d32f396204
- fixes for SortSliceByValue - fixes for tests
201 lines
4.6 KiB
Go
201 lines
4.6 KiB
Go
// Package hrw implements Rendezvous hashing.
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// http://en.wikipedia.org/wiki/Rendezvous_hashing.
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package hrw
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import (
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"encoding/binary"
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"reflect"
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"sort"
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"github.com/spaolacci/murmur3"
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)
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type (
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swapper func(i, j int)
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// Hasher interface used by SortSliceByValue
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Hasher interface{ Hash() uint64 }
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hashed struct {
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length int
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sorted []uint64
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weight []uint64
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}
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)
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func weight(x uint64, y uint64) uint64 {
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acc := x ^ y
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// here used mmh3 64 bit finalizer
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// https://github.com/aappleby/smhasher/blob/61a0530f28277f2e850bfc39600ce61d02b518de/src/MurmurHash3.cpp#L81
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acc ^= acc >> 33
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acc = acc * 0xff51afd7ed558ccd
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acc ^= acc >> 33
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acc = acc * 0xc4ceb9fe1a85ec53
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acc ^= acc >> 33
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return acc
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}
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func (h hashed) Len() int { return h.length }
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func (h hashed) Less(i, j int) bool { return h.weight[h.sorted[i]] < h.weight[h.sorted[j]] }
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func (h hashed) Swap(i, j int) { h.sorted[i], h.sorted[j] = h.sorted[j], h.sorted[i] }
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// Hash uses murmur3 hash to return uint64
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func Hash(key []byte) uint64 {
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return murmur3.Sum64(key)
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}
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// SortByWeight receive nodes and hash, and sort it by weight
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func SortByWeight(nodes []uint64, hash uint64) []uint64 {
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var (
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l = len(nodes)
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h = hashed{
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length: l,
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sorted: make([]uint64, 0, l),
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weight: make([]uint64, 0, l),
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}
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)
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for i, node := range nodes {
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h.sorted = append(h.sorted, uint64(i))
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h.weight = append(h.weight, weight(node, hash))
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}
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sort.Sort(h)
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return h.sorted
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}
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// SortSliceByValue received []T and hash to sort by value-weight
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func SortSliceByValue(slice interface{}, hash uint64) {
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t := reflect.TypeOf(slice)
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if t.Kind() != reflect.Slice {
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return
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}
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var (
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val = reflect.ValueOf(slice)
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swap = reflect.Swapper(slice)
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length = val.Len()
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rule = make([]uint64, 0, length)
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)
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if length == 0 {
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return
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}
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switch slice := slice.(type) {
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case []int:
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var key = make([]byte, 16)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint64(key, uint64(slice[i]))
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rule = append(rule, Hash(key))
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}
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case []uint:
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var key = make([]byte, 16)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint64(key, uint64(slice[i]))
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rule = append(rule, Hash(key))
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}
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case []int8:
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for i := 0; i < length; i++ {
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key := byte(slice[i])
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rule = append(rule, Hash([]byte{key}))
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}
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case []uint8:
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for i := 0; i < length; i++ {
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key := slice[i]
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rule = append(rule, Hash([]byte{key}))
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}
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case []int16:
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var key = make([]byte, 8)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint16(key, uint16(slice[i]))
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rule = append(rule, Hash(key))
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}
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case []uint16:
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var key = make([]byte, 8)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint16(key, slice[i])
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rule = append(rule, Hash(key))
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}
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case []int32:
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var key = make([]byte, 16)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint32(key, uint32(slice[i]))
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rule = append(rule, Hash(key))
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}
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case []uint32:
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var key = make([]byte, 16)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint32(key, slice[i])
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rule = append(rule, Hash(key))
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}
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case []int64:
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var key = make([]byte, 32)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint64(key, uint64(slice[i]))
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rule = append(rule, Hash(key))
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}
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case []uint64:
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var key = make([]byte, 32)
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for i := 0; i < length; i++ {
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binary.BigEndian.PutUint64(key, slice[i])
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rule = append(rule, Hash(key))
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}
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case []string:
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for i := 0; i < length; i++ {
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rule = append(rule, Hash([]byte(slice[i])))
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}
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default:
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if _, ok := val.Index(0).Interface().(Hasher); !ok {
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return
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}
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for i := 0; i < length; i++ {
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h := val.Index(i).Interface().(Hasher)
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rule = append(rule, h.Hash())
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}
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}
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rule = SortByWeight(rule, hash)
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sortByRuleInverse(swap, uint64(length), rule)
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}
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// SortSliceByIndex received []T and hash to sort by index-weight
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func SortSliceByIndex(slice interface{}, hash uint64) {
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length := uint64(reflect.ValueOf(slice).Len())
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swap := reflect.Swapper(slice)
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rule := make([]uint64, 0, length)
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for i := uint64(0); i < length; i++ {
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rule = append(rule, i)
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}
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rule = SortByWeight(rule, hash)
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sortByRuleInverse(swap, length, rule)
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}
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func sortByRuleDirect(swap swapper, length uint64, rule []uint64) {
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done := make([]bool, length)
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for i := uint64(0); i < length; i++ {
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if done[i] {
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continue
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}
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for j := rule[i]; !done[rule[j]]; j = rule[j] {
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swap(int(i), int(j))
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done[j] = true
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}
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}
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}
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func sortByRuleInverse(swap swapper, length uint64, rule []uint64) {
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done := make([]bool, length)
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for i := uint64(0); i < length; i++ {
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if done[i] {
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continue
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}
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for j := i; !done[rule[j]]; j = rule[j] {
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swap(int(j), int(rule[j]))
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done[j] = true
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}
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}
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}
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