Titanium - Making the most of your single thread
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The document emphasizes the importance of optimizing single-threaded applications to enhance user experience by avoiding UI blocking and managing event responsiveness. It discusses issues like the lack of loading indicators and strategies such as using _.defer and _.throttle to ensure that user actions are handled efficiently without overwhelming the single thread. Recommendations include implementing visual feedback for users and controlling function execution rates to prevent performance degradation.
![Call Stack
[click]
foo()
‘events’
0
0
0
6
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
nerf()
bar()
foo()
0
ms
10
bar()
bar()
bar()
bar()
30
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click
handler
20
ms](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-19-320.jpg)
![Call Stack
ms
In Titanium the queue is
FIFO (first in, first out).
[click]
foo()
0
0
0
6
10
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
nerf()
bar()
foo()
0
‘events’
10
bar()
bar()
bar()
bar()
40
50
click
bar()
handler
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ms
30](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-20-320.jpg)
![Call Stack
[click]
foo()
‘events’
0
0
0
6
10
20
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
Interval & Timer fire
nerf()
bar()
foo()
0
ms
10
bar()
bar()
bar()
bar()
click
bar() nerf()
handler
20
ms
30
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50](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-21-320.jpg)
![Call Stack
ms
The interval at 20ms is
ignored, an execution is
already scheduled.
[click]
foo()
0
0
0
6
10
20
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
Interval & Timer fire
nerf()
bar()
foo()
0
‘events’
10
bar()
bar()
bar()
bar()
click
bar() nerf()
handler
20
ms
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50](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-22-320.jpg)
![Call Stack
ms
The interval at 30ms is
queued, since no
execution is scheduled.
[click]
foo()
0
0
0
6
10
20
30
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
Interval & Timer fire
Interval fires
nerf()
bar()
foo()
0
‘events’
10
bar()
bar()
bar()
bar()
click
bar() nerf() bar()
handler
20
ms
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50](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-23-320.jpg)
![Call Stack
ms
‘events’
nerf()
0
0
0
6
10
20
30
40
foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
Interval & Timer fire
Interval fires
Interval fires
bar()
bar()
Interval at 40ms is
ignored.
[click]
foo()
bar()
foo()
0
10
bar()
bar()
click
bar() nerf() bar()
handler
20
ms
30
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50](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-24-320.jpg)
![Call Stack
ms
Interval at 50ms is the first
to execute at the correct
time (though 2 executions
were dropped).
[click]
foo()
nerf()
bar()
foo()
0
10
bar()
‘events’
0
0
0
6
10
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30
40
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foo()
setInterval(bar, 10)
setTimeout(nerf, 20)
Button clicked
Interval fires
Interval & Timer fire
Interval fires
Interval fires
Interval fires
bar()
bar()
click
bar() nerf() bar()
handler
20
ms
30
40
bar()
bar()
50](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-25-320.jpg)
![Underscore - Defer
_.defer(function, [*arguments])
Defers invoking the function until the current call stack has cleared,
similar to using setTimeout with a delay of 0. Useful for performing
expensive computations or HTML rendering in chunks without blocking
the UI thread from updating. If you pass the optional arguments, they
will be forwarded on to the function when it is invoked.
!
_.defer ( function() { alert(‘deferred’); });
!
// Returns from the function before the alert runs.](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-28-320.jpg)
![Underscore - Throttle
_.throttle(function, wait, [options])
Creates and returns a new, throttled version of the
passed function, that, when invoked repeatedly,
will only actually call the original function at most
once per every wait milliseconds. Useful for ratelimiting events that occur faster than you can keep
up with.
var throttled = _.throttle ( updatePosition, 100);
$(window).scroll(throttled);](https://image.slidesharecdn.com/titanium-makingthemostofyoursinglethread-140110110425-phpapp02/85/Titanium-Making-the-most-of-your-single-thread-32-320.jpg)
Titanium - Making the most of your single thread
- 1. Making the most of your single thread Titanium - Fundamentals
- 2. Congrats! ! Your app is in the hands of the public! Your users click on buttons, open windows, and at some point someone touches a button that results in…
- 3. Absolutely Nothing. He tries touching it three times, before deciding, after a mere few seconds, that your app has crashed. ! He kills your app.
- 4. Had he waited for ‘but’ 5 seconds.. .. he would have noticed three windows opening in rapid succession. Three identical windows, as he would observe when using the ‘back’-button.
- 5. What did you do wrong? • There’s no loading indicator showing • There is no mechanic in place to prevent additional windows from opening
- 6. What did you do wrong? • There’s no loading indicator showing • There is no mechanic in place to prevent additional windows from opening • But more important: You blocked the UI far too long! You did not make the best use of your single thread!
- 7. Ronald Treur Co-founder Snowciety ! Freelance developer ! 2.5 yrs Titanium experience ! @ronaldtreur [email protected]
- 8. Making the Most of Your Single Thread • Threads & Threading • How it works in Native & Titanium • Javascript call stack example • Underscore - Defer
- 9. Thread The smallest subset of a process that could be independently handled by the OS. or The smallest piece of code, that could be executed independently from the rest of the code.
