1. An apparatus comprising: a processor programmed to compare a first object comprising or represented by a first set of vectors in a vector space and a second object comprising or represented by a second set of vectors in the vector space by a comparison method comprising: computing a first signature based on distribution of the vectors of the first set of vectors over a set of regions of the vector space wherein statistics of the vectors of the first set of vectors in the regions are represented in the first signature by values including binary values, computing a second signature based on distribution of the vectors of the second set of vectors over the set of regions of the vector space wherein statistics of the vectors of the second set of vectors in the regions are represented in the second signature by values including binary values, and computing a vector set comparison measure based on the first signature and the second signature.