From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,54889de51045a215 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-10-20 10:53:24 PST Path: archiver1.google.com!news2.google.com!news.maxwell.syr.edu!newsfeed.mathworks.com!wn13feed!wn11feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi.com!rwcrnsc51.ops.asp.att.net.POSTED!not-for-mail Message-ID: <3F9420F7.1020105@comcast.net> From: "Robert I. Eachus" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: += in ada References: <3F7316F7.219F@mail.ru> <17cd177c.0310010606.52da88f3@posting.google.com> <3F8BC74F.2CFBFF37@0.0> <1066312000.671303@master.nyc.kbcfp.com> <1066322883.139702@master.nyc.kbcfp.com> <3F8F372D.9040801@comcast.net> <3F8F4559.50306@noplace.com> <3F92BB1A.202@comcast.net> <3F937C9E.4070403@comcast.net> <1066654259.402836@master.nyc.kbcfp.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 24.34.139.183 X-Complaints-To: abuse@comcast.net X-Trace: rwcrnsc51.ops.asp.att.net 1066672404 24.34.139.183 (Mon, 20 Oct 2003 17:53:24 GMT) NNTP-Posting-Date: Mon, 20 Oct 2003 17:53:24 GMT Organization: Comcast Online Date: Mon, 20 Oct 2003 17:53:24 GMT Xref: archiver1.google.com comp.lang.ada:1216 Date: 2003-10-20T17:53:24+00:00 List-Id: Hyman Rosen wrote: > I was simply pointing out that here was a real-life Ada software > project that devoted plenty of energy to counting cycles, rather > than leaving it to the compiler. And my point was that they didn't. They reused the code from the Ariane 4 without change, assuming that way they didn't have to repeat the cycle counting. After all the same code on the same hardware would produce exactly the same results. Of course, the problem was that the guidance hardware was identical, but the trajectory, inertial moments for the stack, and maximum safe engine deflection were not. That made all of their software reuse assumptions invalid. The next two Ariane 5 failures were hardware failures, but the root cause was identical. You can't change part of the system, and then assume that the requirements don't change elsewhere. (The most recent failure flight 157 in December 2002 dumped two satellites in the Atlantic Ocean. Preliminary data indicated a cooling problem in the uprated Vulcan 2 engines, but a final report has yet to be published.) -- Robert I. Eachus "Quality is the Buddha. Quality is scientific reality. Quality is the goal of Art. It remains to work these concepts into a practical, down-to-earth context, and for this there is nothing more practical or down-to-earth than what I have been talking about all along...the repair of an old motorcycle." -- from Zen and the Art of Motorcycle Maintenance by Robert Pirsig