Merge pull request #79 from prometheus/beorn7/histogram
Use binary search to pick bucket.
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commit
bc1f2b27ad
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@ -17,6 +17,7 @@ import (
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"fmt"
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"hash/fnv"
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"math"
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"sort"
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"sync/atomic"
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"github.com/golang/protobuf/proto"
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@ -231,11 +232,18 @@ func (h *histogram) Desc() *Desc {
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}
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func (h *histogram) Observe(v float64) {
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for i, upperBound := range h.upperBounds {
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if v <= upperBound {
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atomic.AddUint64(&h.counts[i], 1)
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break
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}
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// TODO(beorn7): For small numbers of buckets (<30), a linear search is
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// slightly faster than the binary search. If we really care, we could
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// switch from one search strategy to the other depending on the number
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// of buckets.
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//
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// Microbenchmarks (BenchmarkHistogramNoLabels):
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// 11 buckets: 38.3 ns/op linear - binary 48.7 ns/op
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// 100 buckets: 78.1 ns/op linear - binary 54.9 ns/op
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// 300 buckets: 154 ns/op linear - binary 61.6 ns/op
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i := sort.SearchFloat64s(h.upperBounds, v)
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if i < len(h.counts) {
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atomic.AddUint64(&h.counts[i], 1)
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}
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atomic.AddUint64(&h.count, 1)
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for {
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