Github user mtustin-handy commented on a diff in the pull request: https://github.com/apache/spark/pull/11982#discussion_r57529573 --- Diff: core/src/main/scala/org/apache/spark/partial/SumEvaluator.scala --- @@ -56,9 +56,12 @@ private[spark] class SumEvaluator(totalOutputs: Int, confidence: Double) val confFactor = { if (counter.count > 100) { new NormalDistribution().inverseCumulativeProbability(1 - (1 - confidence) / 2) - } else { + } else if (counter.count > 1) { val degreesOfFreedom = (counter.count - 1).toInt new TDistribution(degreesOfFreedom).inverseCumulativeProbability(1 - (1 - confidence) / 2) + } else { + // No way to meaningfully estimate confidence, so we signal no particular confidence interval + Double.PositiveInfinity --- End diff -- Look out for updates to this tomorrow (Eastern Time; so probably we'll loop back on this Tuesday).
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