github.com/dgraph-io/sroar@v0.0.0-20220527172339-b92b7eaaf6e0/bitmap_test.go

package sroar

import (
	"math"
	"math/rand"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

func fill(c []uint16, b uint16) {
	for i := range c[startIdx:] {
		c[i+int(startIdx)] = b
	}
}

func TestModify(t *testing.T) {
	data := make([]uint16, 16)
	s := toUint64Slice(data)
	for i := 0; i < len(s); i++ {
		s[i] = uint64(i)
	}

	o := toUint64Slice(data)
	for i := 0; i < len(o); i++ {
		require.Equal(t, uint64(i), o[i])
	}
}

func TestContainer(t *testing.T) {
	ra := NewBitmap()

	// We're creating a container of size 64 words. 4 of these would be used for
	// the header. So, the data can only live in 60 words.
	offset := ra.newContainer(64)
	c := ra.getContainer(offset)
	require.Equal(t, uint16(64), ra.data[offset])
	require.Equal(t, uint16(0), c[indexCardinality])

	fill(c, 0xFF)
	for i, u := range c[startIdx:] {
		if i < 60 {
			require.Equalf(t, uint16(0xFF), u, "at index: %d", i)
		} else {
			require.Equalf(t, uint16(0x00), u, "at index: %d", i)
		}
	}

	offset2 := ra.newContainer(32) // Add a second container.
	c2 := ra.getContainer(offset2)
	require.Equal(t, uint16(32), ra.data[offset2])
	fill(c2, 0xEE)

	// Expand the first container. This would push out the second container, so update its offset.
	ra.expandContainer(offset)
	offset2 += 64

	// Check if the second container is correct.
	c2 = ra.getContainer(offset2)
	require.Equal(t, uint16(32), ra.data[offset2])
	require.Equal(t, 32, len(c2))
	for _, val := range c2[startIdx:] {
		require.Equal(t, uint16(0xEE), val)
	}

	// Check if the first container is correct.
	c = ra.getContainer(offset)
	require.Equal(t, uint16(128), ra.data[offset])
	require.Equal(t, 128, len(c))
	for i, u := range c[startIdx:] {
		if i < 60 {
			require.Equalf(t, uint16(0xFF), u, "at index: %d", i)
		} else {
			require.Equalf(t, uint16(0x00), u, "at index: %d", i)
		}
	}
}

func TestKey(t *testing.T) {
	ra := NewBitmap()
	for i := 1; i <= 10; i++ {
		ra.Set(uint64(i))
	}

	off, has := ra.keys.getValue(0)
	require.True(t, has)
	c := ra.getContainer(off)
	require.Equal(t, uint16(10), c[indexCardinality])

	// Create 10 containers
	for i := 0; i < 10; i++ {
		t.Logf("Creating a new container: %d\n", i)
		ra.Set(uint64(i)<<16 + 1)
	}

	for i := 0; i < 10; i++ {
		ra.Set(uint64(i)<<16 + 2)
	}

	for i := 1; i < 10; i++ {
		offset, has := ra.keys.getValue(uint64(i) << 16)
		require.True(t, has)
		c = ra.getContainer(offset)
		require.Equal(t, uint16(2), c[indexCardinality])
	}

	// Do add in the reverse order.
	for i := 19; i >= 10; i-- {
		ra.Set(uint64(i)<<16 + 2)
	}

	for i := 10; i < 20; i++ {
		offset, has := ra.keys.getValue(uint64(i) << 16)
		require.True(t, has)
		c = ra.getContainer(offset)
		require.Equal(t, uint16(1), c[indexCardinality])
	}
}

func TestEdgeCase(t *testing.T) {
	ra := NewBitmap()

	require.True(t, ra.Set(65536))
	require.True(t, ra.Contains(65536))
}

func TestBulkAdd(t *testing.T) {
	ra := NewBitmap()
	m := make(map[uint64]struct{})
	max := int64(64 << 16)
	start := time.Now()

