[luatex] using (pdf)lualatex

[Hans Hagen]

Yue Wang wrote:

> - When the font cache is given, LuaTeX seems to use too much memory
> (It usually used up to 600M when typeset a document with only 3
> Chinese fonts (song,hei,kai)). And this problem is solved by Taco and
> Hans several month ago by changing the Lua C source code. However, the
> memory footprint is still a little bit large (more than 300M for 3
> Chinese fonts). It will take 3-4 seconds on my machine to load the
> font cache for three Chinese fonts.

no matter what speedups we are able to cook up in the future, keep in 
mind that the nature of luatex is that information is passed around in 
lua tables and this will not change; as a result luatex will always have 
a larger footprint than pdftex and xetex; for that reason it's good to 
have multiple engines: xetex is faster and uses less memory (although it 
has some pretty large usage as well) but has kind of frozen interfaces 
while luatex is more open with respect to interfaces but at the cost of 
speed and memory (as soon as one starts to do fancy things with node 
lists, not only memory usage but also procesing speed compared to the 
other tex engines becomes a factor); it's simply something that luatex 
users to accept

> - When the font cache is not given, ConTeXt will try to dump one on
> the first run. LuaTeX will use much more memory than expected. For
> example, only loading the metrics from an ordinary Chinese font like
> AdobeSongStd-Light (a 13M font) in plain TeX will use more than 700M
> memory. I reported this problem to the ntg-context mailing list
> yesterday.

btw, the table of that font is not even that large:

  7.623.626 adobesongstd-light.lua

when dumped and when compiled to byte code:

  3.833.022 adobesongstd-light.luc

when loading this font, it takes soem 25 meg

> For a normal publication, usually some 5 or 6 Chinese fonts will be
> used. In some cases dozens of these fonts might be used. So it will
> take very long time for luatex to parse the fonts, as well as huge
> memory to store the metrics data. So it is suggested that users who
> want to try luatex should have a computer with large memory and fast
> CPU since the fontforge library is a nightmare for Asian users who
> have old machines.

by the time that luatex is mature (a couple of years down the road) 
machines have much more memory so memory is no issue then; disks might 
be solid state which also helps; processors might not be faster but 
caching migh be better; but no matter what the future brings ... luatex 
will never be real fast

(btw, cjk fonts might be large in number of glyphs, but for instance 
arabic has way more features so there processing time is more an issue)

Hans

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