return at most k vectors. If there are not enough results for a
query, the result array is padded with -1s.
@param index opaque pointer to index object
@param x input vectors to search, size n * d
@param labels output labels of the NNs, size n*k
@param distances output pairwise distances, size n*k
query n vectors of dimension d to the index.
return at most k vectors. If there are not enough results for a query, the result array is padded with -1s.
@param index opaque pointer to index object @param x input vectors to search, size n * d @param labels output labels of the NNs, size n*k @param distances output pairwise distances, size n*k