> I've read the advice in the Programmatic Programmers Guide, removed all
> my obvious newbie errors, but it's still too slow.
> 
> The profiler identifies all the major bottlenecks as low level ruby
> methods (.each etc), so I'm considering re-implemented the guts of the
> dependency analysis in C++. I'm sure people here have done similar things,
> so I was wondering how beneficial it was for them?

Each shows high in a profiler, because the entire contents of the inner
part of the loop count against it. Just so you're warned.

Ari