code: @Override
      protected int msd(Long a, Long b) {
          /*
           * Value equal
           */
          if (a.longValue() == b.longValue()) {
              return -1;
          }
          /*
           * This is a fast way to compute floor(log_2(a xor b)).
           */
          double axorb = a ^ b;
          return Math.getExponent(axorb);
      }
docs: {@inheritDoc}