From: malc <malc@pulsesoft.com>
To: "Marcin 'Qrczak' Kowalczyk" <qrczak@knm.org.pl>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Benchmark: ref update vs argument passing
Date: Wed, 21 Nov 2001 03:20:12 +0300 (MSK) [thread overview]
Message-ID: <Pine.LNX.4.21.0111210301370.6981-100000@oyster> (raw)
In-Reply-To: <slrn9vlqj1.cj1.qrczak@qrnik.zagroda>
On Tue, 20 Nov 2001, Marcin 'Qrczak' Kowalczyk wrote:
> Wed, 21 Nov 2001 01:35:53 +0300 (MSK), malc <malc@pulsesoft.com> pisze:
>
> >> let use_refs' time =
> >> let rif = ref 0 in
> >> for i = 0 to time - 1 do rif := !rif + 1 done;
> >> !rif
> > let use_refs' time =
> > let rif = ref 0 in
> > for i = 0 to pred time do incr rif done;
> > !rif
>
> The generated code is exactly the same :-P
Precisely ;) It's more "camlish" in my opinion, which is why i couldnt
resist posting it.
>
> But none of the following produces optimal code (judging by looking
> at the generated code):
>
> let current = ref 0
> let next1 () = let x = !current in incr current; x
> let next2 () = let x = !current in current := x + 1; x
> let next3 () = incr current; !current
> let next4 () = let x = !current + 1 in current := x; x
>
> Moreover, making the counter private on the declaration level:
>
> let next1 =
> let current = ref 0 in
> fun () -> let x = !current in incr current; x
>
> yields worse code, even though the semantics is the same.
Semantics are not the same here: first 'current' is module global and
statically allocated in module storage. Second 'current' is lexically
bound.
When i was playing with Doug Bagley's "Great Computer Language Shootout"
http://www.bagley.org/~doug/shootout/bench/sumcol/ , i found that no
matter how hard i try to invent some ingenious summing function caml
generated code leaves a lot to be desired. (I think this holds for any
use of global references).
P.S. When playing with those functions you might find -dcmm option
useful.
--
mailto:malc@pulsesoft.com
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next prev parent reply other threads:[~2001-11-21 0:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <9teme6$bn2$1@qrnik.zagroda>
2001-11-20 23:42 ` Marcin 'Qrczak' Kowalczyk
2001-11-21 0:20 ` malc [this message]
[not found] <9tdsbg$qjc$1@qrnik.zagroda>
2001-11-20 15:37 ` Marcin 'Qrczak' Kowalczyk
2001-11-20 22:35 ` malc
2001-11-20 15:11 Stefano Zacchiroli
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