Hi, I'm currently working on GIRAPH-480 to add a convergence check to RandomWalkVertex (which is an abstract version of PageRank and RandomWalkWithRestart).
RandomWalkVertex extends LongDoubleFloatDoubleEdgeListVertex which means that the edge values (the transition probabilities between the vertices) are explicitly modeled. AFAIK in most cases these probabilities are taken as uniform which means we could simply use 1 / getNumEdges() as transition probability and save a lot of space by omitting the edge values for each vertex. RandomWalkVertex could then simply extend LongDoubleNullDoubleVertex. I think this issue is pretty important, as RandomWalkVertex should be the basis for a real-world PageRank implementation (that can deal with dangling nodes and has a convergence check). Best, Sebastian PS: It's great to see how much progress Giraph has made over the last months!
