// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime_test
import (
"fmt"
"math"
"math/rand"
. "runtime"
"strings"
"testing"
"unsafe"
)
func TestMemHash32Equality(t *testing.T) {
if *UseAeshash {
t.Skip("skipping since AES hash implementation is used")
}
var b [4]byte
r := rand.New(rand.NewSource(1234))
seed := uintptr(r.Uint64())
for i := 0; i < 100; i++ {
randBytes(r, b[:])
got := MemHash32(unsafe.Pointer(&b), seed)
want := MemHash(unsafe.Pointer(&b), seed, 4)
if got != want {
t.Errorf("MemHash32(%x, %v) = %v; want %v", b, seed, got, want)
}
}
}
func TestMemHash64Equality(t *testing.T) {
if *UseAeshash {
t.Skip("skipping since AES hash implementation is used")
}
var b [8]byte
r := rand.New(rand.NewSource(1234))
seed := uintptr(r.Uint64())
for i := 0; i < 100; i++ {
randBytes(r, b[:])
got := MemHash64(unsafe.Pointer(&b), seed)
want := MemHash(unsafe.Pointer(&b), seed, 8)
if got != want {
t.Errorf("MemHash64(%x, %v) = %v; want %v", b, seed, got, want)
}
}
}
// Smhasher is a torture test for hash functions.
// https://code.google.com/p/smhasher/
// This code is a port of some of the Smhasher tests to Go.
//
// The current AES hash function passes Smhasher. Our fallback
// hash functions don't, so we only enable the difficult tests when
// we know the AES implementation is available.
// Sanity checks.
// hash should not depend on values outside key.
// hash should not depend on alignment.
func TestSmhasherSanity(t *testing.T) {
r := rand.New(rand.NewSource(1234))
const REP = 10
const KEYMAX = 128
const PAD = 16
const OFFMAX = 16
for k := 0; k < REP; k++ {
for n := 0; n < KEYMAX; n++ {
for i := 0; i < OFFMAX; i++ {
var b [KEYMAX + OFFMAX + 2*PAD]byte
var c [KEYMAX + OFFMAX + 2*PAD]byte
randBytes(r, b[:])
randBytes(r, c[:])
copy(c[PAD+i:PAD+i+n], b[PAD:PAD+n])
if BytesHash(b[PAD:PAD+n], 0) != BytesHash(c[PAD+i:PAD+i+n], 0) {
t.Errorf("hash depends on bytes outside key")
}
}
}
}
}
type HashSet struct {
m map[uintptr]struct{} // set of hashes added
n int // number of hashes added
}
func newHashSet() *HashSet {
return &HashSet{make(map[uintptr]struct{}), 0}
}
func (s *HashSet) add(h uintptr) {
s.m[h] = struct{}{}
s.n++
}
func (s *HashSet) addS(x string) {
s.add(StringHash(x, 0))
}
func (s *HashSet) addB(x []byte) {
s.add(BytesHash(x, 0))
}
func (s *HashSet) addS_seed(x string, seed uintptr) {
s.add(StringHash(x, seed))
}
func (s *HashSet) check(t *testing.T) {
const SLOP = 10.0
collisions := s.n - len(s.m)
//fmt.Printf("%d/%d\n", len(s.m), s.n)
pairs := int64(s.n) * int64(s.n-1) / 2
expected := float64(pairs) / math.Pow(2.0, float64(hashSize))
stddev := math.Sqrt(expected)
if float64(collisions) > expected+SLOP*(3*stddev+1) {
t.Errorf("unexpected number of collisions: got=%d mean=%f stddev=%f", collisions, expected, stddev)
}
}
// a string plus adding zeros must make distinct hashes
func TestSmhasherAppendedZeros(t *testing.T) {
s := "hello" + strings.Repeat("\x00", 256)
h := newHashSet()
for i := 0; i <= len(s); i++ {
h.addS(s[:i])
}
h.check(t)
}
// All 0-3 byte strings have distinct hashes.
func TestSmhasherSmallKeys(t *testing.T) {
h := newHashSet()
var b [3]byte
for i := 0; i < 256; i++ {
b[0] = byte(i)
h.addB(b[:1])
for j := 0; j < 256; j++ {
b[1] = byte(j)
h.addB(b[:2])
if !testing.Short() {
for k := 0; k < 256; k++ {
b[2] = byte(k)
h.addB(b[:3])
}
}
}
}
h.check(t)
}
// Different length strings of all zeros have distinct hashes.
