Thank You for your suggestions
On Tue, Dec 17, 2013 at 3:19 AM, Jan van der Lugt <janl...@gmail.com> wrote: > Hi Pushparaj, > > I would not recommend doing either of these latter two approaches, since > the first one will only work for small graphs (in which case: why use a > distributed platform like Giraph?) and the second one does not give you > true random vertices. To do this efficiently, you would have to implement > it on a lower level in the Giraph stack, since the Pregel model prevents > you from doing it in another way than aggregators. Implementing this in the > WorkerContext could be slightly more efficient, but for big graphs this > would be unfeasible as well, because you are basically creating a copy of > the vertices in your graph in a way that you can access it slightly more > flexible. I think it is fair to file a JIRA to request this functionality. > > A computationally more expensive, but memory-wise more efficient way to do > this would be to have every vertex generate a random integer/long, > aggregate it to a custom MaximumAggregator (that also keeps track of a > second number that denotes the number of times the maximum occured) and > repeat this until only one vertex has picked the maximum value, but that > can take quite a few supersteps, which each require a pass over the entire > graph. > > - Jan > > > On Mon, Dec 16, 2013 at 1:11 PM, Ameya Vilankar > <ameya.vilan...@gmail.com>wrote: > >> Hi >> There are several ways of doing this. >> >> If you know you vertex Ids lie between a certain range of values like >> from 0 - (some value). Then you can simple generate a random value in that >> range and call sendMessage to send message to the randomly selected vertex. >> However, if your vertices do not lie in a certain range and you try >> sending a value to a non-existent vertex, giraph will automatically create >> the vertex(to the best of my knowledge.). >> >> A simpler way is have every vertex send its id to an aggregator and that >> will accumulate an array of all vertex ids which will be available next >> superstep to all the other vertices. Then they can randomly select a vertex >> id and send a message. But again, if you have millions of vertices , you >> would run into scalability problems with array of vertex ids growing too >> large. A simpler alternative is to send a random message to the existing >> edges of the vertex because to already have access to it. >> >> Thanks, >> Ameya. >> >> >> On Mon, Dec 16, 2013 at 7:41 AM, Pushparaj Motamari < >> pushpara...@gmail.com> wrote: >> >>> Hi, >>> >>> In a compute method I would like to send message to a random vertex, how >>> could I able to get random vertexid? >>> >>> Thanks >>> >>> Pushparaj >>> >> >> >
