360|iDev Concurrency Workshop

Transcript

1. Concurrency workshop Sam Davies @iwantmyrealname _ github.com/sammyd
 git.io/v6waD

2. concurrency is hard

3. what is concurrency?

4. why use concurrency?

5. common concurrency problems

6. race condition

7. Race Condition time Value 1 Thread 1 Thread 2 inc

8. Race Condition time Value 1 1 Thread 1 Thread 2

   inc r1

9. Race Condition time Value 1 1 1 Thread 1 Thread

   2 inc r1 +1

10. Race Condition time Value 1 1 1 2 Thread 1

    Thread 2 inc r1 w2 +1

11. Race Condition time Value 1 1 1 2 2 Thread

    1 Thread 2 inc r1 w2 +1 inc

12. Race Condition time Value 1 1 1 2 2 2

    Thread 1 Thread 2 inc r1 w2 +1 inc r2

13. Race Condition time Value 1 1 1 2 2 2

    2 Thread 1 Thread 2 inc r1 w2 +1 inc r2 +1

14. Race Condition time Value 1 1 1 2 2 2

    2 3 Thread 1 Thread 2 inc r1 w2 +1 inc r2 w3 +1

15. Race Condition time Value 1 Thread 1 Thread 2 inc

16. Race Condition time Value 1 1 Thread 1 Thread 2

    inc r1 inc

17. Race Condition time Value 1 1 1 Thread 1 Thread

    2 inc r1 inc r1

18. Race Condition time Value 1 1 1 1 Thread 1

    Thread 2 inc r1 inc r1 +1

19. Race Condition time Value 1 1 1 2 1 Thread

    1 Thread 2 inc r1 inc r1 w2 +1

20. Race Condition time Value 1 1 1 2 1 2

    Thread 1 Thread 2 inc r1 +1 inc r1 w2 +1

21. Race Condition time Value 1 1 1 2 1 2

    2 Thread 1 Thread 2 inc r1 w2 +1 inc r1 w2 +1

22. priority inversion

23. Priority Inversion time low priority resource

24. Priority Inversion time low priority resource

25. Priority Inversion time low medium priority resource

26. Priority Inversion time low medium high priority resource

27. Priority Inversion time low medium high priority resource

28. Priority Inversion time low medium high priority resource

29. Priority Inversion time low medium high priority resource

30. deadlock

31. Deadlock time resource1 resource2 Thread 1 Thread 2

32. Deadlock time resource1 resource2 Thread 1 Thread 2

33. Deadlock time resource1 resource2 Thread 1 Thread 2

34. Deadlock time resource1 resource2 Thread 1 Thread 2

35. Deadlock time resource1 resource2 Thread 1 Thread 2

36. Deadlock time resource1 resource2 Thread 1 Thread 2

37. Deadlock time resource1 resource2 Thread 1 Thread 2

38. Deadlock time resource1 resource2 Thread 1 Thread 2

39. $&'( queueueueueue paradigm

40. Tasks & Queues Thread 1 Thread 2 Queue

41. Tasks & Queues Thread 1 Thread 2 Queue

42. Tasks & Queues Thread 1 Thread 2 Queue

43. Tasks & Queues Thread 1 Thread 2 Queue

44. Tasks & Queues Thread 1 Thread 2 Queue

45. Tasks & Queues Thread 1 Thread 2 Queue

46. Tasks & Queues Thread 1 Thread 2 Queue

47. feeling brave?

48. a touch more theory

49. Thread Safety time Value 1111 Thread 1 Thread 2 Thread

    3

50. Thread Safety time Value 1111 Thread 1 Thread 2 r1111

    Thread 3

51. Thread Safety time Value 1111 1112 Thread 1 Thread 2

    r1111 w2222 Thread 3

52. Thread Safety time Value 1111 1112 1122 Thread 1 Thread

    2 r1111 w2222 r1122 Thread 3

53. Thread Safety time Value 1111 1112 1122 1223 Thread 1

    Thread 2 r1111 w2222 r1122 w3333 Thread 3 r1223

54. Thread Safety time Value 1111 1112 1122 1223 2233 Thread

    1 Thread 2 r1111 w2222 r1122 w3333 Thread 3 r1223

55. Thread Safety time Value 1111 1112 1122 1223 2233 2333

    Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223

56. Thread Safety time Value 1111 1112 1122 1223 2233 2333

    3333 Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223

57. Thread Safety time Value 1111 1112 1122 1223 2233 2333

    3333 3333 3333 Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223 r3333 r3333

58. Dispatch Barrier time task task task task task barrier task

    task task task task task task task

59. Dispatch Barrier time read read read read read read write

    read read read read read read

60. alternatives to 

61. promises networkRequest(url, callback: { data in decompressor(data, callback: { image

    in imageResizer(image, callback: { small in filterImage(small, callback: { filtered in displayImage(filtered) }) }) }) })

62. promises promise<int> int error

63. promises str

64. promises promise<img> str f

65. promises promise<img> str error f img

66. promises promise<img> str error f img error handler

67. promises promise<img> str error f img g promise<img> error handler

68. promises promise<img> str error f img g promise<img> error error

    handler img

69. promises promise<img> str error f img g promise<img> error error

    handler img

70. promises networkRequest(url) .then(decompressor) .then(imageResizer) .then({ (image) in return filterImage(image) }).then(displayImage)

    .catch({ (error) in print(error) })

71. imagine the “promise pipeline” accepted a sequence of values…

72. that’s reactive programming

73. conclusion

74. concurrency is hard

75. you will get it wrong

76. • raywenderlich.com/videos • git.io/v6waD • @iwantmyrealname