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Avoiding bound checks in setunion code #301

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Avoiding bound checks in setunion code #301

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0572790
This should reduce bound checks in a function.
lemire Apr 16, 2021
9f95696
Tuning.
lemire Apr 16, 2021
2e7b454
Removing dead code.
lemire Apr 16, 2021
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33 changes: 18 additions & 15 deletions setutil_generic.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,13 @@

package roaring


func union2by2(set1 []uint16, set2 []uint16, buffer []uint16) int {
pos := 0
k1 := 0
k2 := 0
pos := uint(0)
k1 := uint(0)
k2 := uint(0)
len1 := uint(len(set1))
len2 := uint(len(set2))
if 0 == len(set2) {
buffer = buffer[:len(set1)]
copy(buffer, set1[:])
Expand All @@ -18,31 +21,31 @@ func union2by2(set1 []uint16, set2 []uint16, buffer []uint16) int {
}
s1 := set1[k1]
s2 := set2[k2]
buffer = buffer[:cap(buffer)]
for {
buffer = buffer[:len1 + len2]
for pos < uint(len(buffer)) {
if s1 < s2 {
buffer[pos] = s1
pos++
k1++
if k1 >= len(set1) {
if k1 >= len1 {
copy(buffer[pos:], set2[k2:])
pos += len(set2) - k2
break
pos += len2 - k2
return int(pos)
}
s1 = set1[k1]
} else if s1 == s2 {
buffer[pos] = s1
pos++
k1++
k2++
if k1 >= len(set1) {
if k1 >= len1 {
copy(buffer[pos:], set2[k2:])
pos += len(set2) - k2
pos += len2 - k2
break
}
if k2 >= len(set2) {
if k2 >= len2 {
copy(buffer[pos:], set1[k1:])
pos += len(set1) - k1
pos += len1 - k1
break
}
s1 = set1[k1]
Expand All @@ -51,13 +54,13 @@ func union2by2(set1 []uint16, set2 []uint16, buffer []uint16) int {
buffer[pos] = s2
pos++
k2++
if k2 >= len(set2) {
if k2 >= len2 {
copy(buffer[pos:], set1[k1:])
pos += len(set1) - k1
pos += len1 - k1
break
}
s2 = set2[k2]
}
}
return pos
return int(pos)
}