Re: Garbage collection

[James McCartney <asynth@...>]

On Friday, November 1, 2002, at 12:32  PM, Steve Dekorte wrote:

> On Friday, November 1, 2002, at 12:21 PM, James McCartney wrote:
> > On Thursday, October 31, 2002, at 03:59  PM, Steve Dekorte wrote:
> > > so only the freed objects are touched on a sweep.
> >
> > Just to press the point, with Baker's treadmill you don't even have 
> > to do that.
>
> I just made a small change to make the definitions of black and white 
> dynamic that avoids it. Maybe this is equivalent to "Baker's 
> treadmill"? The descriptions I've read of it weren't very clear to me.

With the treadmill you've got linked lists of grey, black, white and 
free. To scan an object you remove it from the grey list to black and 
put all of the objects it points to onto the grey list. Once the grey 
list is exhausted then everything on the white list is not live and so 
the entire white list can be linked onto the free list. This requires 
changing 6 list pointers. Then you change the meaning of the color bits 
so that black now means white and start over.

With a treadmill, since there is no sweep then there is not a built in 
way to do finalization. There are ways to get around it, such as using 
a separate treadmill for finalizable objects and sweeping that one. I 
used that for a while, but decided to it would be better for real time 
performance to avoid finalization altogether. Instead I put things that 
need to be finalized onto a known live list (e.g. 'allOpenFiles') to 
keep them live until I manually close them.

--
--- james mccartney   james@audiosynth.com   <http://www.audiosynth.com>
SuperCollider - a real time synthesis programming language for the 
PowerMac.
<ftp://www.audiosynth.com/pub/updates/SC2.2.16.sea.hqx>