[antlr-interest] Serious doubts on usage of incremental parsinginides

[Prashant Deva]

Scott,
> 
> AFAICS, the user can only be editing one thing at a time, so there's really
> only one model to update (no matter how many views on that model). Unless
> you have a very slow machine or very low RAM causing swapping, this should
> be pretty much unnoticeable.

Again you are not getting me.
Lets say we have the following which needs to be updated on every keystroke- 
1.) Tree View
2.) Search results view
3.) 3d (hell, lets say OpenGL) dig 
4.) Editor highlighting
5.) Symbol table entries
6.) Auto indentation
7.) Folding structure 

Now if you are going to update all these things on every single
keystoke  ,then the editor is gonna seem real slow.

And mind you if you don't run the parser on every keystroke, then you
are limiting its power to as good as a batch parser.
Hell, a batch parser also takes jsut arnd 30 ms to parse a 10,0000
line file, and we are going to be updating after say 500ms anyway, so
what diff does it make whether we run a batch parser in between or an
incremental parser.

As you are talking so much about eclipse, well look at the source.
they run a FULL parse each time, and just get the deltas of the diff
between 2 asts.
They DONT have an incremental parser.

Take a look at 'JavaSourceViewerConfiguration', in the getReconciler()
method. Hell even the reconciler there is not incremental. There
stands no question of incremental parsing.

They just do incremental compilation, for which they anyway have to
parse the full file, and as its done only each time you save, the
little slowness does not get noticed.

So here is my problem stated once again -
You can't run an incremental parser on every keystroke cause no matter
how fast the parser is, the amount of 'other' stuff to update will
slow the editor.
If you can't run the parser on each keystroke, the incremental parser
is as good as a batch parser cause the time interval you are gonna run
it in, you can run the batch parser 10 times in it anyway.

So what's the use of an incremental parser.

Also i was looking at this blog of the guy who handles intellisense in
visual studio. even they don't run their parser on each keystroke,
cause it will be too slow.
And eclipse is not fast! its just that parsing is not that slow after all ;)

PRASHANT


On 4/25/05, Scott Stanchfield <scott at javadude.com> wrote:
> Ahhh... I took "incremental parsing" for "incremental compilation".
> 
> Never mind ;)
> 
> AFAICS, the user can only be editing one thing at a time, so there's really
> only one model to update (no matter how many views on that model). Unless
> you have a very slow machine or very low RAM causing swapping, this should
> be pretty much unnoticeable.
> 
> I guess I'll come back to eclipse anyway. I've never noticed it stopping me
> just because it's updating its ast. Occasionally I'll have to wait a few
> seconds for a large build (due to some validation weirdness in the
> webtools), but even that's minimal.
> 
> I'm not sure if eclipse is totally rebuilding the ast each time or not (it
> may be). I'm working on a plugin that filters trivial get/set methods and
> displays an editable table of bean properties (which is why I want the ANTLR
> tree support to be more flexible), and I had it rebuild the ast each time
> and it wasn't noticeable to me. (In other words, the ast build was getting
> called at least twice per refresh; once by eclipse, once by me. However,
> eclipse may be caching it and detecting changes so it can simply return it).
> 
> Later,
> -- Scott
> 
>