Post on 15-Jan-2015
description
CONCURRENCY:RUBIES, PLURAL
Elise Huard - RubyAndRails 2010Thursday 21 October 2010
MULTIPROCESSOR/MULTICORE
Thursday 21 October 2010
NETWORK ON CHIP(50..96..100 CORES)
Thursday 21 October 2010
“... for the first time in history, no one is building a much faster sequential processor. If you want your programs to run significantly faster (...) you’re going to have to parallelize your program.”
Hennessy and Patterson “Computer Architectures” (4th edition, 2007)
Thursday 21 October 2010
But ...forget all that
(mostly)
Thursday 21 October 2010
language VM
OS(kernel processes, other processes)
Your program
multicore - multiCPU
Thursday 21 October 2010
Concurrent programs!=
Parallel computing
Thursday 21 October 2010
Thursday 21 October 2010
Thursday 21 October 2010
Scheduling
• preemptive -> thread is told to yield (by kernel or other thread)
• cooperative -> thread yields control
Thursday 21 October 2010
Processes, Threads
Process 2
RAMmemory space
Process 1
thread1
scheduler (OS)
CPU CPU
memory space
thread2 t1 t2 t3
Thursday 21 October 2010
Ruby
• Process
• Thread - green in MRI 1.8, native threads in MRI 1.9, Rubinius, JRuby
Thursday 21 October 2010
MRI: GIL
• only one thread is executed at a time
• fair scheduling: timer thread!
(10 μs for Linux, 10 ms for Windows)
• blocking region to allow limited concurrency
Thursday 21 October 2010
MRI: GIL
from http://www.igvita.com/2008/11/13/concurrency-is-a-myth-in-ruby/ @igrigorik
Thursday 21 October 2010
Other Rubies
• @evanphx working on removing the GIL on Rubinius (Hydra branch)
• JRuby, IronRuby, MacRuby don’t have GIL
Thursday 21 October 2010
Parallel quicksort
[5, 3, 22, 12, 15, -112, 6]
[-122, 5, 3, 6] [22, 15]
[-122] [5, 6]
12
3
Thursday 21 October 2010
multiprocess
•advantage: separate state
•disadvantage: overhead to spawning + context switching
Thursday 21 October 2010
Ruby: multiprocess
•fork and IPC: IO.pipe, Mmap, ...
•DRb
Thursday 21 October 2010
def execute(&block) rd, wr = IO.pipe # to retrieve results pid = fork do rd.close result = block.call wr.write result.to_json wr.close end wr.close sorted = JSON.parse(rd.read) rd.close Process.waitpid(pid) sorted end
Ruby: multiprocess
Thursday 21 October 2010
Threads
Shared state:
Mutex
ConditionVariable (semaphore)
MonitorMixin, Sync_m
Thursday 21 October 2010
Ruby threads def execute(&block) sorted = nil thread = Thread.new do sorted = block.call end thread.join sorted end
Thursday 21 October 2010
Fibers
• cooperative scheduling
• coroutines
• for MRI: lightweight
• JRuby, Rubinius: Fiber mapped to native thread
Thursday 21 October 2010
Ruby: Coroutinesrequire 'fiber'
# coroutinesary = []f2 = nilf1 = Fiber.new{ puts "please give your login" login = f2.transfer puts login puts "give password" pass = f2.transfer puts pass f2.transfer f2.transfer('***** no cigar *****')}f2 = Fiber.new{ f1.transfer('johndoe') f1.transfer('ultrasecret') answer = f1.transfer puts answer}
f1.resume vaguely inspired by http://sheddingbikes.com/posts/1287306747.html
output:please give your loginjohndoegive passwordultrasecret***** no cigar *****
Thursday 21 October 2010
MVM
Rubinius (2008): no parallel execution of threads in one VM ... so let’s create one VM per native thread
vm = Rubinius::VM.spawn "blah", "-e", "puts 'hello\n'"
Thursday 21 October 2010
Thursday 21 October 2010
shared state: will melt your brain
• non-determinism
• atomicity
• deadlock
• livelock
• fairness/starvation
• race conditions
Thursday 21 October 2010
actor model
• named actors: have no shared state
• asynchronous message passing (fire and forget)
Thursday 21 October 2010
CSP
• member of family of Process Calculi (mathematical theory)
• events, processes
• synchronous (rendez-vous) message passing
• named channels - dual to Actor model
Thursday 21 October 2010
Concurrency oriented languages
• Erlang (Actors)
• Clojure
• Go (CSP)
• Haskell (several)
• Scala (Actors)
• ...
Thursday 21 October 2010
Ideas
• functional programming: side effect free function calls
- immutable data
• nothing shared (advantage: distributed = local)
• message passing
Thursday 21 October 2010
erlang
• Actor model: Actors, asynchronous message passing
• actors = “green processes”
• efficient VM (SMP enabled since R12B)
• high reliability
© ericsson 2007
Thursday 21 October 2010
Erlang
spawn(fun() ->sort(Self, List) end)
pmap_gather([]) -> [];pmap_gather([H|T]) -> receive {H, Ret} -> [Ret|pmap_gather(T)] end;
Thursday 21 October 2010
Rubinius: Actors
• actors in the language: threads with inbox
• VM actors to communicate between actors in different VMs
Thursday 21 October 2010
Ruby: Revactor
• erlang-like semantics: actor spawn/receive, filter
• Fibers (so cooperative scheduling)
• Revactor::TCP for non-blocking network access (1.9.2) (rev eventloop)
Thursday 21 October 2010
Go
• Fairly low-level - fit for systems programming (close to C)
• static typing
• goroutines: parallel execution - sort of async lightweight thread
• channels !
Thursday 21 October 2010
GolessReply = make(chan []int)
(...)lessReq.data = less
lessReq.replyChannel = lessReplygo sort(&lessReq) // asyncstart parallel execution of sort
listener:
append(<-lessReply, pivot, <-greaterReply)
Thursday 21 October 2010
clojure
functional, Lisp-like
concurrency: Software Transactional Memory System:
• Vars = variable state is thread isolated
• Refs = shared, and mutation within a transaction (atomic, consistent, isolated) - Multiversion Concurrency Control -
Thursday 21 October 2010
Ruby: STM
• @mentalguy thought experiment
• @technomancy clojure-gem
Thursday 21 October 2010
others to handle concurrency
futures
joins
see http://moonbase.rydia.net/mental/blog/programming/concurrency-five-ways.html (@mentalguy)
Thursday 21 October 2010
Kernel stuff
Some of these problems have been solved before ...
Thursday 21 October 2010
FUN :)
Thursday 21 October 2010
References:
http://www.delicious.com/elisehuard/concurrency
http://github.com/elisehuard/rubyandrails-2010
Elise Huard
@elise_huard
http://jabberwocky.eu
Thursday 21 October 2010