src/runtime/map_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"
	"reflect"
	"runtime"
	"sort"
	"strings"
	"sync"
	"testing"
)

// negative zero is a good test because:
//  1) 0 and -0 are equal, yet have distinct representations.
//  2) 0 is represented as all zeros, -0 isn't.
// I'm not sure the language spec actually requires this behavior,
// but it's what the current map implementation does.
func TestNegativeZero(t *testing.T) {
	m := make(map[float64]bool, 0)

	m[+0.0] = true
	m[math.Copysign(0.0, -1.0)] = true // should overwrite +0 entry

	if len(m) != 1 {
		t.Error("length wrong")
	}

	for k := range m {
		if math.Copysign(1.0, k) > 0 {
			t.Error("wrong sign")
		}
	}

	m = make(map[float64]bool, 0)
	m[math.Copysign(0.0, -1.0)] = true
	m[+0.0] = true // should overwrite -0.0 entry

	if len(m) != 1 {
		t.Error("length wrong")
	}

	for k := range m {
		if math.Copysign(1.0, k) < 0 {
			t.Error("wrong sign")
		}
	}
}

// nan is a good test because nan != nan, and nan has
// a randomized hash value.
func TestNan(t *testing.T) {
	m := make(map[float64]int, 0)
	nan := math.NaN()
	m[nan] = 1
	m[nan] = 2
	m[nan] = 4
	if len(m) != 3 {
		t.Error("length wrong")
	}
	s := 0
	for k, v := range m {
		if k == k {
			t.Error("nan disappeared")
		}
		if (v & (v - 1)) != 0 {
			t.Error("value wrong")
		}
		s |= v
	}
	if s != 7 {
		t.Error("values wrong")
	}
}

// Maps aren't actually copied on assignment.
func TestAlias(t *testing.T) {
	m := make(map[int]int, 0)
	m[0] = 5
	n := m
	n[0] = 6
	if m[0] != 6 {
		t.Error("alias didn't work")
	}
}

func TestGrowWithNaN(t *testing.T) {
	m := make(map[float64]int, 4)
	nan := math.NaN()
	m[nan] = 1
	m[nan] = 2
	m[nan] = 4
	cnt := 0
	s := 0
	growflag := true
	for k, v := range m {
		if growflag {
			// force a hashtable resize
			for i := 0; i < 100; i++ {
				m[float64(i)] = i
			}
			growflag = false
		}
		if k != k {
			cnt++
			s |= v
		}
	}
	if cnt != 3 {
		t.Error("NaN keys lost during grow")
	}
	if s != 7 {
		t.Error("NaN values lost during grow")
	}
}

type FloatInt struct {
	x float64
	y int
}

func TestGrowWithNegativeZero(t *testing.T) {
	negzero := math.Copysign(0.0, -1.0)
	m := make(map[FloatInt]int, 4)
	m[FloatInt{0.0, 0}] = 1
	m[FloatInt{0.0, 1}] = 2
	m[FloatInt{0.0, 2}] = 4
	m[FloatInt{0.0, 3}] = 8
	growflag := true
	s := 0
	cnt := 0
	negcnt := 0
	// The first iteration should return the +0 key.
	// The subsequent iterations should return the -0 key.
	// I'm not really sure this is required by the spec,
	// but it makes sense.
	// TODO: are we allowed to get the first entry returned again???
	for k, v := range m {
		if v == 0 {
			continue
		} // ignore entries added to grow table
		cnt++
		if math.Copysign(1.0, k.x) < 0 {
			if v&16 == 0 {
				t.Error("key/value not updated together 1")
			}
			negcnt++
			s |= v & 15
		} else {
			if v&16 == 16 {
				t.Error("key/value not updated together 2", k, v)
			}
			s |= v
		}
		if growflag {
			// force a hashtable resize
			for i := 0; i < 100; i++ {
				m[FloatInt{3.0, i}] = 0
			}
			// then change all the entries
			// to negative zero
			m[FloatInt{negzero, 0}] = 1 | 16
			m[FloatInt{negzero, 1}] = 2 | 16
			m[FloatInt{negzero, 2}] = 4 | 16
			m[FloatInt{negzero, 3}] = 8 | 16
			growflag = false
		}
	}
	if s != 15 {
		t.Error("entry missing", s)
	}
	if cnt != 4 {
		t.Error("wrong number of entries returned by iterator", cnt)
	}
	if negcnt != 3 {
		t.Error("update to negzero missed by iteration", negcnt)
	}
}

