Update: faster hash

benchmark_test.go

@@ -70,13 +70,13 @@ func BenchmarkRandomR(b *testing.B) {
 // goarch: amd64
 // pkg: github.com/fufuok/balancer
 // cpu: Intel(R) Xeon(R) CPU E5-2667 v2 @ 3.30GHz
-// BenchmarkWeightedRoundRobin-4 30918976 38.35 ns/op 0 B/op 0 allocs/op
-// BenchmarkWeightedRoundRobin-4 30627727 38.33 ns/op 0 B/op 0 allocs/op
-// BenchmarkSmoothWeightedRoundRobin-4 20629270 59.60 ns/op 0 B/op 0 allocs/op
-// BenchmarkSmoothWeightedRoundRobin-4 21024522 75.05 ns/op 0 B/op 0 allocs/op
-// BenchmarkConsistentHash-4 26980348 43.72 ns/op 0 B/op 0 allocs/op
-// BenchmarkConsistentHash-4 26978271 43.77 ns/op 0 B/op 0 allocs/op
-// BenchmarkRoundRobin-4 51317532 23.18 ns/op 0 B/op 0 allocs/op
-// BenchmarkRoundRobin-4 51717782 29.64 ns/op 0 B/op 0 allocs/op
-// BenchmarkRandomR-4 47053610 32.63 ns/op 0 B/op 0 allocs/op
-// BenchmarkRandomR-4 46210752 25.15 ns/op 0 B/op 0 allocs/op
+// BenchmarkWeightedRoundRobin-4 30947391 37.95 ns/op 0 B/op 0 allocs/op
+// BenchmarkWeightedRoundRobin-4 30508263 48.99 ns/op 0 B/op 0 allocs/op
+// BenchmarkSmoothWeightedRoundRobin-4 20379349 60.12 ns/op 0 B/op 0 allocs/op
+// BenchmarkSmoothWeightedRoundRobin-4 20407590 75.66 ns/op 0 B/op 0 allocs/op
+// BenchmarkConsistentHash-4 33911062 44.45 ns/op 0 B/op 0 allocs/op
+// BenchmarkConsistentHash-4 34818607 44.34 ns/op 0 B/op 0 allocs/op
+// BenchmarkRoundRobin-4 51605906 23.35 ns/op 0 B/op 0 allocs/op
+// BenchmarkRoundRobin-4 50344368 29.87 ns/op 0 B/op 0 allocs/op
+// BenchmarkRandomR-4 45422324 26.06 ns/op 0 B/op 0 allocs/op
+// BenchmarkRandomR-4 46060688 32.93 ns/op 0 B/op 0 allocs/op

hash.go

@@ -1,7 +1,6 @@
 package balancer
 
 import (
- "hash/fnv"
  "sync"
 
  "github.com/fufuok/balancer/internal/utils"
@@ -18,6 +17,12 @@ type consistentHash struct {
  sync.RWMutex
 }
 
+const (
+ // FNVa offset basis. See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash
+ offset64 = 14695981039346656037
+ prime64 = 1099511628211
+)
+
 func NewConsistentHash(items ...[]string) (lb *consistentHash) {
  if len(items) > 0 && len(items[0]) > 0 {
  lb = &consistentHash{}
@@ -71,9 +76,12 @@ func (b *consistentHash) chooseNext(key []string) (choice string) {
 }
 
 func (b *consistentHash) hash(s string) uint64 {
- h := fnv.New64a()
- _, _ = h.Write([]byte(s))
- return h.Sum64()
+ var h uint64 = offset64
+ for i := 0; i < len(s); i++ {
+ h ^= uint64(s[i])
+ h *= prime64
+ }
+ return h
 }
 
 func (b *consistentHash) Remove(item string, asClean ...bool) (ok bool) {