The document discusses various approaches for dealing with concurrency and parallelism in programming. It highlights that while threads and locks make concurrency difficult, there are better solutions like fork/join pools, dataflow programming, and actors. These approaches allow programmers to write code without worrying about threads and synchronization, making parallelism easier to implement. The key milestone approaches mentioned are asynchronous calculations, parallel collection processing using fork/join, dataflow programming using variables and streams, and using actors to isolate concurrent operations.

5. # of cores Today Soon

18. Tree traversal

19. File scan / search

24. No live-locks

28. df .y = 5

29. }

30. assert 15 == df .z

31. Composing async functions int hash1 = hash(download( 'http://www.gpars.org' )) int hash2 = hash(loadFile( '/gpars/website/index.html' )) boolean result = compare(hash1, hash2) println result

32. Composing async functions def hash = oldHash.asyncFun() def compare = oldCompare.asyncFun() def download = oldDownload.asyncFun() def loadFile = oldLoadFile.asyncFun() def hash1 = hash(download( 'http://www.gpars.org' )) def hash2 = hash(loadFile( '/gpars/website/index.html' )) def result = compare(hash1, hash2) println result .get()

33. Composing async functions int hash(String text ) {…} Promise<int> hash( Promise<String> | String text )

35. Wait (non-blocking) for the text param

36. Call the original hash()

37. Bind the result }

38. Composing async functions Combine functions as usual Parallelism is detected automatically

40. Fork/Join

41. Parallel collection processing

42. Dataflow variables/streams

45. Send a message

48. public void onMessage(String msg ) {

49. String encripted = encrypt( msg );

50. reply( encripted );

51. }

52. public void onMessage(Integer number ) {

53. reply(2 * number );

54. }

55. public void onMessage(Money cash ) {

56. System.out.println( &quot;Received a donation &quot; + cash );

57. account .deposit( cash );

58. }

59. }

60. Active Objects @ActiveObject class MyCounter { private int counter = 0 @ActiveMethod def incrementBy( int value) { println &quot;Received an integer: $value &quot; this .counter += value } }

63. Jon Kerridge, Napier University

66. http://www.jroller.com/vaclav

67. http://twitter.com/vaclav_pech