1) The document discusses concurrency and the traditional model of sharing data between threads which leads to complexity, bugs, and diminishing returns. 2) It introduces the actor model from 1973 which uses message passing between isolated processes or "actors" to achieve concurrency without shared data. 3) ZeroMQ is presented as a modern implementation of the actor model, allowing applications to connect threads and processes across machines using messaging without locks or shared state.

1. Multithreading Magic Why Everything You Thought You Knew about Concurrency is Bogus, if not actually Totally Insane by Pieter Hintjens, CEO, iMatix FOSDEM 2011

2. Hintjens' Law of Concurrency e = mc 2 e is for effort , the pain that it takes

3. m is for mass , the size of the code

4. c is for conflict , when c threads collide

5. The Cost of Concurrency Where we end up Where we start

6. The Data-Centric Model Thread Thread Thread Thread The industry standard model for concurrency, based on the Big Iron computing model

7. What You (Probably) Know Concurrency = data shared between threads

8. So, locks, semaphores, critical sections

9. So, code that fails by default

10. So, complexity, weird bugs, race conditions

11. Diminishing returns as c exceeds ' a few '

12. A bogus, if not totally insane model

13. The Ideal World Where we end up Where we start

14. What You (Probably) Don't Know The Actor Model Carl Hewitt, 1973, " Motivated by the prospect of thousands of independent microprocessors, each with its own local memory, communicating via a high-performance network .” – Wikipedia

15. Gives us concurrency with c = 1 For 30 years, mostly ignored Distributed systems were too small and rare

16. Maybe best known via Erlang

17. Boxes, sending messages A better match for a world filled with CPUs Box Messages

18. Ingredients Lots of cheap boxes – check! Thousands of threads, processes, cores, systems Messages as contractual APIs – check! XML, YAML, JSON, etc.

19. Any level of meta we want A high-performance network? Brings us to ZeroMQ

20. Cheap and fast networking – check!

21. ZeroMQ: e = mc 2 , for c = 1 Zero shared data – a modern Actor model

22. Connect threads, processes, boxes The same socket-style API for any transport Add any message contracts you want ZeroMQ transports blobs Connect tasks using messaging patterns Request-reply, pub-sub, pipeline,...

23. Your ZeroMQ Applications Any mix of languages and platforms

24. No locks, semaphores, critical sections Each task has its state

25. Process incoming messages from all sources

26. Send onward messages to other tasks Scale to any number of cores Threads or processes on one box

27. Multiple boxes on one network

28. Get ZeroMQ http://www.zeromq.org

29. Free software, LGPL licensed

30. In continuous development since 2007

31. Large, active community (~70 people on IRC)

32. APIs in C, C++, Python, Ruby, Perl, Java, Go, Erland, C#, PHP, Lua, Clisp, Haskell,...

33. Linux, UNIX, OS/X, Windows,...

34. About iMatix Messaging, free software, communities

35. In 2010 we turned ZeroMQ fully over to its community (which we are part of :-)

36. Our business is commercial support for companies using ZeroMQ in infrastructure projects

37. Contact me at [email_address]