From: Francois Pottier <Francois.Pottier@inria.fr>
To: Christopher Jeris <cjeris@math.mit.edu>
Cc: caml-list@inria.fr
Subject: Re: [caml] Closures and efficiency
Date: Fri, 29 Oct 1999 11:39:18 +0200 [thread overview]
Message-ID: <19991029113918.23521@pauillac.inria.fr> (raw)
In-Reply-To: <Pine.SUN.4.20.9910261748340.6977-100000@schauder.mit.edu>; from Christopher Jeris on Tue, Oct 26, 1999 at 06:06:28PM -0400
Hello,
> Here's the nub of my question. In a typical synth architecture there are
> very many parameters which take values 0..127. If I had a function
>
> int_subrange_encoder: int -> int -> param_value -> bytestring
>
> which took the bounds of a subrange and generated an encoder function for
> values of that subrange, and then in a voice-architecture description I
> had a list of very many records each of which contained an entry
>
> int_subrange_encoder 0 127
>
> would I suddenly have six million little closures, or would the compiler
> do common-subexpression elimination on them ?
I don't know if the compiler performs CSE for expressions which involve
function applications (it would have to prove that the function
int_subrange_encoder does not perform side effects, which I think
it doesn't -- but I could be wrong).
However, if you're worried by memory consumption, you can easily create
a memoizing version of int_subrange_encoder. Here is a generic "memoize"
function which accepts any 1-parameter function f and returns a
memoizing version of it. (You can adapt it for 2 arguments if you wish,
or uncurry the function int_subrange_encoder, as I have done below.)
let memoize f =
let table = Hashtbl.create 1023 in
fun argument ->
try
Hashtbl.find table argument
with Not_found ->
let result = f argument in
Hashtbl.add table argument result;
result
Of course, memoizing a function f only makes sense if it is applicative,
i.e. it returns the same result when applied twice, and it performs no
observable side effects. You can write:
let int_subrange_encoder (x, y) =
...
let memoized_int_subrange_encoder =
memoize int_subrange_encoder
Hope this helps,
--
François Pottier
Francois.Pottier@inria.fr
http://pauillac.inria.fr/~fpottier/
prev parent reply other threads:[~1999-10-29 17:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-10-26 22:06 Christopher Jeris
1999-10-29 8:56 ` Xavier Leroy
1999-10-29 9:39 ` Francois Pottier [this message]
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