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Embracing Concurrency: For Fun, Utility & Simpler Code (Michael Sparks)
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Embracing Concurrency: For Fun, Utility & Simpler Code (Michael Sparks)


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  • 1. Embracing Concurrency for Fun, Utility & Simpler CodeMichael SparksBBC R&D, Ignite Leeds, Jan 2009
  • 2. Embracing Concurrency for Fun, Utility & Simpler Code Or “what weve learnt as a part of the Kamaelia project about making concurrency something thats fun and useful, and usable by novice and advanced developers alike... ...rather than a pain in the neck”Michael SparksBBC R&D, Ignite Leeds, Jan 2009
  • 3. Why? Hardware finally going Opportunity! massively concurrent ... .... PS3, high end servers, trickling down to desktops, laptops)“many hands make lightwork” but Viewed as Hard... do we just have crap tools? “And one language to in Problems the darkness bind them” ... can just we REALLY abandon 50 years of code for Erlang, Haskell and occam?Michael SparksBBC R&D,
  • 4. Were Taught Wrong Fundamental Control Structures ... in imperative languages number greater than 3! Control Structure Traditional Abstraction Biggest Pain Points Sequence Function Global Var Selection Function Global Var Iteration Function Global Var Parallel Thread Shared Data Usually Skipped Lost or duplicate update are most common bugsMichael SparksBBC R&D,
  • 5. Desktop gsoc Media Novice APPS trainee Network 3rd PartyMichael SparksBBC R&D,
  • 6. Speak n WriteThink backend P2P Whiteboard Programmingneeded for Simple ER DB Modeller (logo) P2P Radio Kids Gamesyoutube/flickr Torrent 3D Systemstype systems Compose Realtime Music UGC Desktop gsoc Paint App Backend P2P Web Server Secure “phone” Transcoder Social Net Vis Media Novice ...Shot ChangeDetection APPS trainee MiniAxon ScriptReader Mobile DVB MediaPreview Reframing on Mobile Reliable Macro Podcasts Network 3rd Party Multicast Sedna “record everything” XMPP XMLDB Email & AWS pubsub Spam Web (Amazon) SMTP IRC Qt Serving Gtk Greylisting Pop3Proxy ClientSide AIM microblogging Spam ToolsMichael SparksBBC R&D,
  • 7. Core Approach: Concurrent things with comms points Generally send messages Keep data private, dont share outbox inbox outbox inbox signal control signal control ... ... ... ...Michael SparksBBC R&D,
  • 8. But I must share data?Use Software Transactional Memoryie version control for variables. 1. Check out the collection of values you wish to work on 2. Change them 3. Check them back in 4. If conflict/clash, go back to 1Michael SparksBBC R&D,
  • 9. Perspectives in APIs! (1/2) st nd rd 1 , 2 , 3 Person 1st Person - I change my state2nd Person – YOU 3rd Person –want to me to do Bla shouldsomething do something(you send outbox (I send a message) inboxme a message) control signal ... ...Michael SparksBBC R&D,
  • 10. Perspectives in APIs! (2/2) st nd rd 1 , 2 , 3 Person private real methods Messages Messages sent from public to public outboxes inboxes inbox outbox control signalAlso, think ... ... Also, thinkabout stdin about stdoutMichael SparksBBC R&D,
  • 11. Actor Systems Distinction can be unclear, potential source of ambiguity* private real methods Messages from public No outbox concept inboxes Possible issues with inbox rate limiting* control Hardcodes recipient ... in the sender*system dependent issueMichael SparksBBC R&D,
  • 12. Advantages of outboxes No hardcoding of recipient allows: - Late Binding - Dynamic rewiring inbox outbox Concurrency Patterns as control signal Reusable Code ... ... ... a concurrency DSLMichael SparksBBC R&D,
  • 13. A Core Concurrency DSL Pipeline(A,B,C) Graphline(A=A,B=B, C=C, linkages = {}) Tpipe(cond, C) Seq(A,B,C), PAR(), ALT() Backplane(“name”), PublishTo(“name”), SubscribeTo(“name”) Carousel(...) PureTransformer(...) StatefulTransformer(...) PureServer(...) MessageDemuxer(...) Source(*messages) NullSink Some of these are work in progress – theyve been identified as useful, but not implemented as chassis, yetMichael SparksBBC R&D,
  • 14. Pipeline Example Pipeline( MyGamesEventsComponent(up="p", down="l", left="a", right="s"), BasicSprite("cat.png", name = "cat", border=40), ).activate() MyGames Events Component Basic SpriteMichael SparksBBC R&D,
  • 15. Graphline Example Graphline( NEXT = Button(...), PREVIOUS = Button(...), PREVIOUS NEXT FIRST = Button(...), (button) (button) LAST = Button(...), CHOOSER = Chooser(...), IMAGE = Image(...), FIRST LAST (button) (button) ... ).run() Chooser ImageMichael SparksBBC R&D,
  • 16. Server Example data from user data Main Socket handler Server Core to user Created at runtime to handle the Protocol Handler Factory connection Remote Protocol handler UserMichael SparksBBC R&D,
  • 17. Server Example You therefore need to provide Main this bit. Server Core Protocol Handler FactoryMichael SparksBBC R&D,
  • 18. Server Example from Kamaelia.Chassis.ConnectedServer import ServerCore from Kamaelia.Util.PureTransformer import PureTransformer def greeter(*argv, **argd): return PureTransformer(lambda x: "hello" +x) class GreeterServer(ServerCore): protocol=greeter port=1601 GreeterServer().run()Michael SparksBBC R&D,
  • 19. Backplane Example # Streaming Server for raw DVB of Radio 1 Backplane(“Radio”).activate() Pipeline( DVB_Multiplex(850.16, [6210], feparams), # RADIO ONE PublishTo("RADIO"), ).activate() def radio(*argv,**argd): return SubscribeTo(“RADIO”) ServerCore(protocol=radio, port=1600).run()Michael SparksBBC R&D,
  • 20. Thank you for listening! If you have questions, grab me later :-)Michael SparksBBC R&D,