From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Fri Jan 18 08:00:37 2013 Return-Path: X-Original-To: sc22wg5-dom8 Delivered-To: sc22wg5-dom8@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id EDC27356CAC; Fri, 18 Jan 2013 08:00:36 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from nag-j.co.jp (nag-j.co.jp [111.68.142.10]) by www.open-std.org (Postfix) with ESMTP id 3B62B356CA6 for ; Fri, 18 Jan 2013 08:00:34 +0100 (CET) Received: from Maru6 (218-42-159-105.cust.bit-drive.ne.jp [218.42.159.105]) (authenticated bits=0) by nag-j.co.jp (8.14.5/8.14.5) with ESMTP id r0I51te5063310 for ; Fri, 18 Jan 2013 05:02:00 GMT (envelope-from malcolm@nag-j.co.jp) Message-ID: From: "Malcolm Cohen" To: "WG5" References: <20130108205438.50F4E356B56@www.open-std.org><20130113210632.B1C67356BEA@www.open-std.org><20130116050422.92E30356BE0@www.open-std.org><20130116191114.A6A75356A2B@www.open-std.org> In-Reply-To: Subject: Re: (j3.2006) (SC22WG5.4899) [ukfortran] Comment on a comment on the WG5 letterballot on N1947 Date: Fri, 18 Jan 2013 14:01:56 +0900 Organization: =?utf-8?B?5pel5pysTkFH?= MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3555.308 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3555.308 Sender: owner-sc22wg5@open-std.org Precedence: bulk Keith Bierman wrote: >OpenVMS, as far as I know, has only run on processors which physical support >for overflow detection (Alpha, VAX). So this is not a very useful proof point >for the significant number of processors that do not have such hardware >support. The vast majority of processors, including the x86 family, have such hardware support. >> 2. Detection of integer overflow conditions was part of John Reid's >> ENABLE block >>proposal in 1994. > >John was proposing a language feature; > he didn't have the burden of actually implementing it, > so again this example >proves nothing germane to Bill's objections. John's ENABLE block was not shot down by people raising objections to integer overflow detection. >Look at current GPU architecture manuals and hardware specifications for >examples of compute engines for which such handling could prove quite costly >(indeed, making moving computation off the CPU possibly pointless). GPUs are >similar (in many ways) to the old FPS style array processors and Cray style >vector machines (just not nearly as polished or easy to program). > >I'm not saying that these aren't useful or interesting language features. But >those without any "skin the game" w.r.t. >implementing either the hardware or >software should not blithely ignore the costs proposed. (1) No-one is blithely ignoring anything. (2) I do in fact know what it costs in hardware and software; in hardware the costs are not zero but they are miniscule compared to many other cute features that are being implemented. (3) I have in fact implemented it in software without using the hardware support. Or the snarkier but more amusing: "Losing a rocket on the launch pad: a few billion dollars. Being able to brag about your GPU: priceless." Cheers, -- ................................Malcolm Cohen, Nihon NAG, Tokyo.