static inline T distance()

in src/annoylib.h [475:485]

• 8 lines of code
• 4 McCabe index (conditional complexity)

  static inline T distance(const Node<S, T>* x, const Node<S, T>* y, int f) {
    // want to calculate (a/|a| - b/|b|)^2
    // = a^2 / a^2 + b^2 / b^2 - 2ab/|a||b|
    // = 2 - 2cos
    T pp = x->norm ? x->norm : dot(x->v, x->v, f); // For backwards compatibility reasons, we need to fall back and compute the norm here
    T qq = y->norm ? y->norm : dot(y->v, y->v, f);
    T pq = dot(x->v, y->v, f);
    T ppqq = pp * qq;
    if (ppqq > 0) return 2.0 - 2.0 * pq / sqrt(ppqq);
    else return 2.0; // cos is 0
  }