From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Improving regexp-opt Date: Fri, 12 Apr 2019 12:53:06 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="174060"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Apr 12 18:54:08 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hEzRG-000j8a-28 for ged-emacs-devel@m.gmane.org; Fri, 12 Apr 2019 18:54:06 +0200 Original-Received: from localhost ([127.0.0.1]:40011 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hEzRE-0008Nz-Uq for ged-emacs-devel@m.gmane.org; Fri, 12 Apr 2019 12:54:04 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:53860) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hEzQR-0008MS-DP for emacs-devel@gnu.org; Fri, 12 Apr 2019 12:53:16 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hEzQQ-0003m6-Iy for emacs-devel@gnu.org; Fri, 12 Apr 2019 12:53:15 -0400 Original-Received: from [195.159.176.226] (port=35292 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hEzQQ-0003kr-8C for emacs-devel@gnu.org; Fri, 12 Apr 2019 12:53:14 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.89) (envelope-from ) id 1hEzQO-000i5G-Jr for emacs-devel@gnu.org; Fri, 12 Apr 2019 18:53:12 +0200 X-Injected-Via-Gmane: http://gmane.org/ Cancel-Lock: sha1:I3ZNVhFNzoTLc4vEDXYnVZnzWjM= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 195.159.176.226 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:235353 Archived-At: > The pros: > If the resulting strings "came from" a regexp that is splittable, the > FA implementation always simplifies to it. In pratice, these are > uncommun, and in most cases, the results are equivalent. > > The cons: > The algorithm for FA seams to have greater computation complexity, > takes about 20 times to compute in average. Furthermore, even when the result is noticeably shorter, have you compared the performance of the regexp-matcher? I expect that you won't be able to see a measurable difference there. IOW it's just not a good deal. As I said, if you really want to improve on regexp-opt, you have to go through a *real* DFA and that means not returning a regexp but a DFA, so it's a completely different beast from `regexp-opt`. Stefan