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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package exemplar
import (
"context"
"math"
"math/rand"
"slices"
"testing"
"time"
"github.com/stretchr/testify/assert"
)
func TestNewFixedSizeReservoir(t *testing.T) {
t.Run("Int64", ReservoirTest[int64](func(n int) (Reservoir, int) {
return NewFixedSizeReservoir(n), n
}))
t.Run("Float64", ReservoirTest[float64](func(n int) (Reservoir, int) {
return NewFixedSizeReservoir(n), n
}))
}
func TestNewFixedSizeReservoirSamplingCorrectness(t *testing.T) {
intensity := 0.1
sampleSize := 1000
rng := rand.New(rand.NewSource(time.Now().UnixNano()))
data := make([]float64, sampleSize*1000)
for i := range data {
// Generate exponentially distributed data.
data[i] = (-1.0 / intensity) * math.Log(rng.Float64())
}
// Sort to test position bias.
slices.Sort(data)
r := NewFixedSizeReservoir(sampleSize)
for _, value := range data {
r.Offer(context.Background(), staticTime, NewValue(value), nil)
}
var sum float64
for _, m := range r.store {
sum += m.Value.Float64()
}
mean := sum / float64(sampleSize)
// Check the intensity/rate of the sampled distribution is preserved
// ensuring no bias in our random sampling algorithm.
assert.InDelta(t, 1/mean, intensity, 0.02) // Within 5σ.
}
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