docs: public static double dotDense(NumberVector v1, NumberVector v2) {
      final int dim1 = v1.getDimensionality(), dim2 = v2.getDimensionality();
      final int mindim = (dim1 <= dim2) ? dim1 : dim2;
      double dot = 0;
      for(int k = 0; k < mindim; k++) {
        dot += v1.doubleValue(k) * v2.doubleValue(k);
      }
      return dot;
    }