* outputFuture is the future we return to the caller, a nonCancellationPropagating taskFuture.
     *
     * newFuture is guaranteed to only complete once all tasks previously submitted to this instance
     * have completed - namely after oldFuture is done, and taskFuture has either completed or been
     * cancelled before the callable started execution.
     */
    SettableFuture<@Nullable Void> newFuture = SettableFuture.create();

    // it. We swap the pivot into partitionPoint and we know the array is partitioned around that.
    swap(array, from, partitionPoint);
    return partitionPoint;
  }

  /**
   * Selects the pivot to use, namely the median of the values at {@code from}, {@code to}, and
   * halfway between the two (rounded down), from {@code array}, and ensure (by swapping elements if