From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Speeding up (format "%s" STRING) Date: Wed, 27 Sep 2017 13:13:51 -0700 Organization: UCLA Computer Science Department Message-ID: <16bcf8f3-62b7-b98e-5ac0-d6133fe2cf1d@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1506543272 23666 195.159.176.226 (27 Sep 2017 20:14:32 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 27 Sep 2017 20:14:32 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 To: Emacs development discussions Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Sep 27 22:14:27 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dxIiw-0005ds-2c for ged-emacs-devel@m.gmane.org; Wed, 27 Sep 2017 22:14:26 +0200 Original-Received: from localhost ([::1]:56203 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dxIj3-0003Ld-7L for ged-emacs-devel@m.gmane.org; Wed, 27 Sep 2017 16:14:33 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:52627) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dxIiT-0003LN-G0 for emacs-devel@gnu.org; Wed, 27 Sep 2017 16:13:58 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dxIiQ-0007Ry-AV for emacs-devel@gnu.org; Wed, 27 Sep 2017 16:13:57 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:46894) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dxIiQ-0007RL-3L for emacs-devel@gnu.org; Wed, 27 Sep 2017 16:13:54 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id C0926160D98 for ; Wed, 27 Sep 2017 13:13:52 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 0kan4tr-qnSw for ; Wed, 27 Sep 2017 13:13:52 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 17A2A160E31 for ; Wed, 27 Sep 2017 13:13:52 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id uHthwFam_fwC for ; Wed, 27 Sep 2017 13:13:52 -0700 (PDT) Original-Received: from Penguin.CS.UCLA.EDU (Penguin.CS.UCLA.EDU [131.179.64.200]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id F2C85160D98 for ; Wed, 27 Sep 2017 13:13:51 -0700 (PDT) Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 131.179.128.68 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:218833 Archived-At: In Bug#28625 I propose changing the documentation for the 'format' function so that it no longer states that 'format' returns a newly-allocated string. This statement is already incorrect for cases like (format "%s" ""), and removing the statement lets us improve the performance for other cases such as (format "foo") and (format "%s" "foo"). Although I doubt whether any code depends on 'format' always returning a newly-allocated string for these cases, the proposed patch does change the semantics of 'format' slightly, so I'm sending this heads-up to emacs-devel to ask if anyone sees problems with it. As noted in Bug#28625, on my old desktop (AMD Phenom II X4 910e), the proposed patch speeds up (format "%s" "Hello, world!") by a factor of about 9. It also causes Emacs to use less RAM (harder to measure) and simplifies the Emacs source code.