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
510
iOS Views & Animations: Learning by stealing
sammyd
1
170
Machine Learning on Mobile—a primer
sammyd
0
110
Core ML: A whistlestop tour
sammyd
1
160
DIY DI
sammyd
2
110
iOSConfSG 2017: Decoding Codable
sammyd
3
200
Machine Learning: deciphering the hype
sammyd
0
140
Notify Me, Notify You. Aha!
sammyd
1
170
SwiftConf 2016: Concurrency on iOS
sammyd
1
170
Other Decks in Programming
See All in Programming
コードとあなたと私の距離 / The Distance Between Code, You, and I
hiro_y
0
160
私達はmodernize packageに夢を見るか feat. go/analysis, go/ast / Go Conference 2025
kaorumuta
2
560
株式会社 Sun terras カンパニーデック
sunterras
0
310
Django Ninja による API 開発効率化とリプレースの実践
kashewnuts
0
1.3k
Le côté obscur des IA génératives
pascallemerrer
0
150
あなたとKaigi on Rails / Kaigi on Rails + You
shimoju
0
160
All About Angular's New Signal Forms
manfredsteyer
PRO
0
160
CSC509 Lecture 05
javiergs
PRO
0
300
詳しくない分野でのVibe Codingで困ったことと学び/vibe-coding-in-unfamiliar-area
shibayu36
3
5k
Software Architecture
hschwentner
6
2.3k
Advance Your Career with Open Source
ivargrimstad
0
530
CSC509 Lecture 04
javiergs
PRO
0
300
Featured
See All Featured
Unsuck your backbone
ammeep
671
58k
Building Applications with DynamoDB
mza
96
6.7k
Rebuilding a faster, lazier Slack
samanthasiow
84
9.2k
How STYLIGHT went responsive
nonsquared
100
5.8k
Designing Dashboards & Data Visualisations in Web Apps
destraynor
231
53k
Making Projects Easy
brettharned
120
6.4k
Into the Great Unknown - MozCon
thekraken
40
2.1k
VelocityConf: Rendering Performance Case Studies
addyosmani
332
24k
Faster Mobile Websites
deanohume
310
31k
Dealing with People You Can't Stand - Big Design 2015
cassininazir
367
27k
[RailsConf 2023 Opening Keynote] The Magic of Rails
eileencodes
31
9.7k
Java REST API Framework Comparison - PWX 2021
mraible
34
8.9k
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