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Remove bounds checks
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@mhr3
mhr3 committed Oct 29, 2023
1 parent 2cc58bd commit 9625e3e
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Showing 3 changed files with 176 additions and 31 deletions.
110 changes: 79 additions & 31 deletions bitset.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -247,8 +247,13 @@ func (b *BitSet) FlipRange(start, end uint) *BitSet {
var startWord uint = start >> log2WordSize
var endWord uint = end >> log2WordSize
b.set[startWord] ^= ^(^uint64(0) << wordsIndex(start))
for i := startWord; i < endWord; i++ {
b.set[i] = ^b.set[i]
if endWord > 0 {
// bounds check elimination
data := b.set
_ = data[endWord-1]
for i := startWord; i < endWord; i++ {
data[i] = ^data[i]
}
}
if end&(wordSize-1) != 0 {
b.set[endWord] ^= ^uint64(0) >> wordsIndex(-end)
Expand Down Expand Up @@ -427,7 +432,11 @@ func (b *BitSet) NextSet(i uint) (uint, bool) {
if w != 0 {
return i + trailingZeroes64(w), true
}
x = x + 1
x++
// bounds check elimination in the loop
if x < 0 {
return 0, false
}
for x < len(b.set) {
if b.set[x] != 0 {
return uint(x)*wordSize + trailingZeroes64(b.set[x]), true
Expand Down Expand Up @@ -516,6 +525,10 @@ func (b *BitSet) NextClear(i uint) (uint, bool) {
return index, true
}
x++
// bounds check elimination in the loop
if x < 0 {
return 0, false
}
for x < len(b.set) {
index = uint(x)*wordSize + trailingZeroes64(^b.set[x])
if b.set[x] != allBits && index < b.length {
Expand Down Expand Up @@ -615,6 +628,12 @@ func (b *BitSet) Equal(c *BitSet) bool {
return true
}
wn := b.wordCount()
// bounds check elimination
if wn <= 0 {
return true
}
_ = b.set[wn-1]
_ = c.set[wn-1]
for p := 0; p < wn; p++ {
if c.set[p] != b.set[p] {
return false
Expand All @@ -635,9 +654,9 @@ func (b *BitSet) Difference(compare *BitSet) (result *BitSet) {
panicIfNull(b)
panicIfNull(compare)
result = b.Clone() // clone b (in case b is bigger than compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
for i := 0; i < l; i++ {
result.set[i] = b.set[i] &^ compare.set[i]
Expand All @@ -649,9 +668,9 @@ func (b *BitSet) Difference(compare *BitSet) (result *BitSet) {
func (b *BitSet) DifferenceCardinality(compare *BitSet) uint {
panicIfNull(b)
panicIfNull(compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
cnt := uint64(0)
cnt += popcntMaskSlice(b.set[:l], compare.set[:l])
Expand All @@ -664,12 +683,19 @@ func (b *BitSet) DifferenceCardinality(compare *BitSet) uint {
func (b *BitSet) InPlaceDifference(compare *BitSet) {
panicIfNull(b)
panicIfNull(compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
if l <= 0 {
return
}
// bounds check elimination
data, cmpData := b.set, compare.set
_ = data[l-1]
_ = cmpData[l-1]
for i := 0; i < l; i++ {
b.set[i] &^= compare.set[i]
data[i] &^= cmpData[i]
}
}

Expand Down Expand Up @@ -712,15 +738,24 @@ func (b *BitSet) IntersectionCardinality(compare *BitSet) uint {
func (b *BitSet) InPlaceIntersection(compare *BitSet) {
panicIfNull(b)
panicIfNull(compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
}
for i := 0; i < l; i++ {
b.set[i] &= compare.set[i]
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
if l > 0 {
// bounds check elimination
data, cmpData := b.set, compare.set
_ = data[l-1]
_ = cmpData[l-1]

for i := 0; i < l; i++ {
data[i] &= cmpData[i]
}
}
for i := l; i < len(b.set); i++ {
b.set[i] = 0
if l >= 0 {
for i := l; i < len(b.set); i++ {
b.set[i] = 0
}
}
if compare.length > 0 {
if compare.length-1 >= b.length {
Expand Down Expand Up @@ -760,15 +795,22 @@ func (b *BitSet) UnionCardinality(compare *BitSet) uint {
func (b *BitSet) InPlaceUnion(compare *BitSet) {
panicIfNull(b)
panicIfNull(compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
if compare.length > 0 && compare.length-1 >= b.length {
b.extendSet(compare.length - 1)
}
for i := 0; i < l; i++ {
b.set[i] |= compare.set[i]
if l > 0 {
// bounds check elimination
data, cmpData := b.set, compare.set
_ = data[l-1]
_ = cmpData[l-1]

