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From: Alexandre Pilkiewicz <alexandre.pilkiewicz@polytechnique.org>
Date: Mon, 7 Mar 2011 13:00:20 +0100
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To: Arlen Cuss <celtic@sairyx.org>
Cc: caml-list@inria.fr
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Subject: Re: [Caml-list] Hashtbl: find and find_rec

Hi

2011/3/7 Arlen Cuss <celtic@sairyx.org>:
> Hi all,
>
> I'm puzzling over the OCaml source, and am trying to work out the reason
> for the following definition:

[snip]

> My only guess thus far is that it's cheaper if we don't recurse (stack
> doesn't grow as much, fewer branches), and thus a few levels of testing
> are put in for good measure to speed up the case where it's one of the
> first three items.
>
> Is this it? Or am I missing something else?

I don't think stack is smaller since the find_rec function is tail
recursive. So it is basically loop unrolling (fewer branches).

What I don't really understand is why only do the unrolling on the 3
first iterations. As soon as we have an unrolled version, why not
calling it recursively?