func TestSmhasherZeros(t *testing.T) {
N := 256 * 1024
if testing.Short() {
N = 1024
}
h := newHashSet()
b := make([]byte, N)
for i := 0; i <= N; i++ {
h.addB(b[:i])
}
h.check(t)
}
// Strings with up to two nonzero bytes all have distinct hashes.
func TestSmhasherTwoNonzero(t *testing.T) {
if GOARCH == "wasm" {
t.Skip("Too slow on wasm")
}
if testing.Short() {
t.Skip("Skipping in short mode")
}
h := newHashSet()
for n := 2; n <= 16; n++ {
twoNonZero(h, n)
}
h.check(t)
}
func twoNonZero(h *HashSet, n int) {
b := make([]byte, n)
// all zero
h.addB(b)
// one non-zero byte
for i := 0; i < n; i++ {
for x := 1; x < 256; x++ {
b[i] = byte(x)
h.addB(b)
b[i] = 0
}
}
// two non-zero bytes
for i := 0; i < n; i++ {
for x := 1; x < 256; x++ {
b[i] = byte(x)
for j := i + 1; j < n; j++ {
for y := 1; y < 256; y++ {
b[j] = byte(y)
h.addB(b)
b[j] = 0
}
}
b[i] = 0
}
}
}
// Test strings with repeats, like "abcdabcdabcdabcd..."
func TestSmhasherCyclic(t *testing.T) {
if testing.Short() {
t.Skip("Skipping in short mode")
}
r := rand.New(rand.NewSource(1234))
const REPEAT = 8
const N = 1000000
for n := 4; n <= 12; n++ {
h := newHashSet()
b := make([]byte, REPEAT*n)
for i := 0; i < N; i++ {
b[0] = byte(i * 79 % 97)
b[1] = byte(i * 43 % 137)
b[2] = byte(i * 151 % 197)
b[3] = byte(i * 199 % 251)
randBytes(r, b[4:n])
for j := n; j < n*REPEAT; j++ {
b[j] = b[j-n]
}
h.addB(b)
}
h.check(t)
}
}
// Test strings with only a few bits set
func TestSmhasherSparse(t *testing.T) {
if GOARCH == "wasm" {
t.Skip("Too slow on wasm")
}
if testing.Short() {
t.Skip("Skipping in short mode")
}
sparse(t, 32, 6)
sparse(t, 40, 6)
sparse(t, 48, 5)
sparse(t, 56, 5)
sparse(t, 64, 5)
sparse(t, 96, 4)
sparse(t, 256, 3)
sparse(t, 2048, 2)
}
func sparse(t *testing.T, n int, k int) {
b := make([]byte, n/8)
h := newHashSet()
setbits(h, b, 0, k)
h.check(t)
}
// set up to k bits at index i and greater
func setbits(h *HashSet, b []byte, i int, k int) {
h.addB(b)
if k == 0 {
return
}
for j := i; j < len(b)*8; j++ {
b[j/8] |= byte(1 << uint(j&7))
setbits(h, b, j+1, k-1)
b[j/8] &= byte(^(1 << uint(j&7)))
}
}
// Test all possible combinations of n blocks from the set s.
// "permutation" is a bad name here, but it is what Smhasher uses.
