(loop named convergence
      for iteration from 0 to iteration-limit
      do (loop for document in documents
               for old-rank = (rank document)
               for new-rank = (loop for neighbor in (graph-neighbors document)
                                    sum (/ (* damping (rank neighbor) (document-similarity document neighbor))
                                           (graph-neighbor-edge-sum neighbor)))
               do (setf (rank document) new-rank)
               when (convergedp old-rank new-rank)
                 do (return-from convergence)))