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Re: Lilypond performance

From: David Kastrup
Subject: Re: Lilypond performance
Date: Tue, 10 Aug 2010 11:32:06 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux)

Urs Liska <address@hidden> writes:

> Well, this seems a misunderstanding, mainly due to my English and the
> fact, that I only have very intermediate programming experience with
> very little theoretical background.
> I think basically we want to say the same thing :-)

I consider this extremely unlikely.

> I don't find it natural to "walk through" the music from beginning to
> end.

I should think that this is the only reasonable direction.  And indeed,
this is what Lilypond essentially does (or did at one time), keeping and
maintaining a pruned tree of possibilities as an internal data
structure.  Keeping the width of the maintained parts of the tree pruned
to a maximum width is the art of linear programming.

> What I wanted to say is: Only if this would be possible one could
> expect a linear increase in processing time with longer scores.  As it
> is not possible I find it "natural" that processing time increases
> exponentially.

I suggest you make yourself acquainted with "linear programming".  It is
not likely that we get to understanding each other when working from
incompatible theoretic assumptions.

> Maybe there are possible algorithms to substantially simplify or
> streamline the tasks lilypond has to do - I don't have the theoretical
> background to tell.
> But if it's not possible (which I assume), all I wanted to say is that
> you can only work around the problem with better hardware.

Again: you can't work around exponential complexity for problems of
variable size with "better hardware".  If you think otherwise, you are
likely employing "exponential complexity" as a buzzword rather than in
its actual meaning.

David Kastrup

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