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Re: [Texmacs-dev] Darcy's plan for GNU TeXmacs 2.1.1

From: Massimiliano Gubinelli
Subject: Re: [Texmacs-dev] Darcy's plan for GNU TeXmacs 2.1.1
Date: Tue, 30 Nov 2021 23:35:47 +0100

Hi all,

 thanks for taking up the work on S7. I make some short remarks:

1) please be aware that S7 is constantly updated by its creator, I usually keep 
in sync with the upstream here 


2) The version in TeXmacs has just a small patch in the symbol resolution 
routine which otherwise is too slow for TeXmacs. 

3) The creator is very responsive to any input, I think if we patch S7 that we 
try to send our feedback upstream so that we do not diverge too much from the 
reference implementation

4) At some point I wanted to try also another scheme: femtolisp


But I still haven't found the time to intergrate it. 

5) One problem with Guile 3.0 is that it is not supported on Windows, so in 
case we go for it we will have to patch it in order to compile. What I do not 
like in Guile is that it is too large for our need, we essentially would like 
that all I/O or OS interaction is done via TeXmacs (which then goes via Qt5) so 
we should not have compatibility problems in the Qt layer.


> On 25. Nov 2021, at 16:41, Joy Yang Qiping via Texmacs-dev 
> <texmacs-dev@gnu.org> wrote:
> Hi Joris,
>> About plans for Scheme.  After the benchmarks, I got somewhat confused.
>> If S7 were systematically faster than Guile (at least than Guile 1.8),
>> then I think that moving to S7 is the simplest option for us.
>> Otherwise, we should keep playing with Guile 3 too.
>> If my understanding is correct, then the main problem is the LaTeX export.
>> Does anyone understand why this is so much slower with S7?
>> Another decision we could make is that we wish to keep the support
>> for various versions of Scheme.  But then we would need a branch that
>> works for both S7 and Guile 3.
> Moving to S7 may not be as simple as we would like. Here is another issue 
> that troubles me. Over my own usage experience, TeXmacs under S7 could 
> consume more memory than I would like (over 1GB for single document editing).
> I think S7 will benefit from a more sophisticated gc implementation. From 
> what I have seen through the code, they are using the same memory pool for 
> every scheme object, which isn’t ideal for TeXmacs. Since TeXmacs not only 
> has a linear growth of persistent object, e.g., edit history for instance, 
> during editing, but also has a lot of side computations that claims some 
> memory for a short duration. This means the gc will often get triggered and 
> are slower and TeXmacs will benefit from having several levels of memory 
> pools (from persistent to short-lived) to adapt to different memory usage 
> pattern. The memory pool grows exponentially. I have tried to tune its 
> exponential parameter from 2 to 1.2~1.5. But from what I have observed, it 
> only delays the inevitable. The current S7’s gc implementation cannot 
> guarantee long-term stability of TeXmacs — memory consumption will grow to a 
> very high level. I don’t think it is a good idea to go through with S7 as is. 
> I could try to turn that into a linear growth, which should work fine for 
> TeXmacs in most cases (I’m guessing). But it really isn’t meant to be a 
> general purpose scheme implementation with those changes. We could also find 
> ways to reduce those persistent memory throughout editing. I might also try 
> to look for some parameters within TeXmacs that affect those (how many 
> editing history to keep for instance) and see if it helps.
> I think it would be better to keep both S7 and Guile 3 working for now. Right 
> now the main problem with Guile 3 is Windows support. Neither is the perfect 
> solution for us :(
> Best regards,
> Joy
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