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tailscale/util/rands/cheap_test.go

97 lines
1.9 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package rands
import (
"slices"
"testing"
randv2 "math/rand/v2"
)
func TestShuffleNoAllocs(t *testing.T) {
seed := randv2.Uint64()
data := make([]int, 100)
for i := range data {
data[i] = i
}
if n := testing.AllocsPerRun(1000, func() {
Shuffle(seed, data)
}); n > 0 {
t.Errorf("Rand got %v allocs per run", n)
}
}
func BenchmarkStdRandV2Shuffle(b *testing.B) {
seed := randv2.Uint64()
data := make([]int, 100)
for i := range data {
data[i] = i
}
b.ReportAllocs()
for range b.N {
// PCG is the lightest source, taking just two uint64s, the chacha8
// source has much larger state.
rng := randv2.New(randv2.NewPCG(seed, seed))
rng.Shuffle(len(data), func(i, j int) { data[i], data[j] = data[j], data[i] })
}
}
func BenchmarkLocalShuffle(b *testing.B) {
seed := randv2.Uint64()
data := make([]int, 100)
for i := range data {
data[i] = i
}
b.ReportAllocs()
for range b.N {
Shuffle(seed, data)
}
}
func TestPerm(t *testing.T) {
seed := uint64(12345)
p := Perm(seed, 100)
if len(p) != 100 {
t.Errorf("got %v; want 100", len(p))
}
expect := [][]int{
{5, 7, 1, 4, 0, 9, 2, 3, 6, 8},
{0, 5, 9, 8, 1, 6, 2, 4, 3, 7},
{5, 2, 3, 1, 9, 7, 6, 8, 4, 0},
{4, 5, 7, 1, 6, 3, 8, 2, 0, 9},
{5, 7, 0, 9, 2, 1, 8, 4, 6, 3},
}
for i := range 5 {
got := Perm(seed+uint64(i), 10)
want := expect[i]
if !slices.Equal(got, want) {
t.Errorf("got %v; want %v", got, want)
}
}
}
func TestShuffle(t *testing.T) {
seed := uint64(12345)
p := Perm(seed, 10)
if len(p) != 10 {
t.Errorf("got %v; want 10", len(p))
}
expect := [][]int{
{9, 3, 7, 0, 5, 8, 1, 4, 2, 6},
{9, 8, 6, 2, 3, 1, 7, 5, 0, 4},
{1, 6, 2, 8, 4, 5, 7, 0, 3, 9},
{4, 5, 0, 6, 7, 8, 3, 2, 1, 9},
{8, 2, 4, 9, 0, 5, 1, 7, 3, 6},
}
for i := range 5 {
Shuffle(seed+uint64(i), p)
want := expect[i]
if !slices.Equal(p, want) {
t.Errorf("got %v; want %v", p, want)
}
}
}