Comment by Raphael_Amiard | Hacker News Reader

Comment by Raphael_Amiard | Hacker News Reader

This is great news ! I don't know if Mike Pall reads Hacker News, but a couple ideas come to my mind :

- May it be a good idea to create a KickStarter page ? I know LuaJit has its own donation mecanism, but it may help it gain further exposure. I know i'd be willing to donate for a better GC in either case.

- Mike mentions it has to be a non-moving collector, which is usually known for having worse performance than moving collectors. Also, a non-moving generational collector (and incremental, since this is also a requirement) is hard to get right.

I tried implementing a GC along the lines of this paper : http://www.pllab.riec.tohoku.ac.jp/papers/icfp2011UenoOhoriO... which presents a fast non moving collector. Incidentally it has ideas similar to those presented in this article. Maybe it could be a good source of inspiration ? I realize the ideas are maybe not as production grade since there is only one language implementation with a GC of this sort.

Yes, I thought about crowdfunding. But I fear that a) the Lua community is way too small to gather enough interest and b) it looks like the whole crowdfunding idea is rapidly deteriorating into an arms race of marketing experts. So many people are now jumping on that bandwagon. You'll never make it, unless you stay on the frontpages somehow.

Alas, I'm not good at marketing and a garbage collector is a very technical and very unsexy project (for most people, anyway). I should make up a silly name for it, that bears no relation to what it does. Yeah, that would do ...

Thank you for the link to the paper! I'll check it out.

I have good evidence that it's possible to create a non-moving GC that doesn't suck. It's a bit like marrying the best-of-breed of malloc implementations with the best-of-breed of incremental mark & sweep collectors. Plus some crazy ideas I'll have to experiment with first ...

The paper i linked outlines a GC that uses bitmap marking, which is i believe the same technique you use in arenas.

The main innovation consists basically of having separate heaps for different objects sizes. It starts with a size of i, and has heaps for sizes i^1, i^2, ..., i^n for bounded n. An object that has a size of m > i^n goes into the i^n+1 heap.

It does thus waste memory at the end of object blocks, but they seem to indicate this is on par with memory wasted by fragmentation (this of course needs to be proofed).

The very big advantage is basically costless deallocation and cheap maintenance of free lists (you just mark the block as unused). It does also trigger several optimizations idea regarding lost space at the end of objects.

I don't know if you'd consider it battle proofed enough though, but i really think it's an interresting idea ! And the benchmarks seem to indicate very good performance.

Anyway, congrats on the 4-colors algorithm, and thank you for this article, it is actually a quite thorough explanation of mark & sweep techniques, i enjoyed reading it !

Any ideas why you get more sponsorship from gaming companies? Seems like this would be really useful for mobile devices.

Also, has anyone tried to pre-jit then load an image on iOS?

Err, I think you mean "why DON'T you get ...". :-/

I guess this has to do with the way the gaming industry works. The smaller game companies have maybe two or three big hits until they go under and/or the talent is bought out. The bigger ones are just wrappers for financial purposes nowadays. Yes, there are a few exceptions (no point in listing them). But overall, there's little continuity.

Sponsoring is an investment into the future. Most game companies drown in their daily business and never get to look beyond that. Making the next deadline is all that counts. Après nous le déluge.

Ok, so maybe this is just my personal impression and I'm all wrong. In fact, I'd love to be corrected ...

Unfortunately, I think most mobile devices still forbid JIT (aside from integrated javascript implementations). The technical limitation was removed in iOS 5.0, but I believe whether Apple will accept apps using JIT is still an open question. Where I learned this: http://news.ycombinator.com/item?id=3818994

Right that's why you jit ahead of time and then load the result into executable memory when the app starts (vs while it's running)

I didn't know that was possible - thanks for the insight!

Permit me a shameless plug for my new crowdfunding site, BountyOSS: https://bountyoss.com/

It works quite differently from Kickstarter; I think it's more appropriate for Open Source software projects.

It's still a bit rough -- I even hesitate to mention it here on HN just yet -- but I think it's usable.

Kickstarter (last I checked) requires you to be American, so it won't fly for Mike (who is German).

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