From: "Linus Björnstam" <linus.internet@fastmail.se>
To: guile-user@gnu.org
Subject: Re: Pure (side-effect-free) calls into c/c++?
Date: Sat, 11 Jan 2020 18:40:14 +0100 [thread overview]
Message-ID: <365fc4d0-8c2e-4578-b38f-05ebf6c20064@www.fastmail.com> (raw)
In-Reply-To: <CAHrUA357t4jtHCOxO+vMMyYZuFxtXYBPAtW8aZJ2KvNRDmBC5Q@mail.gmail.com>
I have a macro called lambda/memo and define/memo for these situations: https://hg.sr.ht/~bjoli/misc/browse/default/memoize.scm
If the function gets called with a gazillion different arguments the memoizatiin hash gets large, and there are no mechanisms to stop that from happening. It also lacks a fast path for single argument functions.
You can disregard the repo license. Use that function is you like, if you like to.
--
Linus Björnstam
On Fri, 10 Jan 2020, at 23:36, Linas Vepstas wrote:
> So, I've got lots of C code wrapped up in guile, and I'd like to declare
> many of these functions to be pure functions, side-effect-free, thus
> hopefully garnering some optimizations. Is this possible? How would I do
> it? A cursory google-search reveals no clues.
>
> To recap, I've got functions f and g that call into c++, but are pure (i.e.
> always return the same value for the same arguments). I've got
> user-written code that looks like this:
>
> (define (foo x)
> (g (f 42) (f x) (f 43))
>
> and from what I can tell, `f` is getting called three times whenever the
> user calls `foo`. I could tell the user to re-write their code to cache,
> manually: viz:
>
> (define c42 (f 42))
> (define c43 (f 43))
> (define (foo x) (g c42 (f x) c43))
>
> but asking the users to do this is .. cumbersome. And barely worth it: `f`
> takes under maybe 10 microseconds to run; so most simple-minded caching
> stunts don't pay off. But since `foo` is called millions/billions of times,
> I'm motivated to find something spiffy.
>
> Ideas? suggestions?
>
> -- Linas
> --
> cassette tapes - analog TV - film cameras - you
>
next prev parent reply other threads:[~2020-01-11 17:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 22:36 Pure (side-effect-free) calls into c/c++? Linas Vepstas
2020-01-11 14:13 ` Zelphir Kaltstahl
2020-01-11 14:38 ` Matt Wette
2020-01-11 18:11 ` Linas Vepstas
2020-01-11 18:52 ` Linas Vepstas
2020-01-11 21:56 ` Taylan Kammer
2020-01-12 2:15 ` Linas Vepstas
2020-01-12 4:12 ` Linas Vepstas
2020-01-12 2:12 ` Linas Vepstas
2020-01-12 3:21 ` Taylan Kammer
2020-01-12 4:32 ` Linas Vepstas
2020-01-12 5:52 ` Linas Vepstas
2020-01-11 17:40 ` Linus Björnstam [this message]
2020-01-12 3:03 ` Christopher Lam
2020-01-12 10:35 ` Linus Björnstam
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