func TestSmhasherPermutation(t *testing.T) {
if GOARCH == "wasm" {
t.Skip("Too slow on wasm")
}
if testing.Short() {
t.Skip("Skipping in short mode")
}
permutation(t, []uint32{0, 1, 2, 3, 4, 5, 6, 7}, 8)
permutation(t, []uint32{0, 1 << 29, 2 << 29, 3 << 29, 4 << 29, 5 << 29, 6 << 29, 7 << 29}, 8)
permutation(t, []uint32{0, 1}, 20)
permutation(t, []uint32{0, 1 << 31}, 20)
permutation(t, []uint32{0, 1, 2, 3, 4, 5, 6, 7, 1 << 29, 2 << 29, 3 << 29, 4 << 29, 5 << 29, 6 << 29, 7 << 29}, 6)
}
func permutation(t *testing.T, s []uint32, n int) {
b := make([]byte, n*4)
h := newHashSet()
genPerm(h, b, s, 0)
h.check(t)
}
func genPerm(h *HashSet, b []byte, s []uint32, n int) {
h.addB(b[:n])
if n == len(b) {
return
}
for _, v := range s {
b[n] = byte(v)
b[n+1] = byte(v >> 8)
b[n+2] = byte(v >> 16)
b[n+3] = byte(v >> 24)
genPerm(h, b, s, n+4)
}
}
type Key interface {
clear() // set bits all to 0
random(r *rand.Rand) // set key to something random
bits() int // how many bits key has
flipBit(i int) // flip bit i of the key
hash() uintptr // hash the key
name() string // for error reporting
}
type BytesKey struct {
b []byte
}
func (k *BytesKey) clear() {
for i := range k.b {
k.b[i] = 0
}
}
func (k *BytesKey) random(r *rand.Rand) {
randBytes(r, k.b)
}
func (k *BytesKey) bits() int {
return len(k.b) * 8
}
func (k *BytesKey) flipBit(i int) {
k.b[i>>3] ^= byte(1 << uint(i&7))
}
func (k *BytesKey) hash() uintptr {
return BytesHash(k.b, 0)
}
func (k *BytesKey) name() string {
return fmt.Sprintf("bytes%d", len(k.b))
}
type Int32Key struct {
i uint32
}
func (k *Int32Key) clear() {
k.i = 0
}
func (k *Int32Key) random(r *rand.Rand) {
k.i = r.Uint32()
}
func (k *Int32Key) bits() int {
return 32
}
func (k *Int32Key) flipBit(i int) {
k.i ^= 1 << uint(i)
}
func (k *Int32Key) hash() uintptr {
return Int32Hash(k.i, 0)
}
func (k *Int32Key) name() string {
return "int32"
}
type Int64Key struct {
i uint64
}
func (k *Int64Key) clear() {
k.i = 0
}
func (k *Int64Key) random(r *rand.Rand) {
k.i = uint64(r.Uint32()) + uint64(r.Uint32())<<32
}
func (k *Int64Key) bits() int {
return 64
}
func (k *Int64Key) flipBit(i int) {
k.i ^= 1 << uint(i)
}
func (k *Int64Key) hash() uintptr {
return Int64Hash(k.i, 0)
}
func (k *Int64Key) name() string {
return "int64"
}
type EfaceKey struct {
i interface{}
}
func (k *EfaceKey) clear() {
k.i = nil
}
func (k *EfaceKey) random(r *rand.Rand) {
k.i = uint64(r.Int63())
}
func (k *EfaceKey) bits() int {
// use 64 bits. This tests inlined interfaces
// on 64-bit targets and indirect interfaces on
// 32-bit targets.
return 64
}
func (k *EfaceKey) flipBit(i int) {
k.i = k.i.(uint64) ^ uint64(1)<<uint(i)
}
func (k *EfaceKey) hash() uintptr {
return EfaceHash(k.i, 0)
}
func (k *EfaceKey) name() string {
return "Eface"
}
type IfaceKey struct {
i interface {
F()
}
}
type fInter uint64
func (x fInter) F() {
}
func (k *IfaceKey) clear() {
k.i = nil
}
func (k *IfaceKey) random(r *rand.Rand) {
k.i = fInter(r.Int63())
}
func (k *IfaceKey) bits() int {
// use 64 bits. This tests inlined interfaces
// on 64-bit targets and indirect interfaces on
// 32-bit targets.
return 64
}
func (k *IfaceKey) flipBit(i int) {
k.i = k.i.(fInter) ^ fInter(1)<<uint(i)
}
func (k *IfaceKey) hash() uintptr {
return IfaceHash(k.i, 0)
}
func (k *IfaceKey) name() string {
return "Iface"
}
// Flipping a single bit of a key should flip each output bit with 50% probability.