for i := 0; i < l; i++ {
data[i] |= cmpData[i]
}
}
if len(compare.set) > l {
for i := l; i < len(compare.set); i++ {
Expand Down Expand Up @@ -808,15 +850,21 @@ func (b *BitSet) SymmetricDifferenceCardinality(compare *BitSet) uint {
func (b *BitSet) InPlaceSymmetricDifference(compare *BitSet) {
panicIfNull(b)
panicIfNull(compare)
l := int(compare.wordCount())
if l > int(b.wordCount()) {
l = int(b.wordCount())
l := compare.wordCount()
if l > b.wordCount() {
l = b.wordCount()
}
if compare.length > 0 && compare.length-1 >= b.length {
b.extendSet(compare.length - 1)
}
for i := 0; i < l; i++ {
b.set[i] ^= compare.set[i]
if l > 0 {
// bounds check elimination
data, cmpData := b.set, compare.set
_ = data[l-1]
_ = cmpData[l-1]
for i := 0; i < l; i++ {
data[i] ^= cmpData[i]
}
}
if len(compare.set) > l {
for i := l; i < len(compare.set); i++ {
Expand Down
81 changes: 81 additions & 0 deletions bitset_benchmark_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,87 @@ func BenchmarkSparseIterate(b *testing.B) {
}
}

// go test -bench=BitsetOps
func BenchmarkBitsetOps(b *testing.B) {
// let's not write into s inside the benchmarks
s := New(100000)
for i := 0; i < 100000; i += 100 {
s.Set(uint(i))
}
cpy := s.Clone()

b.Run("Equal", func(b *testing.B) {
for i := 0; i < b.N; i++ {
s.Equal(cpy)
}
})

b.Run("FlipRange", func(b *testing.B) {
s = s.Clone()
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.FlipRange(0, 100000)
}
})

b.Run("NextSet", func(b *testing.B) {
s = New(100000)
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.NextSet(0)
}
})

b.Run("NextClear", func(b *testing.B) {
s = New(100000)
s.FlipRange(0, 100000)
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.NextClear(0)
}
})

b.Run("DifferenceCardinality", func(b *testing.B) {
empty := New(100000)
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.DifferenceCardinality(empty)
}
})

b.Run("InPlaceDifference", func(b *testing.B) {
s = s.Clone()
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.InPlaceDifference(cpy)
}
})

b.Run("InPlaceUnion", func(b *testing.B) {
s = s.Clone()
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.InPlaceUnion(cpy)
}
})

b.Run("InPlaceIntersection", func(b *testing.B) {
s = s.Clone()
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.InPlaceIntersection(cpy)
}
})

b.Run("InPlaceSymmetricDifference", func(b *testing.B) {
s = s.Clone()
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.InPlaceSymmetricDifference(cpy)
}
})
}

// go test -bench=LemireCreate
// see http://lemire.me/blog/2016/09/22/swift-versus-java-the-bitset-performance-test/
func BenchmarkLemireCreate(b *testing.B) {
Expand Down
16 changes: 16 additions & 0 deletions popcnt_19.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,10 @@ func popcntSlice(s []uint64) uint64 {

func popcntMaskSlice(s, m []uint64) uint64 {
var cnt int
// this explicit check eliminates a bounds check in the loop
if len(m) < len(s) {
panic("mask slice is too short")
}
for i := range s {
cnt += bits.OnesCount64(s[i] &^ m[i])
}
Expand All @@ -23,6 +27,10 @@ func popcntMaskSlice(s, m []uint64) uint64 {

func popcntAndSlice(s, m []uint64) uint64 {
var cnt int
// this explicit check eliminates a bounds check in the loop
if len(m) < len(s) {
panic("mask slice is too short")
}
for i := range s {
cnt += bits.OnesCount64(s[i] & m[i])
}
Expand All @@ -31,6 +39,10 @@ func popcntAndSlice(s, m []uint64) uint64 {

func popcntOrSlice(s, m []uint64) uint64 {
var cnt int
// this explicit check eliminates a bounds check in the loop
if len(m) < len(s) {
panic("mask slice is too short")
}
for i := range s {
cnt += bits.OnesCount64(s[i] | m[i])
}
Expand All @@ -39,6 +51,10 @@ func popcntOrSlice(s, m []uint64) uint64 {

func popcntXorSlice(s, m []uint64) uint64 {
var cnt int
// this explicit check eliminates a bounds check in the loop
if len(m) < len(s) {
panic("mask slice is too short")
}
for i := range s {
cnt += bits.OnesCount64(s[i] ^ m[i])
}
Expand Down

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