Sweating the Small StuffOptimization and tooling

FCNY July 2010

Machinarium

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

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.)

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

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

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

• ?

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

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…?

Wireworld in a nutshell

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

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.

}}

Naïve implementation

Result: sucks Slow, slow, slow, slow. Touching every pixel seems dumb

Naïve

Performance

New idea

List the pixels (or nodes) that might change their neighbors

for ( each node in the list) {

for ( each neighbor of the node) {

if ( the neighbor might 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

Linked List instead of Array Arrays

untyped (slow) ordered (unnecessary) weird push() and pop() are expensive and

lame

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: betterNaïve Linked Lists

Performance

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:

1 Addressing bad user experience, freezing process2 Facing stiff competition3 Porting code to mobile devices

4 p l o t t i n g w o r l d d o m i n a t i o n Otherwise, don’t we all have enough

on our plates already?

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: disappointingNaïve Linked Lists Convolution Pixel Bender

Performance

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 with ints, Booleans and other Vectors

The Vectors don't grow or shrink, but the data changes its value Nodes now point to each other with an

index The linked lists are still in there

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.

Naïve Linked ListsProperty Vectors

Performance

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!Naïve Linked ListsProperty Vectors ByteArray

Performance

Wait. What??

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

Finally, the TDSI step

Use TDSI’s Memory API Slows your program way down at first

(Don’t freak out)

Run the SWF through TDSI

Result: Excellent

Naïve Linked Lists

Property Vectors

ByteArray TDSI ByteArray

Performance

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 Framerate threshold

Don’t forget to solve the problem

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

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)

Fitting tools like TDSI into your workflow

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

BATBASH

That’s it. Please direct all your questions to

Hudson. Thank you.