A computer-implemented method for determining cluster centers in a first data structure, wherein the first data structure comprises a lattice structure of weight vectors that create an approximate representation of a plurality of input data points. The method can include performing a first iterative process for iteratively updating the weight vectors such that they move toward cluster centers; performing a second iterative process for iteratively updating a second data structure utilizing results of the iterative updating of the first data structure; and determining the weight vectors that correspond to cluster centers of the input data points on the basis of the second data structure.