[NTG-context] Re: Why LuaMetaTex is so slow?

[Hans Hagen <j.hagen@xs4all.nl>]

On 1/19/2024 11:00 AM, Henning Hraban Ramm wrote:
> Am 19.01.24 um 10:31 schrieb Hans Hagen:
>> (that said: luametatex runs fine on my mobile phone)
> 
> What’s the smallest/oldest device someone tried LMTX on?
> (We were joking about “Hans’ thermostate and Alan’s fridge“…)
> Would it run on some 8 bit homecomputer? (I’d guess the RAM is too 
> limited, and loading from datasette would need hours…)
> 
> Just curious.
The smallest i have here is a https://en.wikipedia.org/wiki/RCA_1802 
which actually was a very nicely designed thing (also powers the 
hubble); processors never became cleaner. Now, as the kit I used only 
had 512 bytes ram (later 2K or so) it really learns one how to program 
efficiently (thihk of writing a simple game, save and load from cassette 
player, etc in that space; dynamic adaptive functions and such) and you 
know where I'm coming from'(later pascal and modula).

That said: luametatex has a smaller memory footprint than luatex 
although nodes are way bigger but even that won't make it run well on an 
8 bit processor, assuming it can address 32 bit mem.

Context mkii started on 4.7 Mhz intel (386) so now we're 1000 times 
faster but performance gain is not linear. After all, tex has to compete 
with other applications running at the same time (browsers, remote 
clients, media apps, web polling apps, zoom, etc.) so it's kin dof 
amazing that it actually performs okay.

What boosted performance is for instance ssd's. What might boost is ddr5 
memory but that has to catch up with ddr4 first. What also boosted 
luametatex is cpu cache. I remember when taco and I moved to the math 
part we noticed a drop in performance, until machines got updated with 
larger cache. We'd just crossed some magic threshold.

Actually, I kind of assume that we're stuck with cpu performance but 
nevertheless luametatex became faster. It helps to develop on an older 
machine and not on a yearly updated one as that obscures matters. (Not 
that I'd not like a faster machine, but that comes at a steep price.)

Hans

ps. In the tranmsition from pdftex to luatex to luametatex one should 
not underestimate Taco's effort of going from basically unreadable and 
useless C output by web2c (pascal -> c) to what became the luatex C code 
base (with embedded original documentation). From that we added more 
functionality gradually over a decade till luametatex spun off, which 
then lead to quite a bit of refactoring again (but trying to maintain 
the spirit of how tex is programmed).


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