According to my very limited understanding, luatex is generally slower than pdftex because the font loading is more involved [1,2,3,4]. In pdftex, compilation can be sped up by precompiling a preamble to a format, which loads much faster. To my understanding precompiled formats are not that useful in luatex due to mixing of tex- and lua-code. [5]
As I'm probably not the only one that writes many more short math-oriented notes than complete books, the startup speed of luatex is an issue. I resisted the switch from pdftex to luatex very long because of this. How hard would it be to make a luatex compatible precompiled format? One that basically serialises the whole luatex state to a file and could re-use it? Would it speed up the compilation of short documents? Is there any plans or projects related to this? Best regards and season's greetings, thank you for the wonderful tools you have brought us! Henrik Mannerström [1] https://tex.stackexchange.com/questions/690903/format-dumping-using-lualatex-and-mylatexformat [2] https://tex.stackexchange.com/questions/114742/speeding-up-compilation-using-precompiled-preamble-with-luatex [3] https://tex.stackexchange.com/questions/75118/why-does-it-take-lualatex-so-long-to-load-fonts-and-can-i-speed-it-up [4] https://tex.stackexchange.com/questions/234757/why-is-lualatex-so-slow-and-is-there-anything-i-can-do-about-it [5] https://tex.stackexchange.com/questions/324559/guidelines-for-using-mylatexformat-with-luatex