	var cnt int
	for i := 0; ; i++ {
		if i%100 == 0 && time.Since(start) > time.Second {
			cnt++
			start = time.Now()
			// t.Logf("Bitmap:\n%s\n", ra)
			if cnt == 3 {
				t.Logf("Breaking out of the loop\n")
				break
			}
		}
		x := uint64(rand.Int63n(max))

		if _, has := m[x]; has {
			if !ra.Contains(x) {
				t.Logf("x should be present: %d %#x. Bitmap: %s\n", x, x, ra)
				off, found := ra.keys.getValue(x & mask)
				assert(found)
				c := ra.getContainer(off)
				lo := uint16(x)
				t.Logf("x: %#x lo: %#x. offset: %d\n", x, lo, off)
				switch c[indexType] {
				case typeArray:
				case typeBitmap:
					idx := lo / 16
					pos := lo % 16
					t.Logf("At idx: %d. Pos: %d val: %#b\n", idx, pos, c[startIdx+idx])
				}

				t.Logf("Added: %d %#x. Added: %v\n", x, x, ra.Set(x))
				t.Logf("After add. has: %v\n", ra.Contains(x))

				// 				t.Logf("Hex dump of container at offset: %d\n%s\n", off, hex.Dump(toByteSlice(c)))
				t.FailNow()
			}
			continue
		}
		m[x] = struct{}{}
		// fmt.Printf("Setting x: %#x\n", x)
		if added := ra.Set(x); !added {
			t.Logf("Unable to set: %d %#x\n", x, x)
			t.Logf("ra.Has(x): %v\n", ra.Contains(x))
			t.FailNow()
		}
		// for x := range m {
		// 	if !ra.Has(x) {
		// 		t.Logf("has(x) failed: %#x\n", x)
		// 		t.Logf("Debug: %s\n", ra.Debug(x))
		// 		t.FailNow()
		// 	}
		// }
		// require.Truef(t, ra.Set(x), "Unable to set x: %d %#x\n", x, x)
	}
	t.Logf("Card: %d\n", len(m))
	require.Equalf(t, len(m), ra.GetCardinality(), "Bitmap:\n%s\n", ra)
	for x := range m {
		require.True(t, ra.Contains(x))
	}

	// _, has := ra.keys.getValue(0)
	// require.True(t, has)
	// for i := uint64(1); i <= max; i++ {
	// 	require.Truef(t, ra.Has(i), "i=%d", i)
	// }
	// t.Logf("Data size: %d\n", len(ra.data))

	t.Logf("Copying data. Size: %d\n", len(ra.data))
	dup := make([]uint16, len(ra.data))
	copy(dup, ra.data)

	ra2 := FromBuffer(toByteSlice(dup))
	require.Equal(t, len(m), ra2.GetCardinality())
	for x := range m {
		require.True(t, ra2.Contains(x))
	}
}

func TestBitmapUint64Max(t *testing.T) {
	bm := NewBitmap()

	edges := []uint64{0, math.MaxUint8, math.MaxUint16, math.MaxUint32, math.MaxUint64}
	for _, e := range edges {
		bm.Set(e)
	}
	for _, e := range edges {
		require.True(t, bm.Contains(e))
	}
}

func TestBitmapZero(t *testing.T) {
	bm1 := NewBitmap()
	bm1.Set(1)
	uids := bm1.ToArray()
	require.Equal(t, 1, len(uids))
	for _, u := range uids {
		require.Equal(t, uint64(1), u)
	}

	bm2 := NewBitmap()
	bm2.Set(2)

	bm3 := Or(bm1, bm2)
	require.False(t, bm3.Contains(0))
	require.True(t, bm3.Contains(1))
	require.True(t, bm3.Contains(2))
	require.Equal(t, 2, bm3.GetCardinality())
}

func TestBitmapOps(t *testing.T) {
	M := int64(10000)
	// smaller bitmap would always operate with [0, M) range.
	// max for each bitmap = M * F
	F := []int64{1, 10, 100, 1000}
	N := 10000

	for _, f := range F {
		t.Logf("Using N: %d M: %d F: %d\n", N, M, f)
		small, big := NewBitmap(), NewBitmap()
		occ := make(map[uint64]int)
		smallMap := make(map[uint64]struct{})
		bigMap := make(map[uint64]struct{})

		for i := 0; i < N; i++ {
			smallx := uint64(rand.Int63n(M))

