Thursday, April 23, 2009

sequential render

Last semester, I wrote up the semantics of a kernel of CSS and proposed a parallel evaluation strategy, but never got to implementing it beyond seeing how a very simple computational model of it would perform. It wasn't clear that the semantics made any sense... until now.

Running it sequentially:

Line-wrapping horizontal layout, including a vertical layout child, an image (white box, blogger killed it), and some text.

Thus, my parallel vertical and horizontal layout decompositions make sense. I'll try to parallelize these over the next week couple of weeks for the proof-of-concept before moving on to floats (viz. speculative execution) and then figuring out table semantics. The biggest stumbling block is actually calling into lower-level systems, not the algorithm itself. I don't know them, and need to worry about things like reentrant calls into font libraries when I'm sure they're doing optimizations requiring synchronization like memoization. On the plus side, I can finally learn some of Knuth's formatting algorithms (and modernize them ;-)).

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