forked from mystiq/dex
116 lines
2.7 KiB
Go
116 lines
2.7 KiB
Go
package stats
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import (
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"bytes"
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"fmt"
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"io"
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"math"
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"time"
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)
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// Stats is a simple helper for gathering additional statistics like histogram
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// during benchmarks. This is not thread safe.
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type Stats struct {
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numBuckets int
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unit time.Duration
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min, max int64
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histogram *Histogram
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durations durationSlice
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dirty bool
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}
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type durationSlice []time.Duration
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// NewStats creates a new Stats instance. If numBuckets is not positive,
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// the default value (16) will be used.
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func NewStats(numBuckets int) *Stats {
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if numBuckets <= 0 {
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numBuckets = 16
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}
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return &Stats{
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// Use one more bucket for the last unbounded bucket.
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numBuckets: numBuckets + 1,
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durations: make(durationSlice, 0, 100000),
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}
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}
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// Add adds an elapsed time per operation to the stats.
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func (stats *Stats) Add(d time.Duration) {
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stats.durations = append(stats.durations, d)
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stats.dirty = true
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}
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// Clear resets the stats, removing all values.
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func (stats *Stats) Clear() {
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stats.durations = stats.durations[:0]
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stats.histogram = nil
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stats.dirty = false
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}
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// maybeUpdate updates internal stat data if there was any newly added
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// stats since this was updated.
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func (stats *Stats) maybeUpdate() {
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if !stats.dirty {
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return
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}
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stats.min = math.MaxInt64
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stats.max = 0
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for _, d := range stats.durations {
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if stats.min > int64(d) {
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stats.min = int64(d)
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}
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if stats.max < int64(d) {
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stats.max = int64(d)
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}
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}
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// Use the largest unit that can represent the minimum time duration.
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stats.unit = time.Nanosecond
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for _, u := range []time.Duration{time.Microsecond, time.Millisecond, time.Second} {
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if stats.min <= int64(u) {
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break
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}
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stats.unit = u
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}
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// Adjust the min/max according to the new unit.
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stats.min /= int64(stats.unit)
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stats.max /= int64(stats.unit)
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numBuckets := stats.numBuckets
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if n := int(stats.max - stats.min + 1); n < numBuckets {
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numBuckets = n
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}
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stats.histogram = NewHistogram(HistogramOptions{
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NumBuckets: numBuckets,
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// max-min(lower bound of last bucket) = (1 + growthFactor)^(numBuckets-2) * baseBucketSize.
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GrowthFactor: math.Pow(float64(stats.max-stats.min), 1/float64(numBuckets-2)) - 1,
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BaseBucketSize: 1.0,
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MinValue: stats.min})
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for _, d := range stats.durations {
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stats.histogram.Add(int64(d / stats.unit))
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}
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stats.dirty = false
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}
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// Print writes textual output of the Stats.
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func (stats *Stats) Print(w io.Writer) {
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stats.maybeUpdate()
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if stats.histogram == nil {
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fmt.Fprint(w, "Histogram (empty)\n")
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} else {
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fmt.Fprintf(w, "Histogram (unit: %s)\n", fmt.Sprintf("%v", stats.unit)[1:])
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stats.histogram.Print(w)
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}
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}
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// String returns the textual output of the Stats as string.
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func (stats *Stats) String() string {
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var b bytes.Buffer
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stats.Print(&b)
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return b.String()
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}
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