[metapost] memory problem

Stephan Hennig mailing_list at arcor.de
Fri May 5 01:10:11 CEST 2006

Taco Hoekwater schrieb:

> I have to look this up to be sure, but I strongly suspect that what
> happens is this: for each new equation, metapost runs through the
> complete list of variables to see if its status has changed thanks
> to the new equation. If you have a lot of 'not known' variables,
> this process can become very slow.

Taco, thanks for your reply! Your idea sounds plausible. Since equation
solving is /the/ feature of MetaPost such a fundamental performance leak
would be very annoying. Remember, I'm just drawing a couple of boxes. :(

As far as I know -- from reading this list or comp.text.tex --
MetaPost's memory management is a mess (the code). So I do not expect
substantial improvements in that area in the near future. (Please prove
me wrong.)

What about a new MetaPost option that lets one turn off equation
solving? This would save the time to scan the list of 'not known'
variables while one builds equation systems that are known not to have a
unique solution currently. Only after switching equation solving on
again the 'not known' list is scanned and all solvable variables are
removed. This doesn't help much if you have many unsolved variables and
need to solve another small equation system. In that case the long 'not
known' list is scanned since equation solving needs to be turned on.
However, I think if such an option would be supported by MetaObj's
constructors applications such as given in the example would benefit.
What do you think?

Stephan Hennig

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