From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: How to canonicalize a time object Date: Sun, 14 Aug 2022 13:15:27 -0400 Message-ID: References: <877d3ahlxi.fsf@gnus.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="21473"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) Cc: emacs-devel@gnu.org, Paul Eggert To: Lars Ingebrigtsen Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Aug 14 19:16:36 2022 Return-path: 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 ) id 1oNHE4-0005QH-M0 for ged-emacs-devel@m.gmane-mx.org; Sun, 14 Aug 2022 19:16:36 +0200 Original-Received: from localhost ([::1]:48832 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oNHE3-0003TY-EU for ged-emacs-devel@m.gmane-mx.org; Sun, 14 Aug 2022 13:16:35 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:39096) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oNHD6-0002mT-MZ for emacs-devel@gnu.org; Sun, 14 Aug 2022 13:15:37 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:5761) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oNHD4-0001vF-4J for emacs-devel@gnu.org; Sun, 14 Aug 2022 13:15:35 -0400 Original-Received: from pmg2.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id D2CBC8071D; Sun, 14 Aug 2022 13:15:31 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 3BEB080470; Sun, 14 Aug 2022 13:15:30 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1660497330; bh=DayZWOyGUvRPtPKRFpfTMh4d74gQql0jIGnRzzwjciU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=NtTlr/i24BVf4fiG3MBsS44kLzGEsAjhmB7G4wmeYr7Oif25cURrVEVnrKlKdm7bU pXAeeXB8THjPv3FnqJMHyWvFB/ZsVapWnJr2bqyAVSlr4+ztIw9HMvDEA5oZSZYVTp R25cU/tsgpGNxPPPsMCVT6xoi0KYc1enIf6RJ5JjJYfWJouZBeA9mK1I1oI+xfsP35 pQc25hEoE+PRIBr8/jFje5F+tdnPiY2z2KsCU17ejQqNsvGkwNKP0ZUNJvg1kVOLsE NfvOf8g/1xvnSRPpkMdGL2IVHaGyL0uMEN3oWL5aeaW6NI3qpsJNP3Xi4qjpfSTnFS 8/AVdIVq+Se+A== Original-Received: from pastel (unknown [45.72.195.111]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id D58F812049B; Sun, 14 Aug 2022 13:15:29 -0400 (EDT) In-Reply-To: <877d3ahlxi.fsf@gnus.org> (Lars Ingebrigtsen's message of "Sun, 14 Aug 2022 17:41:45 +0200") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:293452 Archived-At: Lars Ingebrigtsen [2022-08-14 17:41:45] wrote: > Stefan Monnier writes: >> What's the best way in ELisp to turn an arbitrary time value into one >> that will be as efficient as possible for `lisp_time_argument`? > I'm not quite sure I understand the question -- the `t' type for > `time-convert' is supposed to be the most efficient representation of an > arbitrary time value, Yes, it seems that using the representation returned by `time-convert` when you ask for the `t` form is the "most efficient" for some definition of it, but I'm specifically interested in the efficiency of passing the result to `lisp_time_argument`: that function uses `lisp_to_timespec` which has various "fast paths" and I'm not sure how to make sure we'll go through them. E.g. if we do (time-convert FLOAT t) the returned value will be of the form (TICKS . 2^51) and for (time-convert (HI LOW US) t) it'll be (TICKS . 10^6), but `lisp_to_timespec` doesn't seem to have a fast path for 2^51 and I'm not sure it has one for 10^6 (nor 10^12 used for (HI LOW US PS)). It appears that the best choice currently is to use `timespec_hz` (or 1 if the time is a whole number of seconds), but: - There doesn't seem to be an easy way to get `timespec_hz` from ELisp. - It's cumbersome to find out if a time value is a whole number of seconds. - It's not very elegant to have ELisp code do such gymnastics which depend on the presence/absence of specific fast-paths in the C code, which my also change in the future. > but if you don't have sub-second resolution to your time, the > `integer' one is probably more efficient? Indeed, tho only for that specific situation :-( Of course, maybe we shouldn't care, and just presume that the slow path which does a GMP mul+div is plenty fast anyway. Stefan