func TestIterGrowAndDelete(t *testing.T) {
	m := make(map[int]int, 4)
	for i := 0; i < 100; i++ {
		m[i] = i
	}
	growflag := true
	for k := range m {
		if growflag {
			// grow the table
			for i := 100; i < 1000; i++ {
				m[i] = i
			}
			// delete all odd keys
			for i := 1; i < 1000; i += 2 {
				delete(m, i)
			}
			growflag = false
		} else {
			if k&1 == 1 {
				t.Error("odd value returned")
			}
		}
	}
}

// make sure old bucket arrays don't get GCd while
// an iterator is still using them.
func TestIterGrowWithGC(t *testing.T) {
	m := make(map[int]int, 4)
	for i := 0; i < 16; i++ {
		m[i] = i
	}
	growflag := true
	bitmask := 0
	for k := range m {
		if k < 16 {
			bitmask |= 1 << uint(k)
		}
		if growflag {
			// grow the table
			for i := 100; i < 1000; i++ {
				m[i] = i
			}
			// trigger a gc
			runtime.GC()
			growflag = false
		}
	}
	if bitmask != 1<<16-1 {
		t.Error("missing key", bitmask)
	}
}

func testConcurrentReadsAfterGrowth(t *testing.T, useReflect bool) {
	if runtime.GOMAXPROCS(-1) == 1 {
		defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(16))
	}
	numLoop := 10
	numGrowStep := 250
	numReader := 16
	if testing.Short() {
		numLoop, numGrowStep = 2, 500
	}
	for i := 0; i < numLoop; i++ {
		m := make(map[int]int, 0)
		for gs := 0; gs < numGrowStep; gs++ {
			m[gs] = gs
			var wg sync.WaitGroup
			wg.Add(numReader * 2)
			for nr := 0; nr < numReader; nr++ {
				go func() {
					defer wg.Done()
					for range m {
					}
				}()
				go func() {
					defer wg.Done()
					for key := 0; key < gs; key++ {
						_ = m[key]
					}
				}()
				if useReflect {
					wg.Add(1)
					go func() {
						defer wg.Done()
						mv := reflect.ValueOf(m)
						keys := mv.MapKeys()
						for _, k := range keys {
							mv.MapIndex(k)
						}
					}()
				}
			}
			wg.Wait()
		}
	}
}

func TestConcurrentReadsAfterGrowth(t *testing.T) {
	testConcurrentReadsAfterGrowth(t, false)
}

func TestConcurrentReadsAfterGrowthReflect(t *testing.T) {
	testConcurrentReadsAfterGrowth(t, true)
}

func TestBigItems(t *testing.T) {
	var key [256]string
	for i := 0; i < 256; i++ {
		key[i] = "foo"
	}
	m := make(map[[256]string][256]string, 4)
	for i := 0; i < 100; i++ {
		key[37] = fmt.Sprintf("string%02d", i)
		m[key] = key
	}
	var keys [100]string
	var values [100]string
	i := 0
	for k, v := range m {
		keys[i] = k[37]
		values[i] = v[37]
		i++
	}
	sort.Strings(keys[:])
	sort.Strings(values[:])
	for i := 0; i < 100; i++ {
		if keys[i] != fmt.Sprintf("string%02d", i) {
			t.Errorf("#%d: missing key: %v", i, keys[i])
		}
		if values[i] != fmt.Sprintf("string%02d", i) {
			t.Errorf("#%d: missing value: %v", i, values[i])
		}
	}
}

type empty struct {
}

func TestEmptyKeyAndValue(t *testing.T) {
	a := make(map[int]empty, 4)
	b := make(map[empty]int, 4)
	c := make(map[empty]empty, 4)
	a[0] = empty{}
	b[empty{}] = 0
	b[empty{}] = 1
	c[empty{}] = empty{}

	if len(a) != 1 {
		t.Errorf("empty value insert problem")
	}
	if b[empty{}] != 1 {
		t.Errorf("empty key returned wrong value")
	}
}

