[jhc] good news everyone

[Vinicius Callegari]

Hi people

I'm a little outdated regarding the current status of jhc. As John said he'd
wired in a garbage collector, does it mean that jhc doesn't use region
inference anymore?

I've set up a party today so I can impress the girls with that... (just
kidding :-)


2010/4/8 John Meacham <john at repetae.net>

> I have finally gotten around to what I have been promising to do for
> years and implemented a garbage collector for jhc. It is still fairly
> rough, but is very promising. In truth, I was worried it might kill
> jhc's performance advantage, but quite the opposite, it actually
> improves the performance of several benchmarks, and doesn't cut too deep
> into jhc's speed advantage in others.
>
>
> In particular, it seems to help ones where jhc did particularly worse
> than ghc, I had always assumed those cases were due to some pathological
> case in an inner loop that ghc was able to catch but jhc wasn't, but it
> turns out the presence of the GC played some role in their speed. I am
> not sure whether it is the short circuiting redirects or memory locality
> that is helping.
>
> In any case, JGC seems to be a couple times faster than the boehm
> collector so all in all, it is a good option to have. Right now, using
> jgc means you have to link against the judy library, this restriction
> may or may not be lifted in the future. libJudy is an amazingly useful
> and versatile library, keeping the GC information stored independently
> of the heap allows me to garbage collect without trouncing all over the
> memory space and I think this is key to getting acceptable performance
> from the GC.
>
> I am actually quite pleased with the results, the implementation is a
> very naive mark-and-don't-quite-sweep collector and achieves good
> performance, in particular, it isn't even generational. So there is
> still a fair amount of room for speed improvement.
>
> The GC is still experimental, it still doesn't support some features
> like IORefs and the method for collecting gc roots is fairly brute force
> and sloppy, but the essential work is done.
>
>        John
>
> --
> John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/
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