			_, has := smallMap[smallx]
			added := small.Set(smallx)
			if has {
				require.False(t, added, "Can't readd already present x: %d", smallx)
			}
			smallMap[smallx] = struct{}{}

			bigx := uint64(rand.Int63n(M * f))
			_, has = bigMap[bigx]
			added = big.Set(bigx)
			if has {
				require.False(t, added, "Can't readd already present x: %d", bigx)
			}
			bigMap[bigx] = struct{}{}

			occ[smallx] |= 0x01 // binary 0001
			occ[bigx] |= 0x02   // binary 0010
		}
		require.Equal(t, len(smallMap), small.GetCardinality())
		require.Equal(t, len(bigMap), big.GetCardinality())

		bitOr := Or(small, big)
		bitAnd := And(small, big)

		t.Logf("Sizes. small: %d big: %d, bitOr: %d bitAnd: %d\n",
			small.GetCardinality(), big.GetCardinality(),
			bitOr.GetCardinality(), bitAnd.GetCardinality())

		cntOr, cntAnd := 0, 0
		for x, freq := range occ {
			if freq == 0x00 {
				require.Failf(t, "Failed", "Value of freq can't be zero. Found: %#x\n", freq)
			} else if freq == 0x01 {
				_, has := smallMap[x]
				require.True(t, has)
				require.True(t, small.Contains(x))
				require.Truef(t, bitOr.Contains(x), "Expected %d %#x. But, not found. freq: %#x\n",
					x, x, freq)
				cntOr++

			} else if freq == 0x02 {
				// one of them has it.
				_, has := bigMap[x]
				require.True(t, has)
				require.True(t, big.Contains(x))
				require.Truef(t, bitOr.Contains(x), "Expected %d %#x. But, not found. freq: %#x\n",
					x, x, freq)
				cntOr++

			} else if freq == 0x03 {
				require.True(t, small.Contains(x))
				require.True(t, big.Contains(x))
				require.Truef(t, bitAnd.Contains(x), "x: %#x\n", x)
				cntOr++
				cntAnd++
			} else {
				require.Failf(t, "Failed", "Value of freq can't exceed 0x03. Found: %#x\n", freq)
			}
		}
		if cntAnd != bitAnd.GetCardinality() {
			uids := bitAnd.ToArray()
			t.Logf("Len Uids: %d Card: %d cntAnd: %d. Occ: %d\n", len(uids), bitAnd.GetCardinality(), cntAnd, len(occ))

			uidMap := make(map[uint64]struct{})
			for _, u := range uids {
				uidMap[u] = struct{}{}
			}
			for u := range occ {
				delete(uidMap, u)
			}
			for x := range uidMap {
				t.Logf("Remaining uids in UidMap: %d %#b\n", x, x)
			}
			require.FailNow(t, "Cardinality isn't matching")
		}
		require.Equal(t, cntOr, bitOr.GetCardinality())
		require.Equal(t, cntAnd, bitAnd.GetCardinality())
	}
}

func TestUint16(t *testing.T) {
	a := uint16(0xfeff)
	b := uint16(0x100)
	t.Logf("a & b: %#x", a&b)
	var x uint16
	for i := 0; i < 100000; i++ {
		prev := x
		x++
		if x <= prev {
			// This triggers when prev = 0xFFFF.
			// require.Failf(t, "x<=prev", "x %d <= prev %d", x, prev)
		}
	}
}

