I have a Graph processing problem where after each iteration, some vertices get vanished. That is, they get merged into their neighbouring nodes based on certain conditions and the graph keeps getting simplified after each iteration.

I was wondering if Giraph is worth trying for this.

I was going through the documentation and it says that the input data has to be sorted.Why is this necessary?

Also, how does the so called 'master' divide vertices in ranges? Does it use some kind of a range partitioner? If there is range partitioning, that's a problem for me, because of vanishing vertices - there will be load imbalance.

Best,

Deepak