\input gets slower after each \input

Phelype Oleinik phe.h.o1 at gmail.com
Wed Apr 28 16:12:04 CEST 2021

On 27/04/2021 19:59, Karl Berry wrote:
>      inputs that file 10000 times
> Is there a practical problem with the slowdown?  E.g., LaTeX nowadays
> calls \scantokens hundreds of thousands of times?  -k

No, we avoid that whenever possible (the first usage will get to the
kernel with the next -dev release, and it will be rarely used).

Actually I spotted this behaviour when doing some benchmarks including
|\input| and I noticed that a supposedly faster code was running much
slower, and it took me quite a while to find out that |\input| was
messing up my benchmarks, so my main problem was that I didn't know that
this was happening.

The practical issue is that any document in general gets slower if there
are more packages loaded, especially now that expl3 is preloaded in the
LaTeX kernel, or when big packages like fontspec, unicode-math or TikZ
are loaded...  But I really don't know how much or how noticeable is
this difference...


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