From: Dmitry Bely <dmitry.bely@gmail.com>
To: Caml List <caml-list@inria.fr>
Subject: Re: [Caml-list] Optimizing Float Ref's
Date: Wed, 31 Mar 2010 23:18:36 +0400 [thread overview]
Message-ID: <g2l90823c941003311218o21b3c207tfea7b3984f5ee93b@mail.gmail.com> (raw)
In-Reply-To: <4BB39B7C.6050402@frisch.fr>
On Wed, Mar 31, 2010 at 10:59 PM, Alain Frisch <alain@frisch.fr> wrote:
> On 31/03/2010 19:21, Dmitry Bely wrote:
>>
>> On Thu, Sep 3, 2009 at 1:44 PM, Xavier Leroy<Xavier.Leroy@inria.fr>
>> wrote:
>> (...)
>>>>
>>>> But, I thought that float ref's were automatically unboxed by the
>>>> compiler
>>>> when they didn't escape the local context.
>>>
>>> Yes, if all uses of the float ref are unboxed, which is the case in
>>> your code.
>>
>> let max_val (a:float array) =
>> let m = ref min_float in
>> for i = 0 to (Array.length a) - 1 do
>> if a.(i)> !m
>> then m := a.(i)
>> done;
>> !m
>>
>> !m is not unboxed (Ocaml 3.11). Should it?
>
> As far as I can tell, the boxing for the reference cell is removed by the
> compiler (that is, the reference is implemented as a mutable local
> variable), but not the boxing for the float contained in the reference.
> Since a is a float array, it is needed to box the float before putting it in
> the reference, hence the allocation.
Hmm, my interpretation of Xavier's words was that the compiler would
completely optimize out memory allocation and keep !m in register. I
can live with the allocation but not at every iteration... How to
rewrite the function to get rid of it? My best achievement so far is
let max_val (a:float array) =
let m = [|-.min_float|] in
for i = 0 to (Array.length a) - 1 do
if a.(i) > m.(0)
then m.(0) <- a.(i)
done;
m.(0)
but it looks ugly...
- Dmitry Bely
next prev parent reply other threads:[~2010-03-31 19:18 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-28 20:32 Will M Farr
2009-08-30 19:43 ` [Caml-list] " Yaron Minsky
2009-08-31 14:09 ` Till Varoquaux
2009-08-31 14:51 ` Will M Farr
2009-08-31 17:30 ` Jon Harrop
2009-08-31 17:15 ` Jon Harrop
2009-09-03 9:44 ` Xavier Leroy
2009-09-03 10:15 ` Will M Farr
2010-03-31 17:21 ` Dmitry Bely
[not found] ` <p2tc7e4e9f1003311055xce0919wac2118aa3c05f1cb@mail.gmail.com>
2010-03-31 18:28 ` Dmitry Bely
2010-03-31 18:59 ` Alain Frisch
2010-03-31 19:18 ` Dmitry Bely [this message]
[not found] ` <m2lfbd71dab1003311252v5bda5d13vc2146d2d24270847@mail.gmail.com>
2010-03-31 20:00 ` Dmitry Bely
2010-04-14 18:13 ` Goswin von Brederlow
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