Re: Fusion-ifying proto parse trees

Eric Niebler wrote:
> Joel de Guzman wrote:
> > Eric Niebler wrote:
> > > Time taken to construct the ET and traverse it was measured. The 
> > > winner by a wide margin is (3) segmented proto.
> >
> > Great! It would be nice if the 1) time taken to construct the ET
> > and 2) the time to traverse it, are reported separately. For spirit,
> > while 1 is important, 2 is more important by a wide margin. It's
> > a balance, I can tolerate a few clock cycles for 1 if that would
> > improve 2. So, it's very important to see both timings.
>
>
> What is it about Spirit's usage scenario that makes traversal time more 
> important than ET construction time? I ask because it could affect the 
> design. My understanding is that you wanted the first-phase proto ET to 
> be immediately executable because people declare rules inline in calls 
> to spirit::parse, where they are immediately executed without the 
> opportunity for a 2nd ET phase. In this scenario, it seems to me the 
> only thing that matters is end-to-end time: ET construction + traversal. 
> Or have I been working with the wrong usage scenario in mind?

You spend more time traversing the nodes than in the one-time-only
construction. That's why. Consider a trivial parser:

    parse(f,l, int_ >> *(',' >> int_));

You construct the parser only once, but you traverse the parser nodes
N times. And N can be significant in a lot of cases. Megabytes of
stuff to parse is not unimaginable.

> > It would also be nice to see the App footprint, but I guess it's
> > too early to do that now.
>
> What is "App footprint"? Code size? Memory usage?

Code size, I think. But forget that for now.

Cheers,
--
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net



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