Re: Plan for discussions

[Han-Wen Nienhuys]

On Mon, May 14, 2012 at 3:04 AM, David Kastrup <address@hidden> wrote:
>
> "address@hidden" <address@hidden> writes:
>
> > One idea I've been a fan of for a long time is some type of aux file
> > system in LilyPond.  That is, if we can come up with a file format
> > that stores loads of data from previous runs of a score and then can
> > somehow compare it to a parsed file, it could cut compilation time
> > down by about 1/5 for stuff like changing B to B-flat in the Mahler's
> > 9th.  I say 1/5 because the line breaking would need to be redone,
> > which means everything afterwards needs to be redone, but the
> > interpretation stage could likely be cut down.
>
> The interpretation stage does not take 80%.  If you want to speed it up
> significantly, work on the input system.  LilyPond spends most of its
> time IIRC in the routine reading a single character, because parser and
> Scheme read routines are more or less working independently and are
> exercised in parallel all the time.  Stuff in lexer.ll like
..
> where a new string is getting allocated for every rest.  There is a lot
> of potential for streamlining stuff before one caches it.

Run a profile. These examples may not be the pinnacle of elegance, but
unless you can measure it makes any difference, we shouldn't bother
optimizing it.

--
Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen