From owner-sc22wg5@open-std.org Thu Jun 25 10:47:01 2009 Return-Path: X-Original-To: sc22wg5-dom7 Delivered-To: sc22wg5-dom7@www2.open-std.org Received: by www2.open-std.org (Postfix, from userid 521) id 66234C76BBF; Thu, 25 Jun 2009 10:47:01 +0200 (CET DST) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from ppsw-0.csi.cam.ac.uk (ppsw-0.csi.cam.ac.uk [131.111.8.130]) by www2.open-std.org (Postfix) with ESMTP id AD56EC4596C for ; Thu, 25 Jun 2009 10:46:34 +0200 (CET DST) X-Cam-AntiVirus: no malware found X-Cam-SpamDetails: not scanned X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Received: from hermes-2.csi.cam.ac.uk ([131.111.8.54]:40324) by ppsw-0.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.150]:25) with esmtpa (EXTERNAL:nmm1) id 1MJkbI-0002d6-2P (Exim 4.70) for sc22wg5@open-std.org (return-path ); Thu, 25 Jun 2009 09:46:32 +0100 Received: from prayer by hermes-2.csi.cam.ac.uk (hermes.cam.ac.uk) with local (PRAYER:nmm1) id 1MJkbI-0003YL-Ng (Exim 4.67) for sc22wg5@open-std.org (return-path ); Thu, 25 Jun 2009 09:46:32 +0100 Received: from [83.67.89.123] by webmail.hermes.cam.ac.uk with HTTP (Prayer-1.3.1); 25 Jun 2009 09:46:32 +0100 Date: 25 Jun 2009 09:46:32 +0100 From: "N.M. Maclaren" To: sc22wg5 Subject: Re: [ukfortran] (SC22WG5.4031) (j3.2006) LOCK/UNLOCK question Message-ID: In-Reply-To: <20090625060203.E9891C3BB09@www2.open-std.org> References: <4A38A3BB.9090208@nag-j.co.jp><4A38B917.8080202@llnl.gov> <4A391682.8060208@cray.com> <061720091627.18164.4A39196C000C05A4000046F422230703729B0A02D29B9B0EBF02019C050C079D0B020A08D2050C070B@att.net> <4A3930E3.8070505@cray.com> <061720091851.25112.4A393B4100015BA20000621822228869349B0A02D29B9B0EBF02019C050C079D0B020A08D2050C070B@att.net> <4A397E50.9010406@nag-j.co.jp> <4A3F9897.8010103@llnl.gov> <4A3FA25D.1050507@cray.com> <4A3FF921.9070703@llnl.gov> <20090622221248.1FEF4C178E5@www2.open-std.org> <20090623084602.88A3EC178E5@www2.open-std.org> <20090624020300.8EE77C178E5@www2.open-std.org> <20090625033421.31AAEC3BB09@www2.open-std.org> <20090625041351.94A5AC3BB09@www2.open-std.org> <20090625060203.E9891C3BB09@www2.open-std.org> X-Mailer: Prayer v1.3.1 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Sender: owner-sc22wg5@open-std.org Precedence: bulk On Jun 25 2009, Malcolm Cohen wrote: >Bill Long wrote: > >> What I do object to is Nick's frequent declarations that other >> programmers are hopeless and incompetent. > >I am truly surprised that you read his statements about certain things >being extremely difficult - so difficult that even the experts have >trouble with them - as being about other programmers' competency at all. I, too, am truly surprised at that - especially as Van said the same thing, and I pointed out that Hoare (one of THE big names in this area) had come to the same conclusion. Have you read Hoare's rationale for inventing BSP? The reasons that I said that it is error-prone is that it is too easy to write code that has a slightly more complicated temporal structure than you can analyse in your head, and there are essentially NO tools for detecting errors and analysing failures. A few will help with deadlock, but none will help much with complicated livelock, and none will help at all with the common mistake of assuming that A is ordered before B because of dependencies, when there is an unexpected path that isn't ordered. In my experience, most exports discover such errors only when porting their 'working' programs to a new system that has radically different properties than the ones they have used before. So programs that use system-specific communication code or are used on only a few systems often have such bugs lurking in the undergrowth. Regards, Nick Maclaren, University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England. Email: nmm1@cam.ac.uk Tel.: +44 1223 334761 Fax: +44 1223 334679