| // 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" |
| ) |
| |
| // 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 { |
| 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 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") |
| } |
| if !HaveGoodHash() { |
| t.Skip("fallback hash not good enough for this test") |
| } |
| 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 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 testing.Short() { |
| t.Skip("Skipping in short mode") |
| } |
| if !HaveGoodHash() { |
| t.Skip("fallback hash not good enough for this test") |
| } |
| 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" |
| } |
| |
| // Flipping a single bit of a key should flip each output bit with 50% probability. |
| func TestSmhasherAvalanche(t *testing.T) { |
| if !HaveGoodHash() { |
| t.Skip("fallback hash not good enough for this test") |
| } |
| 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{}) |
| } |
| 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 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) } |