Using Visualization Tools to Understand Concurrency

1. Using Visualization Tools to Understand Concurrency written by Zernik, Dror, Marc Snir, and Alia Malki Kim, Byung-Chul

2. Why Visualization Tool? • Parallelism • makes program execution much more complex and difficult to understand • Visualization Tool • gives a clearer picture of concurrency • helps the users grasp aspects of parallel execution more immediately and more accurately than a text interface BCKim

3. Nodes Fork Join Message send Message receive Barrier synchronization User-defined Processing Arcs Control Message Causality Graph Start Fork Fork Barrier Sync. Send Receive Join Join Terminate BCKim

4. Trace • logs each interprocess-communication and each user-defined event during execution • Time, type, processor number, process ID, and type-dependent information • logs the information into a local buffer, which is periodically copied onto disk(s). BCKim

5. a total ordering of the nodes (u => v) ordered or concurrent Serialization Order Start Fork Fork Barrier Sync. Send Receive Join Join Terminate BCKim

6. Present(u) The set of all nodes v in G that are concurrent to u including u painted red Past(u) The set of all nodes v such that v => u painted gray Future(u) The set of all nodes such that u => v painted yellow Partitioning the Graph Start Fork Fork Barrier Sync. Send u Receive Join Join Terminate BCKim

7. Initialization pick a node v and set Past, Present, and Future Incremental update Activate u Terminate u Undo u Single Stepping Forward Backward Manipulation of Graph BCKim

8. Abstraction Start Fork Fork Barrier Sync. Super node Send Receive Join Join Terminate BCKim

9. Start Fork Fork Barrier Sync. Send Receive Join Join Terminate BCKim

10. Abstraction Algorithm A directed acyclic graph and the previously selected node Abstraction Algorithm An abstraction graph by a single node BCKim

11. Branch(u) u u BCKim

12. Branch(u) u u Local Communication node BCKim

13. u BCKim

14. BCKim