From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.devel Subject: Re: Add seq-shuffle Date: Tue, 17 Sep 2024 06:09:09 +0200 Message-ID: <87ed5iq5ui.fsf@dataswamp.org> References: <87msk8p4mb.fsf@dataswamp.org> <14bc4905-38b4-459d-8522-7cc33bbadd18@alphapapa.net> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="24148"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: emacs-devel@gnu.org Cancel-Lock: sha1:VuN7bSKYn3S+w9Plv96P48AVg6s= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Sep 17 12:59:39 2024 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1sqVvm-000677-Pm for ged-emacs-devel@m.gmane-mx.org; Tue, 17 Sep 2024 12:59:38 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sqVv1-0000bz-PN; Tue, 17 Sep 2024 06:58:52 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sqPWj-0004Fm-Rt for emacs-devel@gnu.org; Tue, 17 Sep 2024 00:09:22 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sqPWh-0002Ne-Nl for emacs-devel@gnu.org; Tue, 17 Sep 2024 00:09:21 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1sqPWf-0000iV-I5 for emacs-devel@gnu.org; Tue, 17 Sep 2024 06:09:17 +0200 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: emacs-devel@gnu.org Mail-Copies-To: never Received-SPF: pass client-ip=116.202.254.214; envelope-from=ged-emacs-devel@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Tue, 17 Sep 2024 06:58:50 -0400 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:323689 Archived-At: Adam Porter wrote: > That's a neat and concise solution. Pretty! > It seems to produce a decently random For better random, https://dataswamp.org/~incal/emacs-init/random-urandom/ > sorting, but I'd guess that it may not perform well for > large sequences. For example: > > (let (comparisons) > (list :result (seq-sort (lambda (a b) > (push (cons a b) comparisons) > (zerop (random 2))) > (number-sequence 0 10)) > :num-comparisons (length comparisons))) > ;; (:result (6 0 9 1 5 10 8 2 7 3 4) :num-comparisons 26) > > In testing that expression repeatedly, I see that the number > of comparisons varies between about 23 and 26. Okay, but is that bad? Isn't that linear plus logarithmic i.e. linear? But I actually didn't know it varied, I thought it always tested all, wouldn't that be the arithmetic sum, so for 11 items 1 + ... + 10 = 55 tests? (defun arith-sum (n) (cl-loop with sum = 0 for i from 1 to (1- n) do (cl-incf sum i) finally return sum) ) ;; (arith-sum 11) ; 55 How long are long lists? Not 11 items, if we are talking marshalling, maybe you want to get a CS algorithm book and see what specific algorithms they have for the purpose that scale the best for huge sets? If linear is too slow, you want logarithmic. -- underground experts united https://dataswamp.org/~incal