Re: guile 3 update, september edition

[Andy Wingo <wingo@pobox.com>]

Greets :)

On Mon 17 Sep 2018 11:35, ludo@gnu.org (Ludovic Courtès) writes:

>> The threshold at which Guile will automatically JIT-compile is set from
>> the GUILE_JIT_THRESHOLD environment variable.  By default it is 50000.
>> If you set it to -1, you disable the JIT.  If you set it to 0, *all*
>> code will be JIT-compiled.  The test suite passes at
>> GUILE_JIT_THRESHOLD=0, indicating that all features in Guile are
>> supported by the JIT.  Set the GUILE_JIT_LOG environment variable to 1
>> or 2 to see JIT progress.
>
> Just to be clear, does GUILE_JIT_THRESHOLD represents the number of
> times a given instruction pointer is hit?

No.  It is an abstract "hotness" counter associated with a function's
code.  (I say "function's code" because many closures can share the same
code and thus the same counter.  It's not in the scm_tc7_program object
because some procedures don't have these.)

All counters start at 0 when Guile starts.  A function's counters
increment by 30 when a function is called, currently, and 2 on every
loop back-edge.  I have not attempted to tweak these values yet.

>> Using GNU Lightning has been useful but in the long term I don't think
>> it's the library that we need, for a few reasons:
>
> [...]
>
> It might be that the lightning 1.x branch would be a better fit (it was
> exactly as you describe.)  I think that’s what Racket was (is?) using.

Could be!  I will have a look.

Cheers,

Andy