Cache Friendly Parallel Priority Queue

1. Cache Friendly Parallel Priority Queue Dinesh Agarwal Distributed Mobile Systems Lab (DiMoS)

2. Overview • Parallel Priority Queue • Task Allocation Strategies • Prefetching • Experimental Results

3. Parallel Priority Queue • Parallel Binary Heap • r elements per node • Parallel Heap Property • Top priority r items at root • General (worker) Processors • Maintenance Processors

4. Parallel Priority Queue

5. Task Allocation Strategies • Round Robin • After updating current level, a processor i jumps to Xthlevel; X =(current level + 2 * processors) • Blocking • After updating current level, a processor jumps to Xth level; X = (current level + 2) • Round Robin with Shift • Processor starts working at a level it worked on during last iteration

6. Prefetching • Observation: To update a node you need its children nodes • Prediction: If the next node to be operated on is known, so are the children • Touch the memory blocks where the children are stored • Overlap these memory reads with work

7. Experimental Results • Speedup for varying granularity:

8. Experimental Results • Performance for varying n

9. Experimental Results • Speedup for varying r:

10. Experimental Results • Performance on different Machines:

11. Experimental Results • Prefetching:

12. Experimental Results • Allocation Strategies: