Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!us.feeder.erje.net!news2.arglkargh.de!news.swapon.de!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: hexxial Newsgroups: comp.games.development.programming.algorithms Subject: Re: Shuffling Date: Sun, 20 Jan 2013 22:58:00 +0000 Organization: A noiseless patient Spider Lines: 41 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sun, 20 Jan 2013 22:58:01 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="8897a9449775a0b3f6a1f0a719db28b8"; logging-data="21492"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19sRz21h3H19LH/FNfiuk+bbBbMuZXlN4g=" User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/17.0 Thunderbird/17.0 In-Reply-To: Cancel-Lock: sha1:UeTwUk6H4mzdSrwxP3V2PfHIlFE= Xref: csiph.com comp.games.development.programming.algorithms:41 Em 30-07-2012 11:52, Mok-Kong Shen escreveu: > > For playing cards there are riffle shuffling etc. With computers > one is not dependent on constraints resulting from manual working > and consequently could specify more complex operations that may be > rather inconvenient to be performed manually. I like thus to pose > a general question as follows: > > Given a list of n different elements, could one find a shuffling > (permutation) operation on them which can be characterized by the > numerical value of one single parameter (corresponding essentially > to the cutting point of a card deck into two parts in manual > shuffling) and which is likely to lead to the highest degree of > derangement (disorder) of the original list? > > I have done some small amount of experiments but I don't think > to have yet found a really optimal permutation operation. > > Thanks in advance. > > M. K. Shen Pokerstars is an online poker room. They offer a webpage explaining the shuffling algorithm they use: "To perform an actual shuffle, we use another simple and reliable algorithm: - first we draw a random card from the original deck (1 of 52) and place it in a new deck - now original deck contains 51 cards and the new deck contains 1 card - then we draw another random card from the original deck (1 of 51) and place it on top of the new deck - now original deck contains 50 cards and the new deck contains 2 cards - we repeat the process until all cards have moved from the original deck to the new deck This algorithm does not suffer from "Bad Distribution Of Shuffles" described in [1]." It's actually pretty simple and effective, given a good random number generator (they also explain how they generate numbers using entropy generated by the users). If you're interested check out their webpage explaining it: http://www.pokerstars.com/poker/room/features/security/