Artisan Coder » garbage collector http://www.artisancoder.com Software development as a craft Thu, 15 Dec 2011 10:57:08 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Adding a garbage collector http://www.artisancoder.com/2009/05/adding-a-garbage-collector/ http://www.artisancoder.com/2009/05/adding-a-garbage-collector/#comments Tue, 05 May 2009 15:00:12 +0000 Alex http://www.ventonegro.org/?p=96 I guess it is clear by now that I am writing a toy Scheme compiler and virtual machine. Primarily for learning the techniques, I just touch it from time to time. The last addition to the virtual machine was a Cheney-style copy garbage collector. I wanted to implement a very simple algorithm to get a functioning system quicker. The simplest algorithms I know of are the Cheney one and the Deutsch-Schorr-Waite mark-and-sweep garbage collector. I chose the copying one because I believe generational garbage collection is the way to go for Scheme virtual machines, given that the rate of allocation is very high (allocation in a copy garbage collector is just moving a pointer) and most data objects die young (how many times did you use reverse after a loop?).

I was surprised by how easy it was to implement the collector. It is a very simple one (stop-the-world, two semi-spaces etc.) but nevertheless I always thought garbage collectors were somewhat magical, a bunch of elves that worked out of sight to keep your process working perfectly. This is exactly why I am writing such a system, even if it never gets free onto the world it will fulfill its purpose. Of course, if I am satisfied with the result, I will release the beast.

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