[luatex] LuaTeX precompilation

[Hans Hagen]

On 12/20/2023 3:48 PM, Axel Kittenberger wrote:
> 
> 
> On Wed, Dec 20, 2023 at 2:31 PM Hans Hagen <j.hagen at xs4all.nl 
> <mailto:j.hagen at xs4all.nl>> wrote:
> 
>     in practice one can neglect the performance drop because computers
>     likely have become (more than) 3 times faster since 2005, when luatex
>     showed up, and at that time pdftex performance was considered okay
> 
> 
> Sorry, but I have to disagree here, for me the performance differences 
> were indeed a dealbreaker for me to push lualatex as a general 
> purpose replacement in my department. (remember the discussion with one 
> patch https://tug.org/pipermail/luatex/2023-June/007824.html 
> <https://tug.org/pipermail/luatex/2023-June/007824.html> but with my 
> general impetus to improve runtime performance I was eventually told to 
> stop when profiling into the Lua part proofed hard).

I don't consider these ipsum test real tests. Who knows how much cpu 
cache is used for a test that does basically nothing. If zip impact is 
an issue, then you can run comprelevel 0. You can also disable synctex 
if enabled.

A useless test with context:

\null / \dorecurse{1000}{\tufte\par} % 233 pages

0.6   / 1.1 seconds pdftex
0.7   / 2.7 seconds luatex
0.5   / 2.6 seconds luametatex
0.8   / 5.5 seconds xetex

the time includes the runner script (so for instance for luametatex the 
real run has < .5 sec startup time). xetex migh tbe slow because of the 
binary (not sure how optimized it is).

In documents of average complexity i normally get 30 page/second 
performance. On more complex documents pdftex can be slower. I have a 
2017 laptop so more modern hardware will gove lower numbers

(I'i do regular perfrmance tests so by now i know pretty well where 
bottlenecks in tex can be)

> Why it may be true, that lualatex may run now in less time on the same 
> document than pdflatex ran 20 years ago, it's still a tall ask for 
> someone to switch from a compiler that uses 150s for a complicated 
> document to one that uses 210s, in this case just for 
> compatibility/simplicity reasons, having to wait a minute longer? Sorry 
> deal breaker. That's why I stuck to pdflatex as default and use lualatex 
> only when one of its more advanced features is absolutely necessary, and 
> to my impression this seems to be a widespread notion.

i can't remember the last time when i needed 150 sec for a run, and can 
live with 10 sec for a 350 page document (if that becomes an issue i 
have to upgrade hardware)

> So in this sense, yes you are right, when you need one of lualatex 
> advanced features it's to be considered okay, as in pdflatex was okay 20 
> years ago, if you do not specifically need it though, then no, stick 
> with pdflatex.
indeed. i suppose that most latex users can just use pdftex, because 
after all the selling point is often 'articles' and such and those 
styles are (i assume ) pretty stable and when the language is english 
there is little to gain from luatex (even 8 bit fonts are okay then)

just use what works best (pdftex will be around for ages); i assume 
latex will become faster over time so maybe in a few years your users 
won't notice a move to luatex

Hans

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