From ec02e9ba191217fc31c6a27ef131ca9c51ae1425 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Wed, 7 Feb 2024 21:43:24 +0200
Subject: [PATCH] lib/protoparser/datadogsketches: use math.RoundToEven() for
calculating the rank
The original code uses this function - see https://github.com/DataDog/opentelemetry-mapping-go/blob/48d52eeea60d28da2e14c154a24557c4d290c6e2/pkg/quantile/sparse.go#L138
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5775
---
lib/protoparser/datadogsketches/parser.go | 2 +-
lib/protoparser/datadogsketches/parser_test.go | 18 ++++++++++--------
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/lib/protoparser/datadogsketches/parser.go b/lib/protoparser/datadogsketches/parser.go
index ec2b212686..9957f9d63e 100644
--- a/lib/protoparser/datadogsketches/parser.go
+++ b/lib/protoparser/datadogsketches/parser.go
@@ -303,7 +303,7 @@ func (d *Dogsketch) quantile(q float64) float64 {
return 0
}
- rank := q * float64(d.Cnt-1)
+ rank := math.RoundToEven(q * float64(d.Cnt-1))
cnt := float64(0)
for i, n := range ns {
cnt += float64(n)
diff --git a/lib/protoparser/datadogsketches/parser_test.go b/lib/protoparser/datadogsketches/parser_test.go
index 161f073ef5..c9ea5eac35 100644
--- a/lib/protoparser/datadogsketches/parser_test.go
+++ b/lib/protoparser/datadogsketches/parser_test.go
@@ -9,21 +9,23 @@ func TestDogsketchQuantile(t *testing.T) {
f := func(d *Dogsketch, q float64, vExpected float64) {
t.Helper()
v := d.quantile(q)
- if math.Abs(v-vExpected) > 0.4 {
+ if math.Abs(v-vExpected) > 0.01 {
t.Fatalf("unexpected value; got %v; want %v", v, vExpected)
}
}
sketches := &Dogsketch{
Min: 8.0,
- Max: 20.0,
+ Max: 21.0,
Cnt: 17,
N: []uint32{0x0, 0x0, 0x1, 0x0, 0x1, 0x4, 0x6, 0x1, 0x2, 0x0, 0x1, 0x0, 0x1},
K: []int32{0, 1472, 1473, 1479, 1480, 1503, 1504, 1512, 1513, 1514, 1515, 1531, 1532},
}
- f(sketches, 0.1, 8.96)
- f(sketches, 0.5, 13.01)
- f(sketches, 0.75, 14.96)
- f(sketches, 0.9, 14.96)
- f(sketches, 0.95, 15.43)
- f(sketches, 0.99, 15.43)
+ f(sketches, 0, 8)
+ f(sketches, 0.1, 12.91)
+ f(sketches, 0.5, 13.18)
+ f(sketches, 0.75, 14.84)
+ f(sketches, 0.9, 15.19)
+ f(sketches, 0.95, 15.55)
+ f(sketches, 0.99, 20.24)
+ f(sketches, 1, 21)
}