Partition Function
In Hama BSP computing framework, the Partition function is used for obtaining scalability of a Bulk Synchronous Parallel processing, and determining how to distribute the slices of input data among BSP processors. Unlike Map/Reduce data processing model, many scientific algorithms based on Message-Passing Bulk Synchronous Parallel model often requires that a processor obtain “nearby or related” data from other processors in order to complete the computation. In this case, you can create your own Partition function for determining processor inter-communication and how to distribute the data.
Internally, Input data-partitioning works as following sequence:
- If user specified partition function, internally, "partitioning job" is ran as a pre-processing step.
- Each task of "partitioning job" reads its assigned data block and rewrite them to particular partition files.
- Job Scheduler assigns partitions to proper task based on partition ID.
- After prepartitioning done, launch the BSP job.
Create your own Partitioner
Partitioner Configuration
BSPJob job = new BSPJob(conf); ... job.setPartitioner(HashPartitioner.class); ...