Sweating the Small Stuff

1. Sweating the Small Stuff Optimization and tooling FCNY July 2010

2. Machinarium

3. Here's what this talk is about • AS3 is only a tool • Apparat and TDSI • Wireworld code remap example • Adding your Tools to a Build Process • Q & A • Kumbaya

4. AS3 ≠ Flash • Many languages can script SWFs • AS3, MXML, AS2,HaXe, C, C++, Lua… • Different reasons to use each one • AS3: common • Alchemized C: runs fast, but hard to write • HaXe: runs fast, targets practically everything • (Tramp.)

5. AS3 ≠ Flash • Did you know? • Alchemy C code can run at 30% the speed of native C code • AS3? 3% • Use the tools at your disposal • Pick the right tools for the right job • You can use more than one at a time, you know

6. Apparat • Behind Audiotool • Joa Ebert • TAAS – bytecode analyzer, optimizer • Stripper – removes SWF debug data • Reducer – compresses PNGs in SWFs • Concrete – lets you implement abstract classes • Coverage – unit testing thingy • TDSI

7. TDSI • It's a car modding term. • We're not supposed to get it. • Finds slow "dummy code" in your SWF that you deliberately placed in your AS3 • Replaces them with Alchemy opcodes • Fast Math replacement • Memory system • Inlining and macros • ?

8. So here’s what we’re going to do We’ll start with a slow AS3 app and improve it in stages. Generally applicable strategies for optimization

9. Wireworld in a nutshell • Particle system… but stuck in a grid • Information leaks from pixel to pixel • Instead of • particle.move(); particle.drop(); • It’s • pixel.countNeighbors(); pixel.changeColor(); • Supports circuit-like systems • WW computer by Owen and Moore (Quinapalus.com) • wireworldAS3 (Google Projects) • I get a lot of attention from Germans…?

10. Wireworld in a nutshell

11. DISCLAIMER • wireworldAS3 is needlessly complicated. • Show and tell • This complexity isn’t required from your own projects. • the Apparat project contains some example code that may be easier to follow at home

12. Naïve implementation for ( every row ) { for ( every column ) { there is a pixel. for ( every neighbor of the pixel ) { do something. } update the pixel's state. } }

13. Naïve implementation • Result: sucks • Slow, slow, slow, slow. • Touching every pixel seems dumb

14. New idea • List the pixels (or nodes) that might change theirneighbors for ( each node in the list) { for ( each neighbor of the node) { if ( the neighbormight change its neighbors next time ){ add it to a new list } update the node } } Then swap the old list with the new list. • Way less work

15. Linked List instead of Array • Arrays • untyped(slow) • ordered (unnecessary) • weird • push() and pop() are expensive and lame

16. Linked List instead of Array • Linked lists are easy: every node points to the next node in the list • start  node  node  node  node  null • Chop it and you get two LLs • Connect their ends and they’re one again • No pushing or popping • No class • Result: better

17. Let’s take a breather • Grab that second beer. • Optimization is never an end unto itself • It’s so easy to forget that • Performance matters in four or five situations: • Addressing bad user experience, freezing process • Facing stiff competition • Porting code to mobile devices • plotting world domination • Otherwise, don’t we all have enough on our plates already?

18. Are there any other bright ideas? • How about filters? Pixel Bender? • Wireworld rule is basically a weird BitmapFilter • These work, but they're slow • Remapping to these is scary • Some tasks can be PBJ'd, but not all of them • Result: disappointing

19. Property Vectors instead of objects • Make a Vector for each node property • xVec, yVec, stateVec • node.next.x becomes xVec[ nextVec[ i ] ] • Replaces the node class withints, Booleans and other Vectors • The Vectors don't grow or shrink, but the data changes its value • Nodes now point to each other with anindex • The linked lists are still in there

20. Property Vectors instead of objects • Wait! We can't use null. • You have to make a custom null. Call it something else. Nada. Diddly. Buggerall. Squat. Bupkis. • It’s just an int, like -1, that we use to signify nothingness. • Doesn’t work well with dynamic properties • There are ways around this • Maybe you shouldn’t be using dynamic properties • Result: on par with linked lists • Main advantage: all the data is primitive.

21. ByteArray time • We can pack our primitive data into a BA • Write out the values of each property for each cell, same order every time. • Result: • SUCKS!

22. Wait. What??

23. Wait. What?? • BAs + [your project] = SUPAH FAST!!!1 • Dopes.BAs aren’t a cure-all. • ByteArray.position • Like a needle on a record player or hard disk • It’s fast, as long as you don’t lift that needle • BAs in AS3 will perform well for you in many cases, just not all cases • TDSI manipulates BAs with Alchemy opcodes, not the BA methods

24. Finally, the TDSI step • Use TDSI’sMemory API • Slows your program way down at first • (Don’t freak out) • Run the SWF through TDSI • Result: Excellent

25. Bonus: green threads • Cut a big loop into a repeatable task • Perform the task in response to a timed event • Stop the task when the loop test fails • Overdrive • Packing the flash event loop • Frameratethreshold • Don’t forget to solve the problem

26. Was all that really worth it? • Wireworld won’t impact most people. • Other systems can seriously benefit • Audio players/synths • Emulators • Graphics engines • Solvers • Tough stough

27. Was all that really worth it? • Consider: • This is probably the most efficient SWF we've ever compiled during a talk at FCNY • Hard task • Runs fast • Targeting mobile devices • Your app will stand a better chance • (Apparently WW already runs nice on Froyo)

28. Fittingtools like TDSIinto your workflow BASH BAT • Bash script / Bat file • Write it just once • Tack it on the end of your FB builders list • Register it as an external build tool • Most IDEs offer some way of doing this • Double click it • Ant build for Eclipse fans • AGAIN: implementation before optimization

29. That’s it. Please direct all your questions to Hudson. Thank you.