ceremonyclient/pebble/internal/randvar/zipf_test.go
Cassandra Heart 2e2a1e4789
v1.2.0 (#31)
2024-01-03 01:31:42 -06:00

130 lines
3.2 KiB
Go

// Copyright 2017 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License. See the AUTHORS file
// for names of contributors.
package randvar
import (
"math"
"testing"
"github.com/stretchr/testify/require"
)
func TestZeta(t *testing.T) {
var zetaTests = []struct {
n uint64
theta float64
expected float64
}{
{20, 0.99, 3.64309060779367},
{200, 0.99, 6.02031118558},
{1000, 0.99, 7.72895321728},
{2000, 0.99, 8.47398788329},
{10000, 0.99, 10.2243614596},
{100000, 0.99, 12.7783380626},
{1000000, 0.99, 15.391849746},
{10000000, 0.99, 18.066242575},
// TODO(peter): The last test case takes an excessively long time to run (7s).
// {100000000, 0.99, 20.80293049},
}
t.Run("FromScratch", func(t *testing.T) {
for _, test := range zetaTests {
computedZeta := computeZetaFromScratch(test.n, test.theta)
if math.Abs(computedZeta-test.expected) > 0.000000001 {
t.Fatalf("expected %6.4f, got %6.4f", test.expected, computedZeta)
}
}
})
t.Run("Incrementally", func(t *testing.T) {
// Theta cannot be 1 by definition, so this is a safe initial value.
oldTheta := 1.0
var oldZetaN float64
var oldN uint64
for _, test := range zetaTests {
// If theta has changed, recompute from scratch
if test.theta != oldTheta {
oldZetaN = computeZetaFromScratch(test.n, test.theta)
oldN = test.n
continue
}
computedZeta := computeZetaIncrementally(oldN, test.n, test.theta, oldZetaN)
if math.Abs(computedZeta-test.expected) > 0.000000001 {
t.Fatalf("expected %6.4f, got %6.4f", test.expected, computedZeta)
}
oldZetaN = computedZeta
oldN = test.n
}
})
}
func TestZetaIncMax(t *testing.T) {
// Construct a zipf generator covering the range [0,10] incrementally.
z0, err := NewZipf(0, 0, 0.99)
require.NoError(t, err)
for i := 0; i < 10; i++ {
z0.IncMax(1)
}
// Construct a zipf generator covering the range [0,10] via the constructor.
z10, err := NewZipf(0, 10, 0.99)
require.NoError(t, err)
z0.mu.Lock()
defer z0.mu.Unlock()
z10.mu.Lock()
defer z10.mu.Unlock()
if z0.mu.zetaN != z10.mu.zetaN {
t.Fatalf("expected zetaN %v, but found %v", z10.mu.zetaN, z0.mu.zetaN)
}
if z0.mu.eta != z10.mu.eta {
t.Fatalf("expected eta %v, but found %v", z10.mu.eta, z0.mu.eta)
}
}
func TestNewZipf(t *testing.T) {
var gens = []struct {
min, max uint64
theta float64
}{
{0, 100, 0.99},
{0, 100, 1.01},
}
for _, gen := range gens {
_, err := NewZipf(gen.min, gen.max, gen.theta)
require.NoError(t, err)
}
}
func TestZipf(t *testing.T) {
rng := NewRand()
z, err := NewZipf(0, 99, 0.99)
require.NoError(t, err)
x := make([]int, 10000)
for i := range x {
x[i] = int(z.Uint64(rng))
}
if testing.Verbose() {
dumpSamples(x)
}
}