func TestSetGet(t *testing.T) {
	bm := NewBitmap()
	N := int(1e6)
	for i := 0; i < N; i++ {
		bm.Set(uint64(i))
	}
	for i := 0; i < N; i++ {
		has := bm.Contains(uint64(i))
		require.True(t, has)
	}
}

func TestSetSorted(t *testing.T) {
	check := func(n int) {
		var arr []uint64
		for i := 0; i < n; i++ {
			arr = append(arr, uint64(i))
		}
		r := FromSortedList(arr)
		require.Equal(t, len(arr), r.GetCardinality())

		rarr := r.ToArray()
		for i := 0; i < n; i++ {
			require.Equal(t, uint64(i), rarr[i])
		}

		r.Set(uint64(n))
		require.True(t, r.Contains(uint64(n)))
	}
	check(10)
	check(1e6)
}

func TestAnd(t *testing.T) {
	a := NewBitmap()
	b := NewBitmap()

	N := int(1e7)
	for i := 0; i < N; i++ {
		if i%2 == 0 {
			a.Set(uint64(i))
		} else {
			b.Set(uint64(i))
		}
	}
	require.Equal(t, N/2, a.GetCardinality())
	require.Equal(t, N/2, b.GetCardinality())
	res := And(a, b)
	require.Equal(t, 0, res.GetCardinality())
	a.And(b)
	require.Equal(t, 0, a.GetCardinality())
}

func TestAnd2(t *testing.T) {
	a := NewBitmap()
	n := int(1e7)

	for i := 0; i < n; i++ {
		a.Set(uint64(i))
	}
	require.Equal(t, n, a.GetCardinality())
	a.RemoveRange(0, uint64(n/2))

	for i := 0; i < n; i++ {
		a.Set(uint64(i))
	}
	require.Equal(t, n, a.GetCardinality())
}

func TestAndNot(t *testing.T) {
	a := NewBitmap()
	b := NewBitmap()

	N := int(1e7)
	for i := 0; i < N; i++ {
		a.Set(uint64(i))
		if i < N/2 {
			b.Set(uint64(i))
		}
	}
	require.Equal(t, N, a.GetCardinality())
	require.Equal(t, N/2, b.GetCardinality())

	a.AndNot(b)
	require.Equal(t, N/2, a.GetCardinality())

	// Test for case when array container will be generated.
	a = NewBitmap()
	b = NewBitmap()

	a.SetMany([]uint64{1, 2, 3, 4})
	b.SetMany([]uint64{3, 4, 5, 6})

	a.AndNot(b)
	require.Equal(t, []uint64{1, 2}, a.ToArray())

	// Test for case when bitmap container will be generated.
	a = NewBitmap()
	b = NewBitmap()
	for i := 0; i < 10000; i++ {
		a.Set(uint64(i))
		if i < 7000 {
			b.Set(uint64(i))
		}
	}
	a.AndNot(b)
	require.Equal(t, 3000, a.GetCardinality())
	for i := 0; i < 10000; i++ {
		if i < 7000 {
			require.False(t, a.Contains(uint64(i)))
		} else {
			require.True(t, a.Contains(uint64(i)))
		}
	}
}

func TestAndNot2(t *testing.T) {
	a := NewBitmap()
	b := NewBitmap()
	n := int(1e6)

	for i := 0; i < n/2; i++ {
		a.Set(uint64(i))
	}
	for i := n / 2; i < n; i++ {
		b.Set(uint64(i))
	}
	require.Equal(t, n/2, a.GetCardinality())
	a.AndNot(b)
	require.Equal(t, n/2, a.GetCardinality())

}

func TestOr(t *testing.T) {
	a := NewBitmap()
	b := NewBitmap()

