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Make it harder for Mean() and StdDev() to overflow #21

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Make it harder for Mean() and StdDev() to overflow #21

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12 changes: 7 additions & 5 deletions hdr.go
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Original file line number Diff line number Diff line change
Expand Up @@ -155,14 +155,15 @@ func (h *Histogram) Mean() float64 {
if h.totalCount == 0 {
return 0
}
var total int64
var mean float64
totalCount := float64(h.totalCount)
i := h.iterator()
for i.next() {
if i.countAtIdx != 0 {
total += i.countAtIdx * h.medianEquivalentValue(i.valueFromIdx)
mean += float64(i.countAtIdx*h.medianEquivalentValue(i.valueFromIdx)) / totalCount
}
}
return float64(total) / float64(h.totalCount)
return mean
}

// StdDev returns the approximate standard deviation of the recorded values.
Expand All @@ -173,16 +174,17 @@ func (h *Histogram) StdDev() float64 {

mean := h.Mean()
geometricDevTotal := 0.0
totalCount := float64(h.totalCount)

i := h.iterator()
for i.next() {
if i.countAtIdx != 0 {
dev := float64(h.medianEquivalentValue(i.valueFromIdx)) - mean
geometricDevTotal += (dev * dev) * float64(i.countAtIdx)
geometricDevTotal += (dev * dev) * float64(i.countAtIdx) / totalCount
}
}

return math.Sqrt(geometricDevTotal / float64(h.totalCount))
return math.Sqrt(geometricDevTotal)
}

// Reset deletes all recorded values and restores the histogram to its original
Expand Down