JOjosephg·Jul 14, 2022
About a decade ago I hand-ported the chipmunk2d physics engine to javascript. After porting it, I tried about 30 different things trying to make the code run faster. Some things I tried made it faster. Some made it slower.
The most performance-critical section is the "arbiter applyImpulse" physics code[2], which is all math.
I tried putting everything in as big TypedArray to avoid all the object lookups, but performance got slightly worse, not better. I still have no idea why. I think the reason is that the optimizer couldn't optimize the typedarray lookups at the time. Not in the same way it can optimize math on normal objects.
Maybe v8 is more clever now? I dunno!
The biggest performance win I got was from inlining vector fields. Chipmunk heavily uses {x,y} 2d vectors. Lots of objects looked like this: {pos: {x, y}, velocity: {x, y}, ..
Read the rest
.}. Flattening everything to this {posx, posy, velocityx, velocityy, ...} made the code uglier. But it caused a massive performance improvement because it reduced the number of objects allocated on the heap. (This one change reduced the number of heap allocations by about 70% from memory, and it caused a double-digit performance improvement overall.)
As I see it, Javascript will always be much slower than other languages for complex data structures because everything is stored on the heap.
[1] https://github.com/josephg/chipmunk-js
[2] https://github.com/josephg/Chipmunk-js/blob/ec447072458f4009...