Re: [openvrml-develop] Re: Vrml97Parser Performance

[Braden M. <br...@en...>]

On Fri, 2001-12-28 at 06:50, Damian McGuckin wrote:
> 
> In our quest for speed, we inline'd _GetNextChar() and it turns out that
> on a 1000Mhz Pentium, isNewLineChar() is chewing up 10% of the time on
> nextToken().
> 
> I was thinking of inlining all the routines in the anonymous namespace.

Where inlining is showing a tangible performance increase, I certainly
think we should do it.

> Some questions:
> 
> a)	Could we come up some 'ctype' like scheme whereby we assume
> 	that char is signed and we do a table lookup?

I imagine so.

> b)	Alternatively, is a test such as
> 
> 	(isdigit(c) || ('A' <= c && c <= 'F') || ('a' <= c && c <= 'f'))
> 
> 	always valid for a hex digit.

Looks good to me.

> While I fully appreciate that one should get it right before you make it
> fast, we find that if something takes ages to load, be it a VRML file or
> a web page, then users will complain.

I'd like at some point to rewrite our parser to use Spirit instead of
ANTLR. I don't know if that'll end up giving us a speed boost, but I'd
be surprised if it hurt us. (My primary motivation is that I think
Spirit would be a less annoying dependency.) Spirit's still evolving
kinda rapidly, and the ANTLR parser works, so I'm not in a rush to get
this done.

It looks like you're focusing on the scanner here for performance
improvements; and I think any improvements there should help us
regardless of whether we're using ANTLR or Spirit.

-- 
Braden McDaniel                           e-mail: <br...@en...>
<http://endoframe.com>                    Jabber: <br...@ja...>