static inline T distance()

in src/annoylib.h [571:586]

• 11 lines of code
• 6 McCabe index (conditional complexity)

  static inline T distance(const Node<S, T>* x, const Node<S, T>* y, int f) {
    if (x->built || y->built) {
      // When index is already built, we don't need angular distances to retrieve NNs
      // Thus, we can return dot product scores itself
      return -dot(x->v, y->v, f);
    }

    // Calculated by analogy with the angular case
    T pp = x->norm ? x->norm : dot(x->v, x->v, f) + x->dot_factor * x->dot_factor;
    T qq = y->norm ? y->norm : dot(y->v, y->v, f) + y->dot_factor * y->dot_factor;
    T pq = dot(x->v, y->v, f) + x->dot_factor * y->dot_factor;
    T ppqq = pp * qq;

    if (ppqq > 0) return 2.0 - 2.0 * pq / sqrt(ppqq);
    else return 2.0;
  }