int oneBased = ~~(index + 1); // for GWT
    checkState(oneBased > 0, "negative index");
    return (oneBased & EVEN_POWERS_OF_TWO) > (oneBased & ODD_POWERS_OF_TWO);
  }

  /**
   * Returns {@code true} if the MinMax heap structure holds. This is only used in testing.
   *
   * <p>TODO(kevinb): move to the test class?
   */
  @VisibleForTesting
  boolean isIntact() {
    for (int i = 1; i < size; i++) {