1. Parallel LTL Model Checking CS 586

2. The Capacity Problem Capacity = memory states*stateSize Increase capacity by - Increasing memory - Decreasing states - Decreasing state size

3. Double DFS in Parallel Memory available in one machine Memory needed to store visited states

4. DDFS Search order A B C If the dfs2 from A visits C first, then the dfs2 from B will not visit C and will not detect a cycle. Solutions?

5. Solution Ideas Use a different algorithm. Schedule the dfs2 searches Use different bits to mark dfs2 visits ______ ?

6. One Idea Forget about proving correctness. Each search process is random. Coordinate efforts to find cycles. Coordination scheme should be.. Decentralized Fault-tolerant Better than no coordination at all

7. Forager Allocation Problem Given: several foraging sites with varying quality the current needs of the hive a pool of foragers Allocate the foragers to: maximize the collection of needed resources Without central control.

8. Scouts locate patches

9. Scouts multicast their findings Scout performs a waggle dance which is observed by unemployed foragers. Duration and intensity of the dance describe the quality of the patch.

10. Workers visit patches. A worker will observe a dance and leave for a patch. Returns, unloads and dances. May visit patch again.

11. Adaptation Apis Mellifera Bee forager Search flight pattern Flower patch Pollen Waggle dance BEE (bee-based error explorer) Search agent Random walk Accept state Property Violation Multicast

12. Decentralized Cooperative Search A B C Launch n random searches. When one finds an accept state, advertize its location. Listen to and possibly ignore advertizements.

13. BEE Search controller BEE distribute problem

14. BEE Search controller multicast an accept state

15. BEE Search controller more multicasts report an error

16. BEE Search controller search continues…

17. BEE Search controller search terminated

18. Experimental Environment Classroom laboratory workstations Lowest priority level 8 MB of RAM per machine Compare with isolated parallel random walks to measure advantage of coordination.

19. Speedup-SS7

20. Speedup-11peterson

22. Too Much Communication SS 7 11 Peterson

25. ACCEPT STATE FORAGING time to receive cycle advertisement recruit to cycle foraging abandon accept state foraging WATER COLLECTING water in hive recruiting to water collecting (waggle dance) abandoning of water collecting water seeking by receiver bees time to find an unloader evaporative cooling Negative Feedback