From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#41544: 26.3; Possible incorrect results from color-distance Date: Wed, 03 Jun 2020 17:24:56 +0300 Message-ID: <83blm0cjlz.fsf@gnu.org> References: <5C4A633D-8222-4439-BE37-9B8674F1DA6D@acm.org> <87r1v2aat3.fsf@tromey.com> <9902865C-01B4-4E50-A433-DBC8B8311234@acm.org> <83tuzueogo.fsf@gnu.org> <6272275C-560C-4437-90F1-2A8294D27019@acm.org> <83o8q2elja.fsf@gnu.org> <83mu5mel4o.fsf@gnu.org> <77F1DDD3-A69F-40ED-902D-74986D5E6596@acm.org> <83y2p5cumz.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="72133"; mail-complaints-to="usenet@ciao.gmane.io" Cc: tom@tromey.com, simon@polaris64.net, 41544@debbugs.gnu.org To: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Wed Jun 03 16:26:12 2020 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1jgULM-000IcO-Nu for geb-bug-gnu-emacs@m.gmane-mx.org; Wed, 03 Jun 2020 16:26:12 +0200 Original-Received: from localhost ([::1]:55084 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgULL-0003Xd-Ov for geb-bug-gnu-emacs@m.gmane-mx.org; Wed, 03 Jun 2020 10:26:11 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:60584) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgULC-0003WJ-Gl for bug-gnu-emacs@gnu.org; Wed, 03 Jun 2020 10:26:03 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:60991) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jgULC-0003NB-80 for bug-gnu-emacs@gnu.org; Wed, 03 Jun 2020 10:26:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1jgULC-0007XQ-2u for bug-gnu-emacs@gnu.org; Wed, 03 Jun 2020 10:26:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Wed, 03 Jun 2020 14:26:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 41544 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: patch Original-Received: via spool by 41544-submit@debbugs.gnu.org id=B41544.159119432228924 (code B ref 41544); Wed, 03 Jun 2020 14:26:02 +0000 Original-Received: (at 41544) by debbugs.gnu.org; 3 Jun 2020 14:25:22 +0000 Original-Received: from localhost ([127.0.0.1]:44304 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jgUKX-0007WS-OT for submit@debbugs.gnu.org; Wed, 03 Jun 2020 10:25:21 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:47660) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jgUKW-0007WE-88 for 41544@debbugs.gnu.org; Wed, 03 Jun 2020 10:25:20 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:42299) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgUKQ-00037i-5L; Wed, 03 Jun 2020 10:25:14 -0400 Original-Received: from [176.228.60.248] (port=2586 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1jgUKO-0004wq-LX; Wed, 03 Jun 2020 10:25:13 -0400 In-Reply-To: (message from Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= on Tue, 2 Jun 2020 22:41:03 +0200) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:181458 Archived-At: > From: Mattias Engdegård > Date: Tue, 2 Jun 2020 22:41:03 +0200 > Cc: tom@tromey.com, simon@polaris64.net, 41544@debbugs.gnu.org > > > I'd prefer to fix only the symmetry bug (which AFAIU happens because > > we use bit shifts on signed integers), without introducing any other > > effects on the function's behavior and return values. AFAIU, such a > > fix should not require any changes outside of the function itself. > > Very well, it is obviously an improvement. The reason for the current asymmetry was actually that the algorithm discarded the low bits; what about fixing that as well? Sure, let's make it as accurate as the return value allows. > The improved accuracy amounts to less than 1 % of difference in the return value; no other code needs changing, and we get the symmetry for free. Proposed patch attached. Not sure I understand completely: does this patch make the function symmetric? If so, what additional improvements did you have in mind when you mentioned more fixing above? Thanks.