMinRank1 = it1.nextMinRank()
 			i++
 		} else if it1.Value > it2.Value {
-			sum.entries = append(sum.entries, &SumEntry{
+			sum.entries = append(sum.entries, SumEntry{
 				Value: it2.Value, Weight: it2.Weight,
 				MinRank: it2.MinRank + nextMinRank1,
 				MaxRank: it2.MaxRank + it1.prevMaxRank(),
 			})
 			nextMinRank2 = it2.nextMinRank()
 			j++
 		} else {
-			sum.entries = append(sum.entries, &SumEntry{
+			sum.entries = append(sum.entries, SumEntry{
 				Value: it1.Value, Weight: it1.Weight + it2.Weight,
 				MinRank: it1.MinRank + it2.MinRank,
 				MaxRank: it1.MaxRank + it2.MaxRank,
@@ -120,7 +130,7 @@ func (sum *Summary) Merge(other *Summary) {
 	// Fill in any residual.
 	for i != len(baseEntries) {
 		it1 := baseEntries[i]
-		sum.entries = append(sum.entries, &SumEntry{
+		sum.entries = append(sum.entries, SumEntry{
 			Value: it1.Value, Weight: it1.Weight,
 			MinRank: it1.MinRank + nextMinRank2,
 			MaxRank: it1.MaxRank + otherEntries[len(otherEntries)-1].MaxRank,
@@ -129,7 +139,7 @@ func (sum *Summary) Merge(other *Summary) {
 	}
 	for j != len(otherEntries) {
 		it2 := otherEntries[j]
-		sum.entries = append(sum.entries, &SumEntry{
+		sum.entries = append(sum.entries, SumEntry{
 			Value: it2.Value, Weight: it2.Weight,
 			MinRank: it2.MinRank + nextMinRank1,
 			MaxRank: it2.MaxRank + baseEntries[len(baseEntries)-1].MaxRank,
@@ -293,5 +303,5 @@ func (sum *Summary) Size() int64 {
 
 // Clear ...
 func (sum *Summary) Clear() {
-	sum.entries = []*SumEntry{}
+	sum.entries = []SumEntry{}
 }

summary_test.go

@@ -24,7 +24,7 @@ type SummaryDummy struct {
 
 func NewWeightedQuantilesSummaryDummy() (*SummaryDummy, error) {
 	sum := &Summary{
-		entries: make([]*SumEntry, 0),
+		entries: make([]SumEntry, 0),
 	}
 	wqsd := &SummaryDummy{
 		Summary:            sum,
@@ -108,7 +108,7 @@ func TestSummaryBuildFromBuffer(t *testing.T) {
 	exp := SumEntry{
 		Value: -13, Weight: 4, MinRank: 0, MaxRank: 4,
 	}
-	if val := entries[0]; *val != exp {
+	if val := entries[0]; val != exp {
 		t.Errorf("expected %v, got %v", exp, val)
 	}
 
@@ -122,7 +122,7 @@ func TestSummaryBuildFromBuffer(t *testing.T) {
 	exp = SumEntry{
 		Value: 21, Weight: 8, MinRank: 37, MaxRank: 45,
 	}
-	if val := entries[len(entries)-1]; *val != exp {
+	if val := entries[len(entries)-1]; val != exp {
 		t.Errorf("expected %v, got %v", exp, val)
 	}