Back in the old days of "Eigenfaces", you could project faces into 12- or 13-dimensional space using SVD and do k-nearest-neighbor. This fit into cache even bac

Back in the old days of "Eigenfaces", you could project faces into 12- or 13-dimensional space using SVD and do k-nearest-neighbor. This fit into cache even back in the 90s, at least if your faces were pre-cropped to (say) 100x100 pixels.