// Tests a map with a single bucket, with same-lengthed short keys
// ("quick keys") as well as long keys.
func TestSingleBucketMapStringKeys_DupLen(t *testing.T) {
	testMapLookups(t, map[string]string{
		"x":    "x1val",
		"xx":   "x2val",
		"foo":  "fooval",
		"bar":  "barval", // same key length as "foo"
		"xxxx": "x4val",
		strings.Repeat("x", 128): "longval1",
		strings.Repeat("y", 128): "longval2",
	})
}

// Tests a map with a single bucket, with all keys having different lengths.
func TestSingleBucketMapStringKeys_NoDupLen(t *testing.T) {
	testMapLookups(t, map[string]string{
		"x":                      "x1val",
		"xx":                     "x2val",
		"foo":                    "fooval",
		"xxxx":                   "x4val",
		"xxxxx":                  "x5val",
		"xxxxxx":                 "x6val",
		strings.Repeat("x", 128): "longval",
	})
}

func testMapLookups(t *testing.T, m map[string]string) {
	for k, v := range m {
		if m[k] != v {
			t.Fatalf("m[%q] = %q; want %q", k, m[k], v)
		}
	}
}

// Tests whether the iterator returns the right elements when
// started in the middle of a grow, when the keys are NaNs.
func TestMapNanGrowIterator(t *testing.T) {
	m := make(map[float64]int)
	nan := math.NaN()
	const nBuckets = 16
	// To fill nBuckets buckets takes LOAD * nBuckets keys.
	nKeys := int(nBuckets * *runtime.HashLoad)

	// Get map to full point with nan keys.
	for i := 0; i < nKeys; i++ {
		m[nan] = i
	}
	// Trigger grow
	m[1.0] = 1
	delete(m, 1.0)

	// Run iterator
	found := make(map[int]struct{})
	for _, v := range m {
		if v != -1 {
			if _, repeat := found[v]; repeat {
				t.Fatalf("repeat of value %d", v)
			}
			found[v] = struct{}{}
		}
		if len(found) == nKeys/2 {
			// Halfway through iteration, finish grow.
			for i := 0; i < nBuckets; i++ {
				delete(m, 1.0)
			}
		}
	}
	if len(found) != nKeys {
		t.Fatalf("missing value")
	}
}

func TestMapIterOrder(t *testing.T) {
	for _, n := range [...]int{3, 7, 9, 15} {
		for i := 0; i < 1000; i++ {
			// Make m be {0: true, 1: true, ..., n-1: true}.
			m := make(map[int]bool)
			for i := 0; i < n; i++ {
				m[i] = true
			}
			// Check that iterating over the map produces at least two different orderings.
			ord := func() []int {
				var s []int
				for key := range m {
					s = append(s, key)
				}
				return s
			}
			first := ord()
			ok := false
			for try := 0; try < 100; try++ {
				if !reflect.DeepEqual(first, ord()) {
					ok = true
					break
				}
			}
			if !ok {
				t.Errorf("Map with n=%d elements had consistent iteration order: %v", n, first)
				break
			}
		}
	}
}

