Tony Grosinger
a1e0fb3b7e
Smudge provides an implementation of the gossip protocol that will be
used for communicating with other chat client implementations.
Retrieved at: d39c17654b
118 lines
2.7 KiB
Go
118 lines
2.7 KiB
Go
/*
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Copyright 2016 The Smudge Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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 smudge
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import (
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"math"
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"sync"
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)
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type pingData struct {
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sync.RWMutex
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// The ping data. Initialized with default values by NewPingData()
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pings []uint32
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// The index in pings where the next datapoint will be added
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pointer int
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// The last calulcated mean. Recalculated if updated is true
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lastMean float64
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// The last calulcated standard deviation. Recalculated if updated is true
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lastStddev float64
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// The modified flag. Set to true when a datapoint is added
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updated bool
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}
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func newPingData(initialAverage int, historyCount int) pingData {
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newPings := make([]uint32, historyCount, historyCount)
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for i := 0; i < historyCount; i++ {
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newPings[i] = uint32(initialAverage)
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}
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return pingData{pings: newPings, updated: true}
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}
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func (pd *pingData) add(datapoint uint32) {
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pd.Lock()
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pd.pings[pd.pointer] = datapoint
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// Advance the pointer
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pd.pointer++
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pd.pointer %= len(pd.pings)
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pd.updated = true
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pd.Unlock()
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}
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// mean returns the simple mean (average) of the collected datapoints.
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func (pd *pingData) mean() float64 {
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pd.data()
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return pd.lastMean
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}
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// Returns the mean modified by the requested number of sigmas
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func (pd *pingData) nSigma(sigmas float64) float64 {
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mean, stddev := pd.data()
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return mean + (sigmas * stddev)
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}
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// stddev returns the standard deviation of the collected datapoints
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func (pd *pingData) stddev() float64 {
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pd.data()
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return pd.lastStddev
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}
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// Returns both mean and standard deviation
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func (pd *pingData) data() (float64, float64) {
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if pd.updated {
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pd.Lock()
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// Calculate the mean
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var accumulator float64
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for _, d := range pd.pings {
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accumulator += float64(d)
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}
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pd.lastMean = accumulator / float64(len(pd.pings))
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// Subtract the mean and square the result; calculcate the mean
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accumulator = 0.0 // Reusing accumulator.
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for _, d := range pd.pings {
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diff := pd.lastMean - float64(d)
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accumulator += math.Pow(diff, 2.0)
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}
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squareDiffMean := accumulator / float64(len(pd.pings))
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// Sqrt the square diffs mean and we have our stddev
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pd.lastStddev = math.Sqrt(squareDiffMean)
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pd.updated = false
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pd.Unlock()
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}
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return pd.lastMean, pd.lastStddev
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}
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