306 lines
6.3 KiB
Go
306 lines
6.3 KiB
Go
package hrw
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import (
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"encoding/binary"
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"fmt"
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"hash/fnv"
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"reflect"
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"strconv"
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"testing"
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"github.com/reusee/mmh3"
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)
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type hashString string
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var testKey = []byte("Golang simple HRW implementation")
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func Example() {
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// given a set of servers
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servers := []string{
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"one.example.com",
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"two.example.com",
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"three.example.com",
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"four.example.com",
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"five.example.com",
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"six.example.com",
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}
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// HRW can consistently select a uniformly-distributed set of servers for
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// any given key
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var (
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key = []byte("/examples/object-key")
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h = hash(key)
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err = SortSliceByValue(servers, h)
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)
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if err != nil {
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panic(err)
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}
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for id := range servers {
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fmt.Printf("trying GET %s%s\n", servers[id], key)
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}
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// Output:
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// trying GET six.example.com/examples/object-key
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// trying GET one.example.com/examples/object-key
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// trying GET three.example.com/examples/object-key
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// trying GET four.example.com/examples/object-key
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// trying GET five.example.com/examples/object-key
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// trying GET two.example.com/examples/object-key
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}
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func (h hashString) Hash() uint64 {
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hs := fnv.New64()
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// error always nil
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_, _ = hs.Write([]byte(h))
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return (hs.Sum64() >> 1) % m64
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}
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func hash(key []byte) uint64 {
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h := fnv.New64()
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// error always nil
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_, _ = h.Write(key)
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return (h.Sum64() >> 1) ^ m64
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}
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func mur3hash(key []byte) uint64 {
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h := mmh3.New128()
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// error always nil
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_, _ = h.Write(key)
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var (
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data = h.Sum(nil)
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length = len(data)
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result uint64
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)
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for i := 0; i < length; i++ {
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result += uint64(data[i]) << uint64(length-i)
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}
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return result
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}
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func TestSortSliceByIndex(t *testing.T) {
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actual := []string{"a", "b", "c", "d", "e", "f"}
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expect := []string{"e", "a", "c", "d", "b", "f"}
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hash := hash(testKey)
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SortSliceByIndex(actual, hash)
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if !reflect.DeepEqual(actual, expect) {
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t.Errorf("Was %#v, but expected %#v", actual, expect)
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}
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}
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func TestSortSliceByValue(t *testing.T) {
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actual := []string{"a", "b", "c", "d", "e", "f"}
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expect := []string{"e", "b", "c", "d", "f", "a"}
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err != nil {
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t.Fatal(err)
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}
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if !reflect.DeepEqual(actual, expect) {
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t.Errorf("Was %#v, but expected %#v", actual, expect)
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}
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}
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func TestSortSliceByValueFail(t *testing.T) {
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t.Run("empty slice", func(t *testing.T) {
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actual := make([]int, 0)
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err != nil {
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t.Fatal(err)
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}
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})
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t.Run("must be slice", func(t *testing.T) {
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actual := 10
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err == nil {
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t.Fatal("must fail for bad type")
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}
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})
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t.Run("must fail for unknown type", func(t *testing.T) {
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actual := []byte{1, 2, 3, 4, 5}
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err == nil {
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t.Fatal("must fail for bad type")
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}
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})
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}
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func TestSortSliceByValueHasher(t *testing.T) {
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actual := []hashString{"a", "b", "c", "d", "e", "f"}
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expect := []hashString{"e", "d", "c", "a", "b", "f"}
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err != nil {
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t.Fatal(err)
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}
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if !reflect.DeepEqual(actual, expect) {
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t.Errorf("Was %#v, but expected %#v", actual, expect)
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}
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}
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func TestSortSliceByValueIntSlice(t *testing.T) {
