private def evalThresholds()

in core/src/main/scala/com/spotify/featran/transformers/mdl/ThresholdFinder.scala [145:169]

• 18 lines of code
• 3 McCabe index (conditional complexity)

  private def evalThresholds(
    candidates: Seq[(Float, Array[Long])],
    lastSelected: Option[Float],
    nLabels: Int
  ): Option[Float] = {
    // Calculate the total frequencies by label
    val totals = Array.fill(nLabels)(0L)
    candidates.foreach(kv => MDLUtil.plusI(totals, kv._2))

    // Compute the accumulated frequencies (both left and right) by label
    var leftAccum = Array.fill(nLabels)(0L)
    var entropyFreqs =
      List.empty[(Float, Array[Long], Array[Long], Array[Long])]
    candidates.foreach { case (cand, freq) =>
      leftAccum = MDLUtil.plus(leftAccum, freq)
      val rightTotal = MDLUtil.minus(totals, leftAccum)
      entropyFreqs = (cand, freq, leftAccum, rightTotal) :: entropyFreqs
    }

    // select best threshold according to the criteria
    val finalCandidates = bestThreshold(entropyFreqs, lastSelected, totals)

    // Select among the list of accepted candidate, that with the minimum weightedHs
    if (finalCandidates.nonEmpty) Some(finalCandidates.min._2) else None
  }