libstdc++: Avoid -Wmaybe-uninitialized warnings in text_encoding.cc

[official-gcc.git] / libgo / go / runtime / hash_test.go

// 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 = 50.0
        collisions := s.n - len(s.m)
        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 threshold=%f", collisions, expected, stddev, expected+SLOP*(3*stddev+1))
        }
}

// 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 any
}

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) {
        t.Logf("32 bit keys")
        windowed(t, &Int32Key{})
        t.Logf("64 bit keys")
        windowed(t, &Int64Key{})
        t.Logf("string keys")
        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) {
        if Compiler == "gccgo" {
                t.Skip("does not work on gccgo without better escape analysis")
        }

        // 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))
                        }
                }
        }
}