	N := int(1e7)
	for i := 0; i < N; i++ {
		if i%2 == 0 {
			a.Set(uint64(i))
		} else {
			b.Set(uint64(i))
		}
	}
	require.Equal(t, N/2, a.GetCardinality())
	require.Equal(t, N/2, b.GetCardinality())
	res := Or(a, b)
	require.Equal(t, N, res.GetCardinality())
	a.or(b, 0)
	require.Equal(t, N, a.GetCardinality())
}

func TestCardinality(t *testing.T) {
	a := NewBitmap()
	n := 1 << 20
	for i := 0; i < n; i++ {
		a.Set(uint64(i))
	}
	require.Equal(t, n, a.GetCardinality())
}

func TestRemove(t *testing.T) {
	a := NewBitmap()
	N := int(1e7)
	for i := 0; i < N; i++ {
		a.Set(uint64(i))
	}
	require.Equal(t, N, a.GetCardinality())
	for i := 0; i < N/2; i++ {
		require.True(t, a.Remove(uint64(i)))
	}
	require.Equal(t, N/2, a.GetCardinality())

	// Remove elelemts which doesn't exist should be no-op
	for i := 0; i < N/2; i++ {
		require.False(t, a.Remove(uint64(i)))
	}
	require.Equal(t, N/2, a.GetCardinality())

	for i := 0; i < N/2; i++ {
		require.True(t, a.Remove(uint64(i+N/2)))
	}
	require.Equal(t, 0, a.GetCardinality())
}

func TestContainerRemoveRange(t *testing.T) {
	ra := NewBitmap()

	type cases struct {
		lo       uint16
		hi       uint16
		expected []uint16
	}

	testBitmap := func(tc cases) {
		offset := ra.newContainer(maxContainerSize)
		c := ra.getContainer(offset)
		c[indexType] = typeBitmap
		a := bitmap(c)

		for i := 1; i <= 5; i++ {
			a.add(uint16(5 * i))
		}
		a.removeRange(tc.lo, tc.hi)
		result := a.all()
		require.Equalf(t, len(tc.expected), getCardinality(a), "case: %+v, actual:%v\n", tc, result)
		require.Equalf(t, tc.expected, result, "case: %+v actual: %v\n", tc, result)
	}

	testArray := func(tc cases) {
		offset := ra.newContainer(maxContainerSize)
		c := ra.getContainer(offset)
		c[indexType] = typeArray
		a := array(c)

		for i := 1; i <= 5; i++ {
			a.add(uint16(5 * i))
		}
		a.removeRange(tc.lo, tc.hi)
		result := a.all()
		require.Equalf(t, len(tc.expected), getCardinality(a), "case: %+v, actual:%v\n", tc, result)
		require.Equalf(t, tc.expected, result, "case: %+v actual: %v\n", tc, result)
	}

	tests := []cases{
		{8, 22, []uint16{5, 25}},
		{8, 20, []uint16{5, 25}},
		{10, 22, []uint16{5, 25}},
		{10, 20, []uint16{5, 25}},
		{7, 11, []uint16{5, 15, 20, 25}},
		{7, 10, []uint16{5, 15, 20, 25}},
		{10, 11, []uint16{5, 15, 20, 25}},
		{0, 0, []uint16{5, 10, 15, 20, 25}},
		{30, 30, []uint16{5, 10, 15, 20, 25}},
	}

	for _, tc := range tests {
		testBitmap(tc)
		testArray(tc)
	}
}

func TestRemoveRange(t *testing.T) {
	a := NewBitmap()
	N := int(1e7)
	for i := 0; i < N; i++ {
		a.Set(uint64(i))
	}
	a.RemoveRange(0, 0)
	require.Equal(t, N, a.GetCardinality())

	require.Equal(t, N, a.GetCardinality())
	a.RemoveRange(uint64(N/4), uint64(N/2))
	require.Equal(t, 3*N/4, a.GetCardinality())

	a.RemoveRange(0, uint64(N/2))
	require.Equal(t, N/2, a.GetCardinality())

	a.RemoveRange(uint64(N/2), uint64(N))
	require.Equal(t, 0, a.GetCardinality())
	a.Set(uint64(N / 4))
	a.Set(uint64(N / 2))
	a.Set(uint64(3 * N / 4))
	require.Equal(t, 3, a.GetCardinality())

