Communicating Sequential Processes

A brief introduction to communicating sequential processes as a paradigm for concurrent programming.

Transcript

1. Eric Shull (@exupero) COMMUNICATING SEQUENTIAL PROCESSES
2. SHARING MEMORY THE PROBLEM: NON-DETERMINISM RACE CONDITIONS DEADLOCKS HARD TO REPRODUCE HARD TO DEBUG HARD TO ENSURE RELIABILITY
3. MUTEXES & LOCKS SEMAPHORES COMPARE & SWAP ATOMIC OPERATIONS SYNCHRONIZATION SOLUTIONS?
4. WRITE LOCK? WRITE UNLOCK. READ LOCK? FAIL! READ LOCK? DEADLOCK? GOT IT! GOT IT! COMPLEX
5. LEAKY
6. NON-COMPOSABLE
7. WANTED SIMPLICITY ABSTRACTIONS COMPOSABILITY CONCURRENCY
8. PIPESSIMPLE COMPOSABLE NON-LEAKY PARALLEL
9. CSP COMMUNICATING SEQUENTIAL PROCESSES BY C.A.R. HOARE
10. (x → P) αCTR={up, right} µX : A • F(X) (s⌒t)n+1=s⌒(t⌒s)n⌒t A* = { s | s ↾ A = s } (c?x → P(x)) = (y : { y | channel(y) = c } → P(message(y))) (c!v → P) || (c?x → Q(x)) = c!v → (P || Q(v)) (right!v → P)≫(left?y → Q(y)) = P≫Q(v) DON’T PANIC π-calculus
11. CONCEPTUAL THE MATH DEMONSTRATES SOUNDNESS
12. PROCESSES NO THREADS NO SHARED MEMORY
13. CHANNELS COMMUNICATION PASS DATA STRUCTURES VALUES AREN’T SHARED
14. ONE-TO-ONE
15. ONE-TO-MANY
16. MANY-TO-ONE
17. MANY-TO-MANY
18. SOUNDS LIKE ERLANG, EXCEPT... SYNCHRONY ... CHANNEL, NOT MAILBOX
19. CSPC.A.R. HOARE NEWSQUEAK ROB PIKE SQUEAKROB PIKE LUCA CARDELLI GO ROB PIKE KEN THOMPSON ROBERT GRIESEMER
20. CHANNELS FUNCTIONS OR GOROUTINES FUNCTIONS OR GOROUTINES NOT THREADS MIGHT HAVE MILLIONS MORE LIGHTWEIGHT GOROUTINES:
21. EXAMPLES ASYNCHRONOUS I/O EVENT COORDINATION SYNCHRONOUS I/O SHARING
22. DON’T COMMUNICATE BY SHARING MEMORY; SHARE MEMORY BY COMMUNICATING
23. CSP COMMUNICATING SEQUENTIAL PROCESSES PLAY WITH IT UNDERSTAND IT USE IT