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Simplify unionArrayArray

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Also short-circuit it in some cases.
This commit is contained in:
Seebs 2019-12-17 14:58:32 -06:00
parent 1af016df84
commit 83aa505673
1 changed files with 65 additions and 54 deletions
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119
roaring/roaring.go
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@ -3688,41 +3688,43 @@ func union(a, b *Container) *Container {
func unionArrayArray(a, b *Container) *Container {
statsHit("union/ArrayArray")
aa, ab := a.array(), b.array()
na, nb := len(aa), len(ab)
output := make([]uint16, na+nb)
n := 0
for i, j := 0, 0; ; {
if i >= na && j >= nb {
break
} else if i < na && j >= nb {
output[n] = aa[i]
n++
i++
continue
} else if i >= na && j < nb {
output[n] = ab[j]
n++
j++
continue
}
va, vb := aa[i], ab[j]
if a.N() == 0 {
return b
}
if b.N() == 0 {
return a
}
s1, s2 := a.array(), b.array()
n1, n2 := len(s1), len(s2)
output := make([]uint16, 0, n1+n2)
i, j := 0, 0
for {
va, vb := s1[i], s2[j]
if va < vb {
output[n] = va
n++
output = append(output, va)
i++
} else if va > vb {
output[n] = vb
n++
output = append(output, vb)
j++
} else {
output[n] = va
n++
i, j = i+1, j+1
output = append(output, va)
i++
j++
}
// It's possible we hit the ends at the same time,
// in which case the append will copy 0 items. This
// is cheaper than performing a separate conditional
// check every time...
if j >= n2 {
output = append(output, s1[i:]...)
break
}
if i >= n1 {
output = append(output, s2[j:]...)
break
}
}
return NewContainerArray(output[:n])
return NewContainerArray(output)
}
// unionArrayArrayInPlace does what it sounds like -- tries to combine
@ -3730,47 +3732,56 @@ func unionArrayArray(a, b *Container) *Container {
// of a good array size, so it could be up to twice that size, temporarily.
func unionArrayArrayInPlace(a, b *Container) *Container {
statsHit("union/ArrayArrayInPlace")
aa, ab := a.array(), b.array()
na, nb := len(aa), len(ab)
output := make([]uint16, na+nb)
outN := 0
for i, j := 0, 0; ; {
if i >= na && j >= nb {
break
} else if i < na && j >= nb {
copy(output[outN:], aa[i:])
outN += na - i
break
} else if i >= na && j < nb {
copy(output[outN:], ab[j:])
outN += nb - j
break
if a.N() == 0 {
if b.N() != 0 {
// for InPlace, we actually want to ensure that
// we update a, as long as it's not frozen.
a = a.Thaw()
a.setArray(b.array())
return a.optimize()
}
va, vb := aa[i], ab[j]
return a
}
if b.N() == 0 {
return a
}
s1, s2 := a.array(), b.array()
n1, n2 := len(s1), len(s2)
output := make([]uint16, 0, n1+n2)
i, j := 0, 0
for {
va, vb := s1[i], s2[j]
if va < vb {
output[outN] = va
outN++
output = append(output, va)
i++
} else if va > vb {
output[outN] = vb
outN++
output = append(output, vb)
j++
} else {
output[outN] = va
outN++
output = append(output, va)
i++
j++
}
// It's possible we hit the ends at the same time,
// in which case the append will copy 0 items. This
// is cheaper than performing a separate conditional
// check every time...
if j >= n2 {
output = append(output, s1[i:]...)
break
}
if i >= n1 {
output = append(output, s2[j:]...)
break
}
}
// a union can't omit anything that was previously in a, so if
// the output is the same length, nothing changed.
if len(output) != int(a.N()) {
a = a.Thaw()
a.setArray(output[:outN])
a = a.optimize()
a.setArray(output)
}
return a
return a.optimize()
}
// unionArrayRun optimistically assumes that the result will be a run container,