	var arr []uint64
	for i := 0; i < 123; i++ {
		arr = append(arr, uint64(i))
	}
	b := FromSortedList(arr)
	b.RemoveRange(50, math.MaxUint64)
	require.Equal(t, 50, b.GetCardinality())
}

func TestRemoveRange2(t *testing.T) {
	// High from the last container should not be removed.
	a := NewBitmap()
	for i := 1; i < 10; i++ {
		a.Set(uint64(i * (1 << 16)))
		a.Set(uint64(i*(1<<16)) - 1)
	}
	a.RemoveRange(1<<16, (4<<16)-1)
	require.True(t, a.Contains((4<<16)-1))
}

func TestSelect(t *testing.T) {
	a := NewBitmap()
	N := int(1e4)
	for i := 0; i < N; i++ {
		a.Set(uint64(i))
	}
	for i := 0; i < N; i++ {
		val, err := a.Select(uint64(i))
		require.NoError(t, err)
		require.Equal(t, uint64(i), val)
	}
}

func TestClone(t *testing.T) {
	a := NewBitmap()
	N := int(1e5)

	for i := 0; i < N; i++ {
		a.Set(uint64(rand.Int63n(math.MaxInt64)))
	}
	b := a.Clone()
	require.Equal(t, a.GetCardinality(), b.GetCardinality())
	require.Equal(t, a.ToArray(), b.ToArray())
}

func TestContainerFull(t *testing.T) {
	c := make([]uint16, maxContainerSize)
	b := bitmap(c)
	b[indexType] = typeBitmap
	b[indexSize] = maxContainerSize
	for i := 0; i < 1<<16; i++ {
		b.add(uint16(i))
	}
	require.Equal(t, math.MaxUint16+1, getCardinality(b))

	c2 := make([]uint16, maxContainerSize)
	copy(c2, c)
	b2 := bitmap(c2)

	b.orBitmap(b2, nil, runInline)
	require.Equal(t, math.MaxUint16+1, getCardinality(b))

	setCardinality(b, invalidCardinality)
	b.orBitmap(b2, nil, runInline)
	require.Equal(t, invalidCardinality, getCardinality(b))

	setCardinality(b, b.cardinality())
	require.Equal(t, maxCardinality, getCardinality(b))
}

func TestExtremes(t *testing.T) {
	a := NewBitmap()
	require.Equal(t, uint64(0), a.Minimum())
	require.Equal(t, uint64(0), a.Maximum())

	a.Set(1)
	require.Equal(t, uint64(1), a.Minimum())
	require.Equal(t, uint64(1), a.Maximum())

	a.Set(100000)
	require.Equal(t, uint64(1), a.Minimum())
	require.Equal(t, uint64(100000), a.Maximum())

	a.Remove(100000)
	require.Equal(t, uint64(1), a.Minimum())
	require.Equal(t, uint64(1), a.Maximum())

	a.Remove(1)
	require.Equal(t, uint64(0), a.Minimum())
	require.Equal(t, uint64(0), a.Maximum())

	a.Set(100000)
	require.Equal(t, uint64(100000), a.Minimum())
	require.Equal(t, uint64(100000), a.Maximum())
}

func TestCleanup(t *testing.T) {
	a := NewBitmap()
	n := 10

	for i := 0; i < n; i++ {
		a.Set(uint64((i * (1 << 16))))
	}
	abuf := a.ToBufferWithCopy()

	require.Equal(t, 10, a.keys.numKeys())
	a.RemoveRange(1<<16, 2*(1<<16))
	require.Equal(t, 9, a.keys.numKeys())

	a.RemoveRange(6*(1<<16), 8*(1<<16))
	require.Equal(t, 7, a.keys.numKeys())

	a = FromBufferWithCopy(abuf)
	require.Equal(t, 10, a.keys.numKeys())
	a.Remove(6 * (1 << 16))
	a.RemoveRange(7*(1<<16), 9*(1<<16))
	require.Equal(t, 7, a.keys.numKeys())

