shrink the samples buffer and add a script to generate blog post table

quantile/stream.go

@@ -130,7 +130,7 @@ type Stream struct {
 
 func newStream(ƒ invariant) *Stream {
 	x := &stream{ƒ: ƒ}
-	return &Stream{x, make(Samples, 0, 500), true}
+	return &Stream{x, make(Samples, 0, 10), true}
 }
 
 // Insert inserts v into the stream.

test.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"fmt"
+	"github.com/beorn7/perks/quantile"
+)
+
+func main() {
+	t := quantile.NewTargeted(map[float64]float64{
+		0.5: 0.05, 0.9: 0.01, 0.99: 0.001,
+	})
+	input := []float64{16, 3, 5, 18, 4, 14, 11, 15, 17, 12, 6, 8, 10, 13, 2, 24, 25, 26, 23, 27, 28, 20, 19, 7, 22, 21, 29, 1, 30, 9}
+	fmt.Printf("Data stream: %v\n", input)
+	inflex := 10
+	for i := 0; i < inflex; i ++ {
+		t.Insert(input[i])
+	}
+	fmt.Printf("Action    |                         Samples                         | 0.5 | 0.9 | 0.99 | Removed | Added\n")
+	fmt.Printf("----------+---------------------------------------------------------+-----+-----+------+---------+------\n")
+	fmt.Printf("First 10  | %-55v | %3.0f | %3.0f | %4.0f |       0 |    0 \n",
+		prints(t.Samples()), t.Query(0.5), t.Query(0.9), t.Query(0.99))
+	var newSamples, oldSamples = quantile.Samples{}, quantile.Samples{}
+	for i := inflex; i < len(input); i ++ {
+		t.Insert(input[i])
+		newSamples = clone(t.Samples())
+		removed, added := diff(oldSamples, newSamples)
+		fmt.Printf("Insert %2.0f | %-55v | %3.0f | %3.0f | %4.0f | %7.0f | %4.0f\n",
+			input[i], prints(newSamples), t.Query(0.5), t.Query(0.9), t.Query(0.99), removed, added)
+		oldSamples = clone(newSamples)
+	}
+}
+
+func prints(samples quantile.Samples) string {
+	out := make([]float64, len(samples))
+	for i, s := range samples {
+		out[i] = s.Value
+	}
+	return fmt.Sprintf("%v", out)
+}
+
+func clone(samples quantile.Samples) quantile.Samples {
+	c := make(quantile.Samples, len(samples), len(samples))
+	copy(c, samples)
+	return c
+}
+
+func diff(old, new quantile.Samples) (removed, added float64) {
+	oldIndex := make(map[float64]struct{}, len(old))
+	for _, s := range old {
+		oldIndex[s.Value] = struct{}{}
+	}
+	newIndex := make(map[float64]struct{}, len(new))
+	for _, s := range new {
+		newIndex[s.Value] = struct{}{}
+	}
+	for _, s := range old {
+		if _, ok := newIndex[s.Value]; !ok {
+			removed = s.Value
+			break
+		}
+	}
+	for _, s := range new {
+		if _, ok := oldIndex[s.Value]; !ok {
+			added = s.Value
+			break
+		}
+	}
+	return removed, added
+}
+