if acc.lastTime != math.MaxInt64 {
			// Update distribution.
			acc.mud.add(acc.lastMU, mu, float64(time-acc.lastTime))
		}
		acc.lastTime, acc.lastMU = time, mu
		if _, mudBound, ok := acc.mud.approxInvCumulativeSum(); ok {
			acc.bound = math.Max(acc.bound, mudBound)
		} else {
			// We haven't accumulated enough total precise
			// mass yet to even reach our goal, so keep
			// accumulating.
			acc.bound = 1
		}