Fast int64 -> int64 hash in golang.

intintmap

import "github.com/brentp/intintmap"

Package intintmap is a fast int64 key -> int64 value map.

It is copied nearly verbatim from http://java-performance.info/implementing-world-fastest-java-int-to-int-hash-map/ .

It interleaves keys and values in the same underlying array to improve locality.

It is 2-5X faster than the builtin map:

BenchmarkIntIntMapFill                 	      10	 158436598 ns/op
BenchmarkStdMapFill                    	       5	 312135474 ns/op
BenchmarkIntIntMapGet10PercentHitRate  	    5000	    243108 ns/op
BenchmarkStdMapGet10PercentHitRate     	    5000	    268927 ns/op
BenchmarkIntIntMapGet100PercentHitRate 	     500	   2249349 ns/op
BenchmarkStdMapGet100PercentHitRate    	     100	  10258929 ns/op

Usage

m := intintmap.New(32768, 0.6)
m.Put(int64(1234), int64(-222))
m.Put(int64(123), int64(33))

v, ok := m.Get(int64(222))
v, ok := m.Get(int64(333))

m.Del(int64(222))
m.Del(int64(333))

fmt.Println(m.Size())

for k := range m.Keys() {
    fmt.Printf("key: %d\n", k)
}

for kv := range m.Items() {
    fmt.Printf("key: %d, value: %d\n", kv[0], kv[1])
}

type Map

type Map struct {
}

Map is a map-like data-structure for int64s

func New

func New(size int, fillFactor float64) *Map

New returns a map initialized with n spaces and uses the stated fillFactor. The map will grow as needed.

func (*Map) Get

func (m *Map) Get(key int64) (int64, bool)

Get returns the value if the key is found.

func (*Map) Put

func (m *Map) Put(key int64, val int64)

Put adds or updates key with value val.

func (*Map) Del

func (m *Map) Del(key int64)

Del deletes a key and its value.

func (*Map) Keys

func (m *Map) Keys() chan int64

Keys returns a channel for iterating all keys.

func (*Map) Items

func (m *Map) Items() chan [2]int64

Items returns a channel for iterating all key-value pairs.

func (*Map) Size

func (m *Map) Size() int

Size returns size of the map.