add range_search() to IndexRefine

[alexanderguzhva]

This is very convenient to have range_seach() in IndexRefine. Unlike the plain search() method, range_search() just reevaluates the computed distances from the baseline index. The labels are not re-sorted according to new distances, because this is not listed as a requirement in a method description

faiss/faiss/Index.h

Lines 150 to 161 in adb1884

	/** query n vectors of dimension d to the index.
	*
	* return all vectors with distance < radius. Note that many
	* indexes do not implement the range_search (only the k-NN search
	* is mandatory).
	*
	* @param n number of vectors
	* @param x input vectors to search, size n * d
	* @param radius search radius
	* @param result result table
	*/
	virtual void range_search(

faiss/faiss/impl/AuxIndexStructures.h

Line 35 in adb1884

float* distances; ///< corresponding distances (not sorted)