Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
360|iDev Concurrency Workshop
Search
sammyd
August 21, 2016
Programming
1
310
360|iDev Concurrency Workshop
Slides accompanying the 360|iDev concurrency workshop from 2016
sammyd
August 21, 2016
Tweet
Share
More Decks by sammyd
See All by sammyd
Core Image: Great when it works
sammyd
1
500
iOS Views & Animations: Learning by stealing
sammyd
1
170
Machine Learning on Mobile—a primer
sammyd
0
98
Core ML: A whistlestop tour
sammyd
1
150
DIY DI
sammyd
2
110
iOSConfSG 2017: Decoding Codable
sammyd
3
190
Machine Learning: deciphering the hype
sammyd
0
130
Notify Me, Notify You. Aha!
sammyd
1
170
SwiftConf 2016: Concurrency on iOS
sammyd
1
170
Other Decks in Programming
See All in Programming
レトロゲームから学ぶ通信技術の歴史
kimkim0106
0
110
Python型ヒント完全ガイド 初心者でも分かる、現代的で実践的な使い方
mickey_kubo
1
240
初学者でも今すぐできる、Claude Codeの生産性を10倍上げるTips
s4yuba
16
13k
20250704_教育事業におけるアジャイルなデータ基盤構築
hanon52_
5
1.1k
PHPでWebSocketサーバーを実装しよう2025
kubotak
0
320
テスト駆動Kaggle
isax1015
1
620
PicoRuby on Rails
makicamel
2
140
20250708_JAWS_opscdk
takuyay0ne
2
130
可変変数との向き合い方 $$変数名が踊り出す$$ / php conference Variable variables
gunji
0
180
#QiitaBash MCPのセキュリティ
ryosukedtomita
1
1.5k
AI Agent 時代のソフトウェア開発を支える AWS Cloud Development Kit (CDK)
konokenj
6
800
RailsGirls IZUMO スポンサーLT
16bitidol
0
200
Featured
See All Featured
Making Projects Easy
brettharned
116
6.3k
[RailsConf 2023 Opening Keynote] The Magic of Rails
eileencodes
29
9.6k
Navigating Team Friction
lara
187
15k
Practical Orchestrator
shlominoach
189
11k
Designing Dashboards & Data Visualisations in Web Apps
destraynor
231
53k
Optimizing for Happiness
mojombo
379
70k
Building a Modern Day E-commerce SEO Strategy
aleyda
42
7.4k
Fashionably flexible responsive web design (full day workshop)
malarkey
407
66k
Docker and Python
trallard
45
3.5k
Done Done
chrislema
184
16k
The Myth of the Modular Monolith - Day 2 Keynote - Rails World 2024
eileencodes
26
2.9k
Faster Mobile Websites
deanohume
308
31k
Transcript
Concurrency workshop Sam Davies @iwantmyrealname _ github.com/sammyd git.io/v6waD
concurrency is hard
what is concurrency?
why use concurrency?
common concurrency problems
race condition
Race Condition time Value 1 Thread 1 Thread 2 inc
Race Condition time Value 1 1 Thread 1 Thread 2
inc r1
Race Condition time Value 1 1 1 Thread 1 Thread
2 inc r1 +1
Race Condition time Value 1 1 1 2 Thread 1
Thread 2 inc r1 w2 +1
Race Condition time Value 1 1 1 2 2 Thread
1 Thread 2 inc r1 w2 +1 inc
Race Condition time Value 1 1 1 2 2 2
Thread 1 Thread 2 inc r1 w2 +1 inc r2
Race Condition time Value 1 1 1 2 2 2
2 Thread 1 Thread 2 inc r1 w2 +1 inc r2 +1
Race Condition time Value 1 1 1 2 2 2
2 3 Thread 1 Thread 2 inc r1 w2 +1 inc r2 w3 +1
Race Condition time Value 1 Thread 1 Thread 2 inc
Race Condition time Value 1 1 Thread 1 Thread 2
inc r1 inc
Race Condition time Value 1 1 1 Thread 1 Thread
2 inc r1 inc r1
Race Condition time Value 1 1 1 1 Thread 1
Thread 2 inc r1 inc r1 +1
Race Condition time Value 1 1 1 2 1 Thread
1 Thread 2 inc r1 inc r1 w2 +1
Race Condition time Value 1 1 1 2 1 2
Thread 1 Thread 2 inc r1 +1 inc r1 w2 +1
Race Condition time Value 1 1 1 2 1 2
2 Thread 1 Thread 2 inc r1 w2 +1 inc r1 w2 +1
priority inversion
Priority Inversion time low priority resource
Priority Inversion time low priority resource
Priority Inversion time low medium priority resource
Priority Inversion time low medium high priority resource
Priority Inversion time low medium high priority resource
Priority Inversion time low medium high priority resource
Priority Inversion time low medium high priority resource
deadlock
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
Deadlock time resource1 resource2 Thread 1 Thread 2
$&'( queueueueueue paradigm
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
Tasks & Queues Thread 1 Thread 2 Queue
feeling brave?
a touch more theory
Thread Safety time Value 1111 Thread 1 Thread 2 Thread
3
Thread Safety time Value 1111 Thread 1 Thread 2 r1111
Thread 3
Thread Safety time Value 1111 1112 Thread 1 Thread 2
r1111 w2222 Thread 3
Thread Safety time Value 1111 1112 1122 Thread 1 Thread
2 r1111 w2222 r1122 Thread 3
Thread Safety time Value 1111 1112 1122 1223 Thread 1
Thread 2 r1111 w2222 r1122 w3333 Thread 3 r1223
Thread Safety time Value 1111 1112 1122 1223 2233 Thread
1 Thread 2 r1111 w2222 r1122 w3333 Thread 3 r1223
Thread Safety time Value 1111 1112 1122 1223 2233 2333
Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223
Thread Safety time Value 1111 1112 1122 1223 2233 2333
3333 Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223
Thread Safety time Value 1111 1112 1122 1223 2233 2333
3333 3333 3333 Thread 1 Thread 2 r1111 w2222 r1122 r2333 w3333 Thread 3 r1223 r3333 r3333
Dispatch Barrier time task task task task task barrier task
task task task task task task task
Dispatch Barrier time read read read read read read write
read read read read read read
alternatives to
promises networkRequest(url, callback: { data in decompressor(data, callback: { image
in imageResizer(image, callback: { small in filterImage(small, callback: { filtered in displayImage(filtered) }) }) }) })
promises promise<int> int error
promises str
promises promise<img> str f
promises promise<img> str error f img
promises promise<img> str error f img error handler
promises promise<img> str error f img g promise<img> error handler
promises promise<img> str error f img g promise<img> error error
handler img
promises promise<img> str error f img g promise<img> error error
handler img
promises networkRequest(url) .then(decompressor) .then(imageResizer) .then({ (image) in return filterImage(image) }).then(displayImage)
.catch({ (error) in print(error) })
imagine the “promise pipeline” accepted a sequence of values…
that’s reactive programming
conclusion
concurrency is hard
you will get it wrong
• raywenderlich.com/videos • git.io/v6waD • @iwantmyrealname