From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from minnie.tuhs.org (minnie.tuhs.org [45.79.103.53]) by inbox.vuxu.org (OpenSMTPD) with ESMTP id bd3639b9 for ; Sat, 19 Oct 2019 21:23:57 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 8702593E46; Sun, 20 Oct 2019 07:23:56 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id CD5B493D6E; Sun, 20 Oct 2019 07:23:36 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id D4E5593D6E; Sun, 20 Oct 2019 07:23:33 +1000 (AEST) X-Greylist: delayed 505 seconds by postgrey-1.36 at minnie.tuhs.org; Sun, 20 Oct 2019 07:23:32 AEST Received: from pio-pvt-msa2.bahnhof.se (pio-pvt-msa2.bahnhof.se [79.136.2.41]) by minnie.tuhs.org (Postfix) with ESMTPS id 72D8F93D31 for ; Sun, 20 Oct 2019 07:23:32 +1000 (AEST) Received: from localhost (localhost [127.0.0.1]) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTP id 3649E3F374 for ; Sat, 19 Oct 2019 23:15:06 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from pio-pvt-msa2.bahnhof.se ([127.0.0.1]) by localhost (pio-pvt-msa2.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MOlFiXWUZBH6 for ; Sat, 19 Oct 2019 23:15:05 +0200 (CEST) Received: from localhost (unknown [85.24.253.59]) (Authenticated sender: mc469656) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTPA id 0E5063F32B for ; Sat, 19 Oct 2019 23:15:05 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by localhost (Postfix) with ESMTPS id B55382E02CC for ; Sat, 19 Oct 2019 23:15:04 +0200 (CEST) Date: Sat, 19 Oct 2019 21:15:03 +0000 From: Michael =?utf-8?B?S2rDtnJsaW5n?= To: tuhs@minnie.tuhs.org Message-ID: References: <201910191440.x9JEe8PB035921@tahoe.cs.Dartmouth.EDU> <443935c0-b033-e3ae-ea63-6a0fb3f8eb9e@kilonet.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <443935c0-b033-e3ae-ea63-6a0fb3f8eb9e@kilonet.net> Subject: Re: [TUHS] How to do differential/integral on a PDP-7, was: Space Travel X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" On 19 Oct 2019 16:40 -0400, from krewat@kilonet.net (Arthur Krewat): > Not to mention, if you start using log/alog tables, and/or sin/cos/tan > tables, and interpolation, you can quickly ramp up computation speed for > simple games that have a small matrix of coordinates. Indeed; like I said, at some point, it becomes just a matter of how quickly you need the answer. It's not really _difficult_ to do any of this if you're willing to wait a while to learn the value of 1/2. It's a little more involved if you want log10(e^pi * pi^e) _fast_. After all, Apollo navigated to, around, and back from, the Moon, using an on-board computer that today would barely run that thermostat that someone mentioned. 2048 15+1-bit word RAM (3840 bytes, plus parity), 36864 15+1-bit word ROM (69120 bytes, again plus parity). It could display three general-purpose five-digit decimal numbers, each with sign, plus three specific-purpose two-digit decimal numbers, and was operated using a 19-key keyboard (0-9, plus, minus, and a few function keys). In fairness, a lot of the heavier calculations were performed by Mission Control on the ground and the results were uplinked either digitally or via voice transmission to the spacecraft, but still... Those programmers didn't exactly have the luxury of, when they realized they were running out of memory, just sending along the rest of the software on tape and telling the user to load it on an as-needed basis. Premature optimization is the root of all evil in 99% of the cases, but in that last 1%, a targeted optimization effort is exactly what you need. -- Michael Kjörling • https://michael.kjorling.se • michael@kjorling.se “The most dangerous thought that you can have as a creative person is to think you know what you’re doing.” (Bret Victor)