- 11. Threading • Multi-threaded: - Threads (can) run in parallel, meaning: - Multiple pieces of code can execute at the same time. #1 #2 ! #3 #4 ! • #1 Single-threaded: - Threads can only run serially, meaning: - Only one piece of code can execute at a time. #2 #3
- 14. How your app works JS Thread #1
- 15. Thread Safe Javascript is by definition NOT thread safe. • If multiple threads would be able to access and change the same object/variable, a race condition might occur. • aka: the outcome of a piece of code would be unpredictable.
- 16. Single Threaded Javascript is by definition NOT thread safe. Thus it is, by nature, single threaded. • Timers are not part of Javascript, they are part of the JS engine (Rhino, V8, JavaScriptCore) • Timers allow for asynchronous delays, but code execution remains single threaded. • When a timer expires, or an event fires, the resulting execution is queued.
- 18. Call Stack ms ‘events’ 0 0 0 foo() setInterval(bar, 10) setTimeout(nerf, 20) nerf() foo() bar() bar() bar() bar() bar() 30 40 50 foo() 0 10 20 ms
- 19. Call Stack [click] foo() ‘events’ 0 0 0 6 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked nerf() bar() foo() 0 ms 10 bar() bar() bar() bar() 30 40 50 click handler 20 ms
- 20. Call Stack ms In Titanium the queue is FIFO (first in, first out). [click] foo() 0 0 0 6 10 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires nerf() bar() foo() 0 ‘events’ 10 bar() bar() bar() bar() 40 50 click bar() handler 20 ms 30
- 21. Call Stack [click] foo() ‘events’ 0 0 0 6 10 20 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires Interval & Timer fire nerf() bar() foo() 0 ms 10 bar() bar() bar() bar() click bar() nerf() handler 20 ms 30 40 50
- 22. Call Stack ms The interval at 20ms is ignored, an execution is already scheduled. [click] foo() 0 0 0 6 10 20 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires Interval & Timer fire nerf() bar() foo() 0 ‘events’ 10 bar() bar() bar() bar() click bar() nerf() handler 20 ms 30 40 50
- 23. Call Stack ms The interval at 30ms is queued, since no execution is scheduled. [click] foo() 0 0 0 6 10 20 30 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires Interval & Timer fire Interval fires nerf() bar() foo() 0 ‘events’ 10 bar() bar() bar() bar() click bar() nerf() bar() handler 20 ms 30 40 50
- 24. Call Stack ms ‘events’ nerf() 0 0 0 6 10 20 30 40 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires Interval & Timer fire Interval fires Interval fires bar() bar() Interval at 40ms is ignored. [click] foo() bar() foo() 0 10 bar() bar() click bar() nerf() bar() handler 20 ms 30 40 50
- 25. Call Stack ms Interval at 50ms is the first to execute at the correct time (though 2 executions were dropped). [click] foo() nerf() bar() foo() 0 10 bar() ‘events’ 0 0 0 6 10 20 30 40 50 foo() setInterval(bar, 10) setTimeout(nerf, 20) Button clicked Interval fires Interval & Timer fire Interval fires Interval fires Interval fires bar() bar() click bar() nerf() bar() handler 20 ms 30 40 bar() bar() 50
- 26. Conclusions • If code is already executing, events and timers are queued • Timers may not execute exactly when you were expecting • Intervals may not fire as often as you were expecting • User interaction is queued as well, which the user interprets as the UI being unresponsive.
- 27. setTimeout vs setInterval setTimeout ( function nerf() { ….. setTimeout ( nerf, 10); }, 10); -VSsetInterval ( function() { ….. }, 10);
- 28. Underscore - Defer _.defer(function, [*arguments]) Defers invoking the function until the current call stack has cleared, similar to using setTimeout with a delay of 0. Useful for performing expensive computations or HTML rendering in chunks without blocking the UI thread from updating. If you pass the optional arguments, they will be forwarded on to the function when it is invoked. ! _.defer ( function() { alert(‘deferred’); }); ! // Returns from the function before the alert runs.
- 30. https://github.com/RonaldTreur/lp.DeferTests The above link contains the live demo test cases
- 31. Conclusions • Try to keep the User experience as responsive as possible. Use _.defer! • Always show loading-indicators when you can’t. • Limit the amount of actions everywhere in your app. For example: Widgitize your button and/or use _.throttle.
- 32. Underscore - Throttle _.throttle(function, wait, [options]) Creates and returns a new, throttled version of the passed function, that, when invoked repeatedly, will only actually call the original function at most once per every wait milliseconds. Useful for ratelimiting events that occur faster than you can keep up with. var throttled = _.throttle ( updatePosition, 100); $(window).scroll(throttled);