Hi Kyle, combiners are set by the user, as you recognized, and called automatically by the infrastructure at different moments in the path. Combined messages are passed transparently to the compute method (namely less messages than a vertex would have received without a combiner). Have a look at the PageRank examples and benchmark code.
Best, Claudio On Tue, Aug 20, 2013 at 8:51 PM, Kyle Orlando <kyle.r.orla...@gmail.com>wrote: > Hey all, > > I was wondering if there was any example code I could look at that uses a > combiner. Creating your own Combiner is easy enough, e.g. > DoubleSumCombiner, but I am confused as to how/where I would use the > classes in my code. > > For example, say I wanted to utilize the DoubleSumCombiner class to sum up > all of the messages arriving at a particular vertex at the beginning of the > superstep, and I wanted to do this for each vertex in the graph. Where > should I instantiate a DoubleSumCombiner, when should I call the combine() > and createInitialMessage() methods, etc. in the compute() method? > > What further confuses me is that I see that the MasterCompute class has > methods for setCombiner() and getCombiner(), and that there is also a > command line option -c to specify a Combiner. I'm not really sure if these > are even necessary, but if they are, I don't know how these come into play > either. > > Some clarification or direction towards an example would be nice! > > Thanks, > -- > Kyle Orlando > Computer Engineering Major > University of Maryland > -- Claudio Martella claudio.marte...@gmail.com
