1. Definitions & Scenarios

2. Acknowledgements  This tutorial is based in part on Concurrency: State Models & Java Programming by Jeff Magee and Jeff Kramer.

3. Acknowledgements  Tutorial Authors/Creators: Zhen Li, Eileen Kraemer, Zhe Zhao Computer Science Department The University of Georgia

4.  Concurrent Program  Process & Thread  Thread Life Cycle

5. Sequential v. Concurrent  Programs consist of subprograms or procedures simpler sets of activities that together make up the overall program  Sequential program Subprograms are executed one after the other in fixed order, determined by program’s input  Concurrent program The execution of subprograms may overlap in time

6.  Computational activities that overlap in time may occur in parallel, or be interleaved. Concurrent Program Parallelism Interleaved

7.  In a concurrent program, computational activities are permitted to overlap in time. Concurrent Program Parallelism Interleaved

8.  In a concurrent program, computational activities are permitted to overlap in time. Concurrent Program Parallelism Interleaved

9. Process  The execution of a sequential program or subprogram  A unit of sequential execution  A concurrent program consists of multiple processes.

10. Process Parallelism Interleaved Three processes in each figure

11. Thread  A method of implementing concurrency Parallelism Interleaved Two different implementations

12. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield suspend resume alive

13. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

14. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

15. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

16. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

17. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

18. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

19. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

20. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop dispatch yield resume alive suspend

21. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop dispatch yield resume alive suspend

22. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

23. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop yield resume alive suspend

24. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop yield resume alive suspend

25. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

26. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch resume alive suspend

27. Thread Life Cycle createdterminated Ready (Runnable) Waiting (Non-runnable) stop startstop dispatch resume alive suspend running

28. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

29. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive

30. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive

31. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

32. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield alive suspend

33. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield alive suspend

34. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

35. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

36. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive

37. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive

38. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

39. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop start dispatch yield resume alive suspend

40. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop start dispatch yield resume alive suspend

41. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop dispatch yield resume alive suspend

42. Thread Life Cycle created terminated Ready (Runnable) running Waiting (Non-runnable) stop dispatch yield resume alive suspend

43. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop dispatch yield resume alive suspend

44. Thread Life Cycle createdterminated Ready (Runnable) running Waiting (Non-runnable) stop startstop dispatch yield resume alive suspend

45.  Shared Objects  Conditional Synchronization  Resource Allocation

46. Shared Object  Multiple threads have computational activities on the same object  Ornamental Garden Garden East Turnstile West Turnstile

47. A Naïve Implementation Garden East Turnstile West Turnstile population thread shared object

48. A Naïve Implementation

49. Problem

51. Race Condition  A common flaw in implementing a concurrent program with shared objects  Final results depend on the execution sequence of threads  Therac-25 accident

52. Mutual Exclusion  Access to shared objects should be mutually exclusive in time

53. Solution  Lock for atomic operation

54. Solution  Lock for atomic operation

56. Review  Definitions Concurrency Process & Thread Thread Life Cycle  Scenarios Shared Objects – Race Conditions