From mboxrd@z Thu Jan  1 00:00:00 1970
Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail
From: Eli Zaretskii <eliz@gnu.org>
Newsgroups: gmane.emacs.devel
Subject: Re: Which is faster: narrow-to-region or delete-region?
Date: Wed, 22 Sep 2021 08:51:04 +0300
Message-ID: <83wnn9w43b.fsf@gnu.org>
References: <AM9PR09MB49771FFB125823ED820AF13596A19@AM9PR09MB4977.eurprd09.prod.outlook.com>
Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214";
	logging-data="383"; mail-complaints-to="usenet@ciao.gmane.io"
Cc: emacs-devel@gnu.org
To: Arthur Miller <arthur.miller@live.com>
Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Wed Sep 22 07:51:53 2021
Return-path: <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>
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 <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>)
	id 1mSvAf-000ATe-LS
	for ged-emacs-devel@m.gmane-mx.org; Wed, 22 Sep 2021 07:51:53 +0200
Original-Received: from localhost ([::1]:33482 helo=lists1p.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.90_1)
	(envelope-from <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>)
	id 1mSvAe-0006ZJ-91
	for ged-emacs-devel@m.gmane-mx.org; Wed, 22 Sep 2021 01:51:52 -0400
Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:49814)
 by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <eliz@gnu.org>) id 1mSvA1-0005tJ-FX
 for emacs-devel@gnu.org; Wed, 22 Sep 2021 01:51:13 -0400
Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:52878)
 by eggs.gnu.org with esmtp (Exim 4.90_1)
 (envelope-from <eliz@gnu.org>)
 id 1mSv9z-0004CP-A4; Wed, 22 Sep 2021 01:51:12 -0400
Original-Received: from 84.94.185.95.cable.012.net.il ([84.94.185.95]:2579
 helo=home-c4e4a596f7)
 by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <eliz@gnu.org>)
 id 1mSv9y-0007hX-JB; Wed, 22 Sep 2021 01:51:11 -0400
In-Reply-To: <AM9PR09MB49771FFB125823ED820AF13596A19@AM9PR09MB4977.eurprd09.prod.outlook.com>
 (message from Arthur Miller on Tue, 21 Sep 2021 22:10:09 +0200)
X-BeenThere: emacs-devel@gnu.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: "Emacs development discussions." <emacs-devel.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/emacs-devel>,
 <mailto:emacs-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/emacs-devel>
List-Post: <mailto:emacs-devel@gnu.org>
List-Help: <mailto:emacs-devel-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/emacs-devel>,
 <mailto:emacs-devel-request@gnu.org?subject=subscribe>
Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org
Original-Sender: "Emacs-devel"
 <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>
Xref: news.gmane.io gmane.emacs.devel:275288
Archived-At: <http://permalink.gmane.org/gmane.emacs.devel/275288>

> From: Arthur Miller <arthur.miller@live.com>
> Date: Tue, 21 Sep 2021 22:10:09 +0200
> 
> 
> I have a DEFUN in the middle of a temporary buffer; which is faster to use to
> eliminate the rest of the code from the calculations for font lock:
> 
> (narrow-to-region defun-begin defun-end)
> 
> or
> 
> (delete-region (point-min) defun-begin) +
> (delete-region defun-end (point-max))

The narrow-to-region method must be much faster, since it only sets a
bunch of variables and does little else.  Moreover, it cannot trigger
GC, whereas delete-region method very well can.

> I have tried both and notice no differences.

Maybe in a very small buffer.