src/runtime/map_test.go - go - Git at Google

 // 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 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) }
	// 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 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) }