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actual := []int{0, 1, 2, 3, 4, 5}
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expect := []int{2, 0, 5, 3, 4, 1}
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hash := hash(testKey)
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if err := SortSliceByValue(actual, hash); err != nil {
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t.Fatal(err)
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}
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if !reflect.DeepEqual(actual, expect) {
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t.Errorf("Was %#v, but expected %#v", actual, expect)
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}
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}
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func TestSortByWeight(t *testing.T) {
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nodes := []uint64{1, 2, 3, 4, 5}
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hash := mur3hash(testKey)
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actual := SortByWeight(nodes, hash)
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expected := []uint64{0, 1, 4, 2, 3}
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if !reflect.DeepEqual(actual, expected) {
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t.Errorf("Was %#v, but expected %#v", actual, expected)
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}
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}
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func TestUniformDistribution(t *testing.T) {
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var (
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i uint64
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size = uint64(4)
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nodes = make([]uint64, 0, size)
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counts = make(map[uint64]uint64)
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key = make([]byte, 16)
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keys = uint64(10000000)
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)
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for i = 0; i < size; i++ {
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nodes = append(nodes, i)
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}
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for i = 0; i < keys; i++ {
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binary.BigEndian.PutUint64(key, i)
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hash := hash(key)
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counts[SortByWeight(nodes, hash)[0]]++
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}
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mean := float64(keys) / float64(len(nodes))
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delta := mean * 0.002 // 0.2%
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for node, count := range counts {
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d := mean - float64(count)
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if d > delta || (0-d) > delta {
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t.Errorf(
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"Node %d received %d keys, expected %v (+/- %v)",
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node, count, mean, delta,
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)
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}
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}
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}
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func BenchmarkSortByWeight_fnv_10(b *testing.B) {
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hash := hash(testKey)
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_ = benchmarkSortByWeight(b, 10, hash)
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}
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func BenchmarkSortByWeight_fnv_100(b *testing.B) {
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hash := hash(testKey)
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_ = benchmarkSortByWeight(b, 100, hash)
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}
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func BenchmarkSortByWeight_fnv_1000(b *testing.B) {
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hash := hash(testKey)
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_ = benchmarkSortByWeight(b, 1000, hash)
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}
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func BenchmarkSortByIndex_fnv_10(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByIndex(b, 10, hash)
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}
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func BenchmarkSortByIndex_fnv_100(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByIndex(b, 100, hash)
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}
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func BenchmarkSortByIndex_fnv_1000(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByIndex(b, 1000, hash)
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}
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func BenchmarkSortByValue_fnv_10(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByValue(b, 10, hash)
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}
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func BenchmarkSortByValue_fnv_100(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByValue(b, 100, hash)
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}
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func BenchmarkSortByValue_fnv_1000(b *testing.B) {
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hash := hash(testKey)
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benchmarkSortByValue(b, 1000, hash)
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}
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func benchmarkSortByWeight(b *testing.B, n int, hash uint64) uint64 {
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servers := make([]uint64, n)
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for i := uint64(0); i < uint64(len(servers)); i++ {
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servers[i] = i
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}
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b.ResetTimer()
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b.ReportAllocs()
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var x uint64
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for i := 0; i < b.N; i++ {
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x += SortByWeight(servers, hash)[0]
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}
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return x
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}
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func benchmarkSortByIndex(b *testing.B, n int, hash uint64) {
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servers := make([]uint64, n)
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for i := uint64(0); i < uint64(len(servers)); i++ {
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servers[i] = i
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}
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b.ResetTimer()
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b.ReportAllocs()
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for i := 0; i < b.N; i++ {
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SortSliceByIndex(servers, hash)
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}
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}
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func benchmarkSortByValue(b *testing.B, n int, hash uint64) {
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servers := make([]string, n)
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for i := uint64(0); i < uint64(len(servers)); i++ {
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servers[i] = "localhost:" + strconv.FormatUint(60000-i, 10)
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}
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b.ResetTimer()
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b.ReportAllocs()
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for i := 0; i < b.N; i++ {
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if err := SortSliceByValue(servers, hash); err != nil {
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b.Fatal(err)
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}
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}
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}
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