Add sumOfSquares to histogram

benchmark/stats/histogram.go

@@ -15,6 +15,8 @@ type HistogramValue struct {
 	Count int64
 	// Sum is the sum of all the values added to the histogram.
 	Sum int64
+	// SumOfSquares is the sum of squares of all values.
+	SumOfSquares int64
 	// Min is the minimum of all the values added to the histogram.
 	Min int64
 	// Max is the maximum of all the values added to the histogram.
@@ -82,6 +84,7 @@ type Histogram struct {
 	buckets      []bucketInternal
 	count        *Counter
 	sum          *Counter
+	sumOfSquares *Counter
 	tracker      *Tracker
 }
 
@@ -120,6 +123,7 @@ func NewHistogram(opts HistogramOptions) *Histogram {
 		buckets:      make([]bucketInternal, opts.NumBuckets),
 		count:        newCounter(),
 		sum:          newCounter(),
+		sumOfSquares: newCounter(),
 		tracker:      newTracker(),
 	}
 	low := opts.MinValue
@@ -147,6 +151,7 @@ func (h *Histogram) Add(value int64) error {
 	h.buckets[bucket].count.Incr(1)
 	h.count.Incr(1)
 	h.sum.Incr(value)
+	h.sumOfSquares.Incr(value * value)
 	h.tracker.Push(value)
 	return nil
 }
@@ -169,6 +174,7 @@ func (h *Histogram) Value() HistogramValue {
 	v := HistogramValue{
 		Count:        h.count.Value(),
 		Sum:          h.sum.Value(),
+		SumOfSquares: h.sumOfSquares.Value(),
 		Min:          h.tracker.Min(),
 		Max:          h.tracker.Max(),
 		Buckets:      b,
@@ -189,6 +195,7 @@ func (h *Histogram) Delta1h() HistogramValue {
 	v := HistogramValue{
 		Count:        h.count.Delta1h(),
 		Sum:          h.sum.Delta1h(),
+		SumOfSquares: h.sumOfSquares.Delta1h(),
 		Min:          h.tracker.Min1h(),
 		Max:          h.tracker.Max1h(),
 		Buckets:      b,
@@ -209,6 +216,7 @@ func (h *Histogram) Delta10m() HistogramValue {
 	v := HistogramValue{
 		Count:        h.count.Delta10m(),
 		Sum:          h.sum.Delta10m(),
+		SumOfSquares: h.sumOfSquares.Delta10m(),
 		Min:          h.tracker.Min10m(),
 		Max:          h.tracker.Max10m(),
 		Buckets:      b,
@@ -229,6 +237,7 @@ func (h *Histogram) Delta1m() HistogramValue {
 	v := HistogramValue{
 		Count:        h.count.Delta1m(),
 		Sum:          h.sum.Delta1m(),
+		SumOfSquares: h.sumOfSquares.Delta1m(),
 		Min:          h.tracker.Min1m(),
 		Max:          h.tracker.Max1m(),
 		Buckets:      b,