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From: "François Pottier" <francois.pottier@inria.fr>
To: jean-marc.alliot@irit.fr, caml-list@inria.fr
Subject: Re: [Caml-list] Choosing a random element in a Map or a Set
Date: Thu, 18 Mar 2021 11:06:39 +0100
Message-ID: <368aa12e-e819-4049-7ec5-4a3479f77bbb@inria.fr> (raw)
In-Reply-To: <3e61c49d-8b20-378b-0c24-75b8da14b4f7@alliot.org>

Le 18/03/2021 à 10:44, jean-marc.alliot@irit.fr a écrit :
> 1) Is there another, more intelligent, solution?
> 2) Is my solution biased? I think it is not, as long as the tree is
> properly balanced but...

The tree is only approximately balanced, so this approach should be
OK if you are willing to accept some bias, but it is not perfectly
uniform.

If it is important to obtain a uniform distribution, then I would
suggest: 1- picking a random index in the interval [0, n); and 2-
using a data structure that allows efficient indexing. Finger trees
come to mind (see the papers by Hinze and Paterson and by Sozeau),
but there are probably others.

-- 
François Pottier
francois.pottier@inria.fr
http://cambium.inria.fr/~fpottier/

  reply	other threads:[~2021-03-18 10:07 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-18  9:44 jean-marc.alliot
2021-03-18 10:06 ` François Pottier [this message]
2021-03-18 14:20   ` Simon Cruanes
2021-03-18 17:06     ` jean-marc.alliot
2021-03-18 11:10 ` Nicolas Barnier
2021-03-18 11:32   ` François Pottier
2021-03-19  1:32   ` Francois Berenger
2021-03-18 12:34 ` Ivan Gotovchits
2021-03-18 12:48 ` Ivan Gotovchits

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