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further optimise LatestMap.Merge

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This commit is contained in:
Matthias Radestock
2016-08-14 17:05:37 +01:00
parent 73f1299e20
commit 039ee322b0
1 changed files with 12 additions and 3 deletions
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15
report/latest_map.go
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@@ -52,8 +52,13 @@ func (m LatestMap) Size() int {
return m.Map.Size()
}
// Merge produces a fresh LatestMap, container the kers from both inputs. When
// both inputs container the same key, the latter value is used.
// Merge produces a fresh LatestMap, containing the keys from both
// inputs. When both inputs contain the same key, the more recent
// value is used.
//
// NB: This function operates more efficiently - performing less
// memory allocation and copying - when the entries in the target are
// younger than the entries in the argument.
func (m LatestMap) Merge(other LatestMap) LatestMap {
var (
mSize = m.Size()
@@ -66,7 +71,11 @@ func (m LatestMap) Merge(other LatestMap) LatestMap {
return other
case otherSize == 0:
return m
case mSize < otherSize:
case mSize*2 < otherSize:
// NB: We forgo the "merge older into younger" optimisation
// here in favour of "merge smaller into larger". The
// assumption behind the "*2" is that typically all the keys
// in the smaller map are in the larger map.
output, iter = iter, output
}