From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#32605: [w64] (random) never returns negative Date: Sat, 14 Aug 2021 08:54:53 +0300 Message-ID: <83sfzcbmfm.fsf@gnu.org> References: <855zzpf86u.fsf@gmail.com> <87zhx1ktp0.fsf@gmx.net> <87zhwwhp9i.fsf@gmail.com> <87mtpmls3p.fsf_-_@gnus.org> <83o8a2dbjo.fsf@gnu.org> <86bl62s8qm.fsf@gmail.com> <83czqhdfhm.fsf@gnu.org> <861r6xoxqa.fsf@gmail.com> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="20969"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 32605@debbugs.gnu.org To: Andy Moreton Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sat Aug 14 07:56:10 2021 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 1mEmeQ-0005HQ-9D for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 14 Aug 2021 07:56:10 +0200 Original-Received: from localhost ([::1]:53634 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mEmeO-00048w-Fp for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 14 Aug 2021 01:56:08 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:60724) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mEmeI-00048n-Q4 for bug-gnu-emacs@gnu.org; Sat, 14 Aug 2021 01:56:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:60109) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mEmeI-0005Di-JU for bug-gnu-emacs@gnu.org; Sat, 14 Aug 2021 01:56:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1mEmeI-0001em-GA for bug-gnu-emacs@gnu.org; Sat, 14 Aug 2021 01:56:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 14 Aug 2021 05:56:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 32605 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: confirmed Original-Received: via spool by 32605-submit@debbugs.gnu.org id=B32605.16289205246322 (code B ref 32605); Sat, 14 Aug 2021 05:56:02 +0000 Original-Received: (at 32605) by debbugs.gnu.org; 14 Aug 2021 05:55:24 +0000 Original-Received: from localhost ([127.0.0.1]:43422 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1mEmdg-0001du-Kd for submit@debbugs.gnu.org; Sat, 14 Aug 2021 01:55:24 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:44270) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1mEmdc-0001df-GB for 32605@debbugs.gnu.org; Sat, 14 Aug 2021 01:55:22 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:42746) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mEmdX-0004bH-7p; Sat, 14 Aug 2021 01:55:15 -0400 Original-Received: from 84.94.185.95.cable.012.net.il ([84.94.185.95]:1893 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mEmdN-0001xL-KU; Sat, 14 Aug 2021 01:55:15 -0400 In-Reply-To: <861r6xoxqa.fsf@gmail.com> (message from Andy Moreton on Fri, 13 Aug 2021 22:12:29 +0100) 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:211802 Archived-At: > From: Andy Moreton > Date: Fri, 13 Aug 2021 22:12:29 +0100 > > You elided the detail of my previous message: Because I had nothing useful to say in response. If someone wants to work on a better emulation of 'random' for w64, that's fine; I don't consider myself an expert in this area, and therefore not sure I even understand the significance of providing 31 bits of randomness from a functions such as 'random', which AFAIR is not the standard of RNGs. My goal was to make the current implementation better with relatively simple and straightforward changes. Calling rand_as183 one more time is IMHO not a good solution; but again, I'm not an expert. > > What about the variant below, does it produce better results? > > > > int val = ((rand_as183 () << 15) | rand_as183 ()); > > #ifdef __x86_64__ > > return 2 * val - 0x7FFFFFFF; > > #else > > return val; > > #endif > > Why is this any better ? On 32bit builds it does not return 31 random > bits (only a 30bit value) and on 64bit builds the lowest bit is not > random. I hoped it will be better because it produced negative values as well, not only positive values, without any performance penalty. For a problem that was left unsolved for 3 years it sounds good enough to me. So my proposal is to install the above until someone comes up with a better solution. But if that's unacceptable, let alone if my participation in this discussion is an annoyance, like it seems to be, I'll readily bow out of it.