From: William Chesters <williamc@paneris.org>
To: <caml-list@inria.fr>
Subject: [Caml-list] OCaml Speed for Block Convolutions
Date: Mon, 4 Jun 2001 21:51:36 +0200 (CEST) [thread overview]
Message-ID: <15131.59080.327155.47983@beertje.william.bogus> (raw)
In-Reply-To: <002f01c0ecf9$d028a3b0$210148bf@dylan>
David McClain writes:
> ....well, I hate to say this... but I did recode the innermost loop in C and
> it now runs more than 5 times faster... Straight recoding into C bought 4x,
> and using better math brought that up to 5x.
>
> I think the big thing here is that the OCaml code was producing huge amounts
> of garbage, despite preallocated buffers with which all the processing was
> reading and writing data. The ancillary closures and tuple args were just
> eating my shirt...
I can easily imagine that, with two caveats: tuples passed directly to
functions do seem to get elided, while on the other hand apparently
atomic float accumulators can cause more garbage than you might think.
E.g.
let a = ref 0. in
for i = 0 to n-1 do
a := !a +. Array.unsafe_get xs i
done
makes garbage---`a' isn't unboxed---while
type floatref = { mutable it: float }
let a = { it = 0. } in
for i = 0 to n-1 do
a := !a +. Array.unsafe_get xs i
done
doesn't. The effect on the visible quality of the assembler for the
inner loop is dramatic, and so is the speed improvement ... basically
using polymorphic data structures is a bad idea. I wonder if this is
a limitation you have run up against?
Some years ago I made a library using camlp4 for supporting tensor
notation, e.g.
tens x[I] = a[I J] b[J]
using both automatically generated C and vanilla caml. When I
recently noticed the above point about not using polymorphic
references, I found there was rather little difference in performane
between the C and ocaml versions.
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next prev parent reply other threads:[~2001-06-04 19:47 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-04 13:25 David McClain
2001-06-04 19:51 ` William Chesters [this message]
2001-06-04 20:05 ` Chris Hecker
2001-06-04 20:15 ` David McClain
2001-06-04 22:34 ` Markus Mottl
2001-06-06 20:13 ` William Chesters
2001-06-06 22:29 ` Chris Hecker
2001-06-07 7:42 ` William Chesters
2001-06-05 7:22 ` Chris Hecker
2001-06-06 6:27 ` David McClain
2001-06-04 22:14 ` Tom _
2001-06-04 22:57 ` Chris Hecker
2001-06-05 2:52 ` Brian Rogoff
2001-06-05 15:02 ` Stefan Monnier
2001-06-05 10:48 ` Tom _
2001-06-06 2:03 ` Hugo Herbelin
2001-06-06 4:04 ` Charles Martin
2001-06-06 18:25 ` William Chesters
2001-06-06 18:35 ` William Chesters
2001-06-06 18:40 ` Patrick M Doane
2001-06-07 1:50 ` Hugo Herbelin
2001-06-07 18:20 ` Tom _
2001-06-07 23:49 ` [Caml-list] let mutable (was OCaml Speed for Block Convolutions) Jacques Garrigue
2001-06-08 0:20 ` [Caml-list] Currying in Ocaml Mark Wotton
2001-06-08 10:13 ` Anton Moscal
[not found] ` <Pine.LNX.4.21.0106081015000.1167-100000@hons.cs.usyd.edu.a u>
2001-06-08 0:38 ` Chris Hecker
2001-06-08 8:25 ` [Caml-list] let mutable (was OCaml Speed for Block Convolutions) Ohad Rodeh
2001-06-08 15:21 ` Brian Rogoff
2001-06-08 17:30 ` Pierre Weis
2001-06-08 18:36 ` Stefan Monnier
2001-06-08 19:07 ` Pierre Weis
2001-06-08 19:30 ` Michel Quercia
2001-06-11 6:42 ` [Caml-list] should "a.(i)" be a reference? (was "let mutable") Judicaël Courant
2001-06-11 13:42 ` [Caml-list] let mutable (was OCaml Speed for Block Convolutions) Pierre Weis
2001-06-12 3:21 ` Jacques Garrigue
2001-06-12 7:43 ` Pierre Weis
2001-06-12 8:31 ` Jacques Garrigue
2001-06-12 13:15 ` Georges Brun-Cottan
2001-06-12 21:54 ` John Max Skaller
2001-06-15 9:55 ` Michael Sperber [Mr. Preprocessor]
-- strict thread matches above, loose matches on Subject: below --
2001-06-01 18:38 [Caml-list] OCaml Speed for Block Convolutions David McClain
2001-06-01 22:51 ` Tom _
2001-06-02 0:10 ` Stefan Monnier
2001-06-04 10:12 ` Jacques Garrigue
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