// Issue 8410
func TestMapSparseIterOrder(t *testing.T) {
	// Run several rounds to increase the probability
	// of failure. One is not enough.
NextRound:
	for round := 0; round < 10; round++ {
		m := make(map[int]bool)
		// Add 1000 items, remove 980.
		for i := 0; i < 1000; i++ {
			m[i] = true
		}
		for i := 20; i < 1000; i++ {
			delete(m, i)
		}

		var first []int
		for i := range m {
			first = append(first, i)
		}

		// 800 chances to get a different iteration order.
		// See bug 8736 for why we need so many tries.
		for n := 0; n < 800; n++ {
			idx := 0
			for i := range m {
				if i != first[idx] {
					// iteration order changed.
					continue NextRound
				}
				idx++
			}
		}
		t.Fatalf("constant iteration order on round %d: %v", round, first)
	}
}

func TestMapStringBytesLookup(t *testing.T) {
	// Use large string keys to avoid small-allocation coalescing,
	// which can cause AllocsPerRun to report lower counts than it should.
	m := map[string]int{
		"1000000000000000000000000000000000000000000000000": 1,
		"2000000000000000000000000000000000000000000000000": 2,
	}
	buf := []byte("1000000000000000000000000000000000000000000000000")
	if x := m[string(buf)]; x != 1 {
		t.Errorf(`m[string([]byte("1"))] = %d, want 1`, x)
	}
	buf[0] = '2'
	if x := m[string(buf)]; x != 2 {
		t.Errorf(`m[string([]byte("2"))] = %d, want 2`, x)
	}

	var x int
	n := testing.AllocsPerRun(100, func() {
		x += m[string(buf)]
	})
	if n != 0 {
		t.Errorf("AllocsPerRun for m[string(buf)] = %v, want 0", n)
	}

	x = 0
	n = testing.AllocsPerRun(100, func() {
		y, ok := m[string(buf)]
		if !ok {
			panic("!ok")
		}
		x += y
	})
	if n != 0 {
		t.Errorf("AllocsPerRun for x,ok = m[string(buf)] = %v, want 0", n)
	}
}

func TestMapLargeKeyNoPointer(t *testing.T) {
	const (
		I = 1000
		N = 64
	)
	type T [N]int
	m := make(map[T]int)
	for i := 0; i < I; i++ {
		var v T
		for j := 0; j < N; j++ {
			v[j] = i + j
		}
		m[v] = i
	}
	runtime.GC()
	for i := 0; i < I; i++ {
		var v T
		for j := 0; j < N; j++ {
			v[j] = i + j
		}
		if m[v] != i {
			t.Fatalf("corrupted map: want %+v, got %+v", i, m[v])
		}
	}
}

func TestMapLargeValNoPointer(t *testing.T) {
	const (
		I = 1000
		N = 64
	)
	type T [N]int
	m := make(map[int]T)
	for i := 0; i < I; i++ {
		var v T
		for j := 0; j < N; j++ {
			v[j] = i + j
		}
		m[i] = v
	}
	runtime.GC()
	for i := 0; i < I; i++ {
		var v T
		for j := 0; j < N; j++ {
			v[j] = i + j
		}
		v1 := m[i]
		for j := 0; j < N; j++ {
			if v1[j] != v[j] {
				t.Fatalf("corrupted map: want %+v, got %+v", v, v1)
			}
		}
	}
}

func benchmarkMapPop(b *testing.B, n int) {
	m := map[int]int{}
	for i := 0; i < b.N; i++ {
		for j := 0; j < n; j++ {
			m[j] = j
		}
		for j := 0; j < n; j++ {
			// Use iterator to pop an element.
			// We want this to be fast, see issue 8412.
			for k := range m {
				delete(m, k)
				break
			}
		}
	}
}

func BenchmarkMapPop100(b *testing.B)   { benchmarkMapPop(b, 100) }
func BenchmarkMapPop1000(b *testing.B)  { benchmarkMapPop(b, 1000) }
func BenchmarkMapPop10000(b *testing.B) { benchmarkMapPop(b, 10000) }

func TestNonEscapingMap(t *testing.T) {
	n := testing.AllocsPerRun(1000, func() {
		m := make(map[int]int)
		m[0] = 0
	})
	if n != 0 {
		t.Fatalf("want 0 allocs, got %v", n)
	}
}