func TestSmhasherAvalanche(t *testing.T) {
if GOARCH == "wasm" {
t.Skip("Too slow on wasm")
}
if testing.Short() {
t.Skip("Skipping in short mode")
}
avalancheTest1(t, &BytesKey{make([]byte, 2)})
avalancheTest1(t, &BytesKey{make([]byte, 4)})
avalancheTest1(t, &BytesKey{make([]byte, 8)})
avalancheTest1(t, &BytesKey{make([]byte, 16)})
avalancheTest1(t, &BytesKey{make([]byte, 32)})
avalancheTest1(t, &BytesKey{make([]byte, 200)})
avalancheTest1(t, &Int32Key{})
avalancheTest1(t, &Int64Key{})
avalancheTest1(t, &EfaceKey{})
avalancheTest1(t, &IfaceKey{})
}
func avalancheTest1(t *testing.T, k Key) {
const REP = 100000
r := rand.New(rand.NewSource(1234))
n := k.bits()
// grid[i][j] is a count of whether flipping
// input bit i affects output bit j.
grid := make([][hashSize]int, n)
for z := 0; z < REP; z++ {
// pick a random key, hash it
k.random(r)
h := k.hash()
// flip each bit, hash & compare the results
for i := 0; i < n; i++ {
k.flipBit(i)
d := h ^ k.hash()
k.flipBit(i)
// record the effects of that bit flip
g := &grid[i]
for j := 0; j < hashSize; j++ {
g[j] += int(d & 1)
d >>= 1
}
}
}
// Each entry in the grid should be about REP/2.
// More precisely, we did N = k.bits() * hashSize experiments where
// each is the sum of REP coin flips. We want to find bounds on the
// sum of coin flips such that a truly random experiment would have
// all sums inside those bounds with 99% probability.
N := n * hashSize
var c float64
// find c such that Prob(mean-c*stddev < x < mean+c*stddev)^N > .9999
for c = 0.0; math.Pow(math.Erf(c/math.Sqrt(2)), float64(N)) < .9999; c += .1 {
}
c *= 4.0 // allowed slack - we don't need to be perfectly random
mean := .5 * REP
stddev := .5 * math.Sqrt(REP)
low := int(mean - c*stddev)
high := int(mean + c*stddev)
for i := 0; i < n; i++ {
for j := 0; j < hashSize; j++ {
x := grid[i][j]
if x < low || x > high {
t.Errorf("bad bias for %s bit %d -> bit %d: %d/%d\n", k.name(), i, j, x, REP)
}
}
}
}
// All bit rotations of a set of distinct keys
func TestSmhasherWindowed(t *testing.T) {
windowed(t, &Int32Key{})
windowed(t, &Int64Key{})
windowed(t, &BytesKey{make([]byte, 128)})
}
func windowed(t *testing.T, k Key) {
if GOARCH == "wasm" {
t.Skip("Too slow on wasm")
}
if testing.Short() {
t.Skip("Skipping in short mode")
}
const BITS = 16
for r := 0; r < k.bits(); r++ {
h := newHashSet()
for i := 0; i < 1<<BITS; i++ {
k.clear()
for j := 0; j < BITS; j++ {
if i>>uint(j)&1 != 0 {
k.flipBit((j + r) % k.bits())
}
}
h.add(k.hash())
}
h.check(t)
}
}
// All keys of the form prefix + [A-Za-z0-9]*N + suffix.
func TestSmhasherText(t *testing.T) {
if testing.Short() {
t.Skip("Skipping in short mode")
}
text(t, "Foo", "Bar")
text(t, "FooBar", "")
text(t, "", "FooBar")
}
func text(t *testing.T, prefix, suffix string) {
const N = 4
const S = "ABCDEFGHIJKLMNOPQRSTabcdefghijklmnopqrst0123456789"
const L = len(S)
b := make([]byte, len(prefix)+N+len(suffix))
copy(b, prefix)
copy(b[len(prefix)+N:], suffix)
h := newHashSet()
c := b[len(prefix):]
for i := 0; i < L; i++ {
c[0] = S[i]
for j := 0; j < L; j++ {
c[1] = S[j]
for k := 0; k < L; k++ {
c[2] = S[k]
for x := 0; x < L; x++ {
c[3] = S[x]
h.addB(b)
}
}
}
}
h.check(t)
}
// Make sure different seed values generate different hashes.
