1. A computer implemented method, the computer comprising a processor and memory, the method comprising: projecting an n-dimension space Θ with a dissimilarity measure μ into an m-dimensional space P with a dissimilarity measure μ′ by a projection function p, wherein: 1<m<n; and μ′ (p(v 1 ), p(v 2 ))≦μ(v 1 , v 2 ) for all points v 1 and v 2 in Θ; selecting a point v in Θ; performing a search in P for a set S′ of k nearest neighbors of the point p(v) in P; finding a set S of all points in Θ that project to the set S′; and determining whether a point of the set S is a nearest neighbor of the point v.