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: Re: Using the GNU GMP Library for Bignums in Emacs Date: Sun, 22 Apr 2018 02:06:11 -0700 Organization: UCLA Computer Science Department Message-ID: References: <29f933ac-a6bf-8742-66a7-0a9d6d3e5a88@disroot.org> <83bmecy6fx.fsf@gnu.org> <0d3175d8-d996-651e-b221-71978bde3a65@cs.ucla.edu> <51e619e0-ee38-eb97-6c1d-0925b675290a@disroot.org> <8e12135a-0fcc-7aa3-d000-731d2f26d918@disroot.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1524387901 26795 195.159.176.226 (22 Apr 2018 09:05:01 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 22 Apr 2018 09:05:01 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 Cc: eliz@gnu.org, emacs-devel@gnu.org To: "Siraphob (Ben) Phipathananunth" , rms@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Apr 22 11:04:57 2018 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 1fAAvZ-0006ql-9V for ged-emacs-devel@m.gmane.org; Sun, 22 Apr 2018 11:04:57 +0200 Original-Received: from localhost ([::1]:40246 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fAAxe-0002hn-9f for ged-emacs-devel@m.gmane.org; Sun, 22 Apr 2018 05:07:06 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:59732) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fAAws-0002h3-JE for emacs-devel@gnu.org; Sun, 22 Apr 2018 05:06:21 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fAAwr-0002E0-PG for emacs-devel@gnu.org; Sun, 22 Apr 2018 05:06:18 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:37644) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fAAwo-0002BF-0E; Sun, 22 Apr 2018 05:06:14 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 423F316005C; Sun, 22 Apr 2018 02:06:12 -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 mo4jbAX0IfDb; Sun, 22 Apr 2018 02:06:11 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 83FEC16133D; Sun, 22 Apr 2018 02:06:11 -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 8HMQDjC2CQpn; Sun, 22 Apr 2018 02:06:11 -0700 (PDT) Original-Received: from [192.168.1.9] (unknown [47.154.30.119]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 5807C16005C; Sun, 22 Apr 2018 02:06:11 -0700 (PDT) In-Reply-To: <8e12135a-0fcc-7aa3-d000-731d2f26d918@disroot.org> 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:224783 Archived-At: Siraphob (Ben) Phipathananunth wrote: > Would it not slow down computation to have to constantly convert > between the two types? A bit perhaps, but it shouldn't be that big a deal. Most integer computat= ion=20 will likely be fixnum only, and the only slowdown there will be integer o= verflow=20 checking that we currently aren't doing. With decent hardware and compile= r, I'd=20 guess this would cost us three machine instructions per Lisp arithmetic=20 operation, including the conditional branch that is typically not taken. = Hardly=20 anybody will notice. > In such a case, a fix could > be to convert lisp numbers exceeding fixnum limits to bignums for the > rest of the number's life (until GC). This ensures memory usage is kept > low for fixnum computations. Yes, the idea is to use bignums to represent numbers outside of fixnum ra= nge,=20 and to use fixnums to represent numbers inside fixnum range. Bignums requ= ire=20 garbage collection; fixnums do not.