*/
fun formatDuration(ns: Long): String {
  val s =
    when {
      ns <= -999_500_000 -> "${(ns - 500_000_000) / 1_000_000_000} s "
      ns <= -999_500 -> "${(ns - 500_000) / 1_000_000} ms"
      ns <= 0 -> "${(ns - 500) / 1_000} µs"
      ns < 999_500 -> "${(ns + 500) / 1_000} µs"
      ns < 999_500_000 -> "${(ns + 500_000) / 1_000_000} ms"
      else -> "${(ns + 500_000_000) / 1_000_000_000} s "
    }