func TestSmhasherSeed(t *testing.T) {
h := newHashSet()
const N = 100000
s := "hello"
for i := 0; i < N; i++ {
h.addS_seed(s, uintptr(i))
}
h.check(t)
}
// size of the hash output (32 or 64 bits)
const hashSize = 32 + int(^uintptr(0)>>63<<5)
func randBytes(r *rand.Rand, b []byte) {
for i := range b {
b[i] = byte(r.Uint32())
}
}
func benchmarkHash(b *testing.B, n int) {
s := strings.Repeat("A", n)
for i := 0; i < b.N; i++ {
StringHash(s, 0)
}
b.SetBytes(int64(n))
}
func BenchmarkHash5(b *testing.B) { benchmarkHash(b, 5) }
func BenchmarkHash16(b *testing.B) { benchmarkHash(b, 16) }
func BenchmarkHash64(b *testing.B) { benchmarkHash(b, 64) }
func BenchmarkHash1024(b *testing.B) { benchmarkHash(b, 1024) }
func BenchmarkHash65536(b *testing.B) { benchmarkHash(b, 65536) }
func TestArrayHash(t *testing.T) {
// Make sure that "" in arrays hash correctly. The hash
// should at least scramble the input seed so that, e.g.,
// {"","foo"} and {"foo",""} have different hashes.
// If the hash is bad, then all (8 choose 4) = 70 keys
// have the same hash. If so, we allocate 70/8 = 8
// overflow buckets. If the hash is good we don't
// normally allocate any overflow buckets, and the
// probability of even one or two overflows goes down rapidly.
// (There is always 1 allocation of the bucket array. The map
// header is allocated on the stack.)
f := func() {
// Make the key type at most 128 bytes. Otherwise,
// we get an allocation per key.
type key [8]string
m := make(map[key]bool, 70)
// fill m with keys that have 4 "foo"s and 4 ""s.
for i := 0; i < 256; i++ {
var k key
cnt := 0
for j := uint(0); j < 8; j++ {
if i>>j&1 != 0 {
k[j] = "foo"
cnt++
}
}
if cnt == 4 {
m[k] = true
}
}
if len(m) != 70 {
t.Errorf("bad test: (8 choose 4) should be 70, not %d", len(m))
}
}
if n := testing.AllocsPerRun(10, f); n > 6 {
t.Errorf("too many allocs %f - hash not balanced", n)
}
}
func TestStructHash(t *testing.T) {
// See the comment in TestArrayHash.
f := func() {
type key struct {
a, b, c, d, e, f, g, h string
}
m := make(map[key]bool, 70)
// fill m with keys that have 4 "foo"s and 4 ""s.
for i := 0; i < 256; i++ {
var k key
cnt := 0
if i&1 != 0 {
k.a = "foo"
cnt++
}
if i&2 != 0 {
k.b = "foo"
cnt++
}
if i&4 != 0 {
k.c = "foo"
cnt++
}
if i&8 != 0 {
k.d = "foo"
cnt++
}
if i&16 != 0 {
k.e = "foo"
cnt++
}
if i&32 != 0 {
k.f = "foo"
cnt++
}
if i&64 != 0 {
k.g = "foo"
cnt++
}
if i&128 != 0 {
k.h = "foo"
cnt++
}
if cnt == 4 {
m[k] = true
}
}
if len(m) != 70 {
t.Errorf("bad test: (8 choose 4) should be 70, not %d", len(m))
}
}
if n := testing.AllocsPerRun(10, f); n > 6 {
t.Errorf("too many allocs %f - hash not balanced", n)
}
}
var sink uint64
func BenchmarkAlignedLoad(b *testing.B) {
var buf [16]byte
p := unsafe.Pointer(&buf[0])
var s uint64
for i := 0; i < b.N; i++ {
s += ReadUnaligned64(p)
}
sink = s
}
func BenchmarkUnalignedLoad(b *testing.B) {
var buf [16]byte
p := unsafe.Pointer(&buf[1])
var s uint64
for i := 0; i < b.N; i++ {
s += ReadUnaligned64(p)
}
sink = s
}
func TestCollisions(t *testing.T) {
if testing.Short() {
t.Skip("Skipping in short mode")
}
for i := 0; i < 16; i++ {
for j := 0; j < 16; j++ {
if j == i {
continue
}
var a [16]byte
m := make(map[uint16]struct{}, 1<<16)
for n := 0; n < 1<<16; n++ {
a[i] = byte(n)
a[j] = byte(n >> 8)
m[uint16(BytesHash(a[:], 0))] = struct{}{}
}
if len(m) <= 1<<15 {
t.Errorf("too many collisions i=%d j=%d outputs=%d out of 65536\n", i, j, len(m))
}
}
}
}
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