[luatex] Removing the zero-initialization of an array can speedup LuaTeX on plain TeX document by 25%

[Joseph Wright]

On 01/09/2024 09:07, Hans Hagen wrote:
>> Regarding performance tests, there are a few things worth to be
>> mentioned.  You get different results in different environments.
>> First of all, in TeX Live luatex.ini contains the line
>>
>>    \input load-unicode-data.tex
>>
>> This huge file blows up the format file and increases startup time
>> significantly.  AFAIK it's currently only used by LaTeX and can be safely
>> removed from all plain TeX formats.
>
> Isn't there also that file that uses \pdfglyphtounicode ? I don't use it
> but loading the 50 K lines file could be sped up a bit.

No, that is not read by the standard luatex.ini file or any of the
subfiles (including load-unicode-data.tex).

>> With the setup decribed above I can compile a "hello world" with
>> Knuth's TeX within 13 ms and "The TeXbook" (285 pages) in less than
>> 190 ms.
>
> What system? Luatex or pdftex?
>
>> But it would take much longer with load-unicode-data.tex in the format
>> file and a complete TeX Live installation.
>
> Depends on what load-unicode-data does, but a bit bigger format
> shouldn't matter that muchm should it? We're not suddenly in the seconds.

 From my tests, format file size makes very little different to start up
time (this came up recently for LaTeX, and the impact is pretty tiny).

Joseph