return the indexes of the k vectors closest to the query x.
This function is identical as search but only return labels of neighbors.
@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
return the indexes of the k vectors closest to the query x.
This function is identical as search but only return labels of neighbors. @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