High level concurrency

High%level)Concurrency

"Robert"Brown"August"2015"@robby_brown

https://twitter.com/robby_brown

Overview

1. The&Problems

2. Architecture&Theory

3. Examples

4. Demo



The$Problems



Atomicity



Nondeterminism



Race%Condi+ons



Mutual&Exclusion



Dead%lock



The$list$goes$on...



Keeping'track'of'so'much'informa3on'is'hard



Computers*are*good*at*tracking*lots*of*informa4on



We#write#code#that#tests#code.

We#write#code#that#generates#code.



Let's&use&a&system&that&lets&the&computer&manage&concurrency



Architecture)Theory



Actor&Model



A"universal"primi.ve"of"concurrent"computa.on."Defini(on"of"an"Actor1

1"Wikipedia


https://en.wikipedia.org/wiki/Actor_modelhttps://twitter.com/robby_brown

[T]he&problem&with&[OOP]&languages&is&theyve&got&all&this&implicit&

environment&that&they&carry&around&with&them."Joe"Armstrong3

3"Coder's"at"Work


http://www.amazon.com/gp/product/1430219483https://twitter.com/robby_brown

You$wanted$a$banana$but$what$you$got$was$a$gorilla$holding$the$banana$

and$the$en3re$jungle."Joe"Armstrong3

3"Coder's"at"Work


http://www.amazon.com/gp/product/1430219483https://twitter.com/robby_brown

I'm$sorry$that$I$long$ago$coined$theterm$"objects"$for$this$topic$because$it$gets$many$people$to$focus$on$the

lesser$idea."Alan"Kay2

2"Squeak"Mailing"List


http://lists.squeakfoundation.org/pipermail/squeak-dev/1998-October/017019.htmlhttps://twitter.com/robby_brown

The$key$in$making$great$and$growable$systems$is$much$more$to$

design$how$its$modules$communicate$rather$than$what$their$internal$proper7es$and$behaviors$

should$be."Alan"Kay2

2"Squeak"Mailing"List


http://lists.squeakfoundation.org/pipermail/squeak-dev/1998-October/017019.htmlhttps://twitter.com/robby_brown

Protocol'oriented,programming,focuses,on,interac4ons,rather,than,

object,hierarchies.See#WWDC#2015#Session#408


https://developer.apple.com/videos/wwdc/2015/?id=408https://twitter.com/robby_brown

Actor&Opera+ons4

1. Make'local'decisions

2. Create'other'actors

3. Send/receive'messages

4"Wikipedia


https://en.wikipedia.org/wiki/Actor_modelhttps://twitter.com/robby_brown

Warning:(Flow(Charts(Ahead5

5"XKCD"518


https://xkcd.com/518/https://twitter.com/robby_brown

Typical(Actor(Flow



ExampleYour%Code%as%a%Crime%Scene


https://pragprog.com/book/atcrime/your-code-as-a-crime-scenehttps://twitter.com/robby_brown

Sequen&al)Processing



Concurrent)Processing



Parallel&Processing



Monad&Binding



Two$level(Aggrega-on



Interchangable,Parts



Other&Examples



Instagram



Deckset



LLVM6

6"LLVM"for"Grad"Students


http://adriansampson.net/blog/llvm.htmlhttps://twitter.com/robby_brown

Automator



IFTTT



Workflow



Summary

1. The&Problems

2. Architecture&Theory

3. Examples

4. Demo



One$Final$Thought



The$Main$Thread$is$a$Singleton!

!!"!#!$!%



Demo



Ques%ons?



Resources(to(Learn(More WWDC%2015%Session%226

Actor%Model

Communica;ng%Sequen;al%Processes%(CSP)


https://developer.apple.com/videos/wwdc/2015/?id=226https://en.wikipedia.org/wiki/Actor_modelhttps://en.wikipedia.org/wiki/Communicating_sequential_processeshttps://twitter.com/robby_brown

In#Depth#Resources MapReduce

Lambda-Architecture

Reac3ve-Streams

WWDC-2015-Session-408

Amdahl's-Law


https://en.wikipedia.org/wiki/MapReducehttps://en.wikipedia.org/wiki/Lambda_architecturehttp://www.reactive-streams.orghttps://developer.apple.com/videos/wwdc/2015/?id=408https://en.wikipedia.org/wiki/Amdahl%27s_lawhttps://twitter.com/robby_brown

High level concurrency

Software

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