Major Description
SparkGraphComputer input RDDs are typed as:
JavaPairRDD<Object,VertexWritable>
The VertexWritable usage is a vestige from Hadoop and Giraph. In Spark, we don't need to have this wrapper and thus, we can reduce the overhead (one less object header) by making the input RDDs typed as:
JavaPairRDD<Object,StarGraph>
This would be a breaking change for graph providers that implement their own InputRDD and OutputRDD, however, the fix is trivial. Instead of new VertexWritable(vertex), they would simply do StarGraph.of(vertex).