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206 lines
5.5 KiB
206 lines
5.5 KiB
/*
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* Copyright 2020 Dgraph Labs, Inc. and Contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package z
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import (
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"fmt"
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"math"
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"strings"
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"github.com/dustin/go-humanize"
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)
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// Creates bounds for an histogram. The bounds are powers of two of the form
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// [2^min_exponent, ..., 2^max_exponent].
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func HistogramBounds(minExponent, maxExponent uint32) []float64 {
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var bounds []float64
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for i := minExponent; i <= maxExponent; i++ {
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bounds = append(bounds, float64(int(1)<<i))
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}
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return bounds
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}
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func Fibonacci(num int) []float64 {
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assert(num > 4)
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bounds := make([]float64, num)
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bounds[0] = 1
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bounds[1] = 2
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for i := 2; i < num; i++ {
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bounds[i] = bounds[i-1] + bounds[i-2]
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}
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return bounds
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}
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// HistogramData stores the information needed to represent the sizes of the keys and values
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// as a histogram.
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type HistogramData struct {
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Bounds []float64
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Count int64
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CountPerBucket []int64
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Min int64
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Max int64
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Sum int64
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}
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// NewHistogramData returns a new instance of HistogramData with properly initialized fields.
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func NewHistogramData(bounds []float64) *HistogramData {
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return &HistogramData{
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Bounds: bounds,
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CountPerBucket: make([]int64, len(bounds)+1),
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Max: 0,
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Min: math.MaxInt64,
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}
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}
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func (histogram *HistogramData) Copy() *HistogramData {
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if histogram == nil {
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return nil
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}
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return &HistogramData{
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Bounds: append([]float64{}, histogram.Bounds...),
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CountPerBucket: append([]int64{}, histogram.CountPerBucket...),
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Count: histogram.Count,
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Min: histogram.Min,
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Max: histogram.Max,
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Sum: histogram.Sum,
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}
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}
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// Update changes the Min and Max fields if value is less than or greater than the current values.
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func (histogram *HistogramData) Update(value int64) {
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if histogram == nil {
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return
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}
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if value > histogram.Max {
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histogram.Max = value
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}
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if value < histogram.Min {
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histogram.Min = value
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}
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histogram.Sum += value
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histogram.Count++
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for index := 0; index <= len(histogram.Bounds); index++ {
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// Allocate value in the last buckets if we reached the end of the Bounds array.
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if index == len(histogram.Bounds) {
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histogram.CountPerBucket[index]++
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break
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}
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if value < int64(histogram.Bounds[index]) {
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histogram.CountPerBucket[index]++
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break
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}
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}
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}
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// Mean returns the mean value for the histogram.
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func (histogram *HistogramData) Mean() float64 {
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if histogram.Count == 0 {
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return 0
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}
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return float64(histogram.Sum) / float64(histogram.Count)
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}
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// String converts the histogram data into human-readable string.
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func (histogram *HistogramData) String() string {
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if histogram == nil {
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return ""
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}
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var b strings.Builder
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b.WriteString("\n -- Histogram: \n")
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b.WriteString(fmt.Sprintf("Min value: %d \n", histogram.Min))
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b.WriteString(fmt.Sprintf("Max value: %d \n", histogram.Max))
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b.WriteString(fmt.Sprintf("Count: %d \n", histogram.Count))
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b.WriteString(fmt.Sprintf("50p: %.2f \n", histogram.Percentile(0.5)))
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b.WriteString(fmt.Sprintf("75p: %.2f \n", histogram.Percentile(0.75)))
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b.WriteString(fmt.Sprintf("90p: %.2f \n", histogram.Percentile(0.90)))
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numBounds := len(histogram.Bounds)
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var cum float64
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for index, count := range histogram.CountPerBucket {
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if count == 0 {
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continue
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}
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// The last bucket represents the bucket that contains the range from
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// the last bound up to infinity so it's processed differently than the
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// other buckets.
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if index == len(histogram.CountPerBucket)-1 {
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lowerBound := uint64(histogram.Bounds[numBounds-1])
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page := float64(count*100) / float64(histogram.Count)
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cum += page
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b.WriteString(fmt.Sprintf("[%s, %s) %d %.2f%% %.2f%%\n",
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humanize.IBytes(lowerBound), "infinity", count, page, cum))
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continue
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}
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upperBound := uint64(histogram.Bounds[index])
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lowerBound := uint64(0)
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if index > 0 {
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lowerBound = uint64(histogram.Bounds[index-1])
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}
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page := float64(count*100) / float64(histogram.Count)
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cum += page
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b.WriteString(fmt.Sprintf("[%d, %d) %d %.2f%% %.2f%%\n",
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lowerBound, upperBound, count, page, cum))
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}
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b.WriteString(" --\n")
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return b.String()
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}
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// Percentile returns the percentile value for the histogram.
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// value of p should be between [0.0-1.0]
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func (histogram *HistogramData) Percentile(p float64) float64 {
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if histogram == nil {
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return 0
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}
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if histogram.Count == 0 {
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// if no data return the minimum range
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return histogram.Bounds[0]
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}
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pval := int64(float64(histogram.Count) * p)
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for i, v := range histogram.CountPerBucket {
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pval = pval - v
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if pval <= 0 {
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if i == len(histogram.Bounds) {
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break
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}
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return histogram.Bounds[i]
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}
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}
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// default return should be the max range
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return histogram.Bounds[len(histogram.Bounds)-1]
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}
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// Clear reset the histogram. Helpful in situations where we need to reset the metrics
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func (histogram *HistogramData) Clear() {
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if histogram == nil {
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return
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}
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histogram.Count = 0
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histogram.CountPerBucket = make([]int64, len(histogram.Bounds)+1)
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histogram.Sum = 0
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histogram.Max = 0
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histogram.Min = math.MaxInt64
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}
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