	n = int(1e6)
	b := NewBitmap()
	for i := 0; i < n; i++ {
		b.Set(uint64(i))
	}
	b.RemoveRange(0, uint64(n/2))
	require.Equal(t, n/2, b.GetCardinality())
	buf := b.ToBuffer()
	b = FromBuffer(buf)
	require.Equal(t, n/2, b.GetCardinality())
}

func TestCleanup2(t *testing.T) {
	a := NewBitmap()
	n := 10
	for i := 0; i < n; i++ {
		a.Set(uint64(i * (1 << 16)))
	}
	require.Equal(t, n, a.GetCardinality())
	require.Equal(t, n, a.keys.numKeys())

	for i := 0; i < n; i++ {
		if i%2 == 1 {
			a.Remove(uint64(i * (1 << 16)))
		}
	}
	require.Equal(t, n/2, a.GetCardinality())
	require.Equal(t, n, a.keys.numKeys())

	a.Cleanup()
	require.Equal(t, n/2, a.GetCardinality())
	require.Equal(t, n/2, a.keys.numKeys())
}

func TestCleanupSplit(t *testing.T) {
	a := NewBitmap()
	n := int(1e8)

	for i := 0; i < n; i++ {
		a.Set(uint64(i))
	}

	split := func() {
		n := a.GetCardinality()
		mid, err := a.Select(uint64(n / 2))
		require.NoError(t, err)

		b := a.Clone()
		a.RemoveRange(0, mid)
		b.RemoveRange(mid, math.MaxUint64)

		require.Equal(t, n, a.GetCardinality()+b.GetCardinality())
	}
	for a.GetCardinality() > 1 {
		split()
	}
}

func TestIsEmpty(t *testing.T) {
	a := NewBitmap()
	require.True(t, a.IsEmpty())

	n := int(1e6)
	for i := 0; i < n; i++ {
		a.Set(uint64(i))
	}
	require.False(t, a.IsEmpty())
	a.RemoveRange(0, math.MaxUint64)
	require.True(t, a.IsEmpty())
}

func TestRank(t *testing.T) {
	a := NewBitmap()
	n := int(1e6)
	for i := uint64(0); i < uint64(n); i++ {
		a.Set(i)
	}
	for i := 0; i < n; i++ {
		require.Equal(t, i, a.Rank(uint64(i)))
	}
	require.Equal(t, -1, a.Rank(uint64(n)))

	// Check ranks after removing an element.
	a.Remove(100)
	for i := 0; i < n; i++ {
		if i < 100 {
			require.Equal(t, i, a.Rank(uint64(i)))
		} else if i == 100 {
			require.Equal(t, -1, a.Rank(uint64(i)))
		} else {
			require.Equal(t, i-1, a.Rank(uint64(i)))
		}
	}

	// Check ranks after removing a range of elements.
	a.RemoveRange(0, uint64(1e4))
	for i := 0; i < n; i++ {
		if i < 1e4 {
			require.Equal(t, -1, a.Rank(uint64(n)))
		} else {
			require.Equal(t, i-1e4, a.Rank(uint64(i)))
		}
	}
}

func TestSplit(t *testing.T) {
	run := func(n int) {
		r := NewBitmap()
		for i := 1; i <= n; i++ {
			r.Set(uint64(i))
		}
		f := func(start, end uint64) uint64 { return 0 }

		// Split the bitmaps.
		bms := r.Split(f, 1<<10)
		var csum int
		for _, bm := range bms {
			csum += bm.GetCardinality()
		}
		require.Equal(t, n, csum)

		id := uint64(1)
		for _, bm := range bms {
			itr := bm.NewIterator()
			for cur := itr.Next(); cur != 0; cur = itr.Next() {
				require.Equal(t, id, cur)
				id++
			}
		}
	}

	run(2)
	run(11)
	run(1e3)
	run(1e6)
}