You can cut another 15-ish % from that loop by making an inline loop, btw
(let loop ((pos 0))
(when (< pos (string-length str))
...
(loop (1+ pos)))
I have been looking at the disassembly, even for simpler cases, but I haven't
been able to understand enough of it.
BTW: string-for-each is in the default environment, and is probably the same as
the srfi-13 C implementation.
--
Linus Björnstam
On Sun, 7 Jun 2020, at 08:27, Aleix Conchillo Flaqué wrote:
> Hi,
>
> in the latest guile-json, 4.1.0. I changed some code to use
> for-each+string->list. The performance seemed nice and I released it.
>
> Christopher Lam pointed out that I could have used string-for-each instead.
> I made the change but the performance degraded a lot:
>
> string-for-each:
>
> scheme@(json parser)> ,t (->bool (scm->json-string json))
> $19 = #t
> ;; 17.909537s real time, 18.063382s run time. 0.207281s spent in GC.
>
> vs
>
> for-each + string->list:
>
> scheme@(json parser)> ,t (->bool (scm->json-string json))
> $20 = #t
> ;; 2.998381s real time, 3.319349s run time. 0.471969s spent in GC.
>
> string-for-each is implemented in scheme here, if Im not wrong:
>
> http://git.savannah.gnu.org/cgit/guile.git/tree/module/rnrs/base.scm#n89
>
> string->list and for-each would use C.
>
> Is that huge gap expected?
>
> This is with Guile 3.0.2.
>
> Best,
>
> Aleix
>
