[Dev-luatex] Re: unexplained difference between luatex and luahbtex

20 Jan 2025

      Thank you very much for testing.

I didn't use such tools. I am watching the terminal when fonts are 
downloaded (at the end of the document) and I notice the delay per each 
Besley fonts downloaded from ~/texmf. Sure, it is observable. It looks 
like waiting for some kind of time limit.

Unfortunately, questions remains: why behavior of Lua garbage collector 
differs in luatex and luahbtex when the programs have to do the same?

When we copy the fonts from ~/texmf/fonts to current directory:

    cp ~/texmf/fonts/opentype/besley/* .

and run the test, then the unwanted delay with luahbtex disappears. It 
seems that this has something to do with file searching from TeXmf tree. 
Garbage collector behavior differs when files are in in different locations?

Best regards

Petr Olsak

On 1/20/25 11:12, luigi scarso wrote:
...
On Sun, 19 Jan 2025 at 19:32, luigi scarso  wrote:
On Sun, 19 Jan 2025 at 11:37, Petr Olsak  wrote:
Hello
I am testing new luahbtex and comparing it with luatex because
        I am
        considering to set OpTeX with luahbtex engine instead luatex
        in TeXlive
        2025.
        I have found a difference between lautex and luahbtex behavior
        which I
        am unable to explain why. The difference is shown only when
        huge number of
        fonts are downloaded by luaotfload and only with selected
        fonts from
        internet saved to ~/texmf/fonts. And it manifests only as a
        little delay
        (with luahbtex) during dlownloading the fonts to PDF at the
        end of the
        document visible if you are watching at the terminal. The PDF
        result is
        equal, but I am worried that there is a hidden bug in luahbtex
        because
        the difference is unexpected.
I teseted this with OpTeX macros, they never use mode=harf. So
        I expect the
        same behavior with both engines. The example for testing is
        somewhat more
        complicated and it is exactly described at
https://tex.stackexchange.com/questions/735071/
The main question is: why luatex behaves correctly (with no
        delay during
        downolading fonts) but luahbtex presents a delay in given
        cases? Where is
        the difference? Can the luatex developers explain this?
Thank you
Petr Olsak
under linux
    /usr/bin/time always reports  luahbtex slower of about 5seconds,
    but  I was not able to find why /where.
--
    luigi
Using gprofng
https://sourceware.org/binutils/wiki/gprofng
I can see that luahbtex spends a relevant time on sweeplist, which 
means that the lua gc  plays an important role here.
--
luigi