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Re: Guile's time execution issues
From: |
Linus Björnstam |
Subject: |
Re: Guile's time execution issues |
Date: |
Mon, 04 May 2020 20:47:47 +0200 |
User-agent: |
Cyrus-JMAP/3.3.0-dev0-351-g9981f4f-fmstable-20200421v1 |
Sorry, sent a premature reply. The problem is that some of those match blocks
expand to using equal? which is a lot slower than using eqv? If we are doing it
on every char in a 24mb file we are getting some serious constant factors.
match is a syntax-rules macro, so distinguishing literals are not possible.
Concerning "the macro writer's bill of rights" I could maybe think this it
would be a rather nice thing to turn equal? to eqv? when one argument is a char
literal :D
--
Linus Björnstam
On Mon, 4 May 2020, at 11:36, Ludovic Courtès wrote:
> Hey!
>
> Aleix Conchillo Flaqué <address@hidden> skribis:
>
> > So weird I'm getting different numbers on 2.2.7. Not sure how I'm getting
> > those initial ~20s and you are getting consistent ~ 45s. It
> > shouldn't have nothing to do with it, but could it be I'm running it on
> > macOS?
>
> Did you add this ‘->bool’ call to ensure the resulting alist is not kept
> in memory?
>
> > Now, it would be good to profile ‘json->scm’ to see if there’s anything
> > that could be improved on the Guile side, or if it’s just a normal
> > profile for GC-intensive code.
> >
> > Good news is that I have been working on performance improvements and
> > json->scm is going down from my ~19 seconds to ~3
> > seconds on the same sample file. Linus Björnstam was the one to bring up
> > performance issues so we've been back and forth trying to
> > make it fast.
>
> Nice!
>
> > One thing I found is that `match` is slow. The code looked nicer but had to
> > change it back to lets and conds as the performance
> > increase was ~2 seconds.
>
> Oh, in which case exactly? And are you sure your hand-written code is
> equivalent to the ‘match’ code (it’s common for hand-written code to be
> more lax than ‘match’)?
>
> One thing to pay attention to is the use of ‘list?’, which is O(N), and
> is implied by ellipses in ‘match’. If you want to use ‘match’ in a way
> that avoids ‘list?’, write patterns such as (a . b) instead of (a b ...).
> It doesn’t have the same meaning, but often the end result is the same,
> for instance because you’ll later match on ‘b’ anyway.
>
> (I wish we can one day have a proper list type disjoint from pairs…)
>
> Thanks,
> Ludo’.
>
>