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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 101deb,885dab3998d28a4 X-Google-Attributes: gid101deb,public X-Google-Thread: f74ae,eca28648989efca9 X-Google-Attributes: gidf74ae,public X-Google-Thread: 103376,885dab3998d28a4 X-Google-Attributes: gid103376,public X-Google-Thread: 107079,eca28648989efca9 X-Google-Attributes: gid107079,public From: wayne@cs.toronto.edu (Wayne Hayes) Subject: Re: Ariane 5 failure Date: 1996/09/27 Message-ID: <1996Sep27.023246.18774@jarvis.cs.toronto.edu>#1/1 X-Deja-AN: 185597344 distribution: inet x-nntp-posting-host: qew.cs.toronto.edu references: <52bm1c$gvn@rational.rational.com> <1780E8471.KUNNE@frcpn11.in2p3.fr> organization: CS Lab, University of Toronto newsgroups: sci.astro,comp.lang.ada,sci.math.num-analysis,comp.lang.pl1 Date: 1996-09-27T00:00:00+00:00 List-Id: In article , Matthew Heaney wrote: >Why, yes. If the rocket blows up, at the cost of millions of dollars, then >I'm not clear what the value of "faster execution" is. The rocket's gone, >so what difference does it make how fast the code executed? If you left >the range checks in, your code would be *marginally* slower, but you'd >still have your rocket, now wouldn't you? You have a moot point. In this case, catching the error wouldn't have helped. The out-of-bounds error happened in a piece of code designed for the Ariane-4, in which it was *physically impossible* for the value to overflow (the Ariane-4 didn't go that fast, and it was a velocity variable). Then the code was used, as-is, in the Ariane-5, without an analysis of how the code would react in the new hardware, which flew faster. Had the analysis been done, they wouldn't have added bounds checking, they would have modified the code to actually *work*, because they would have realized that the code was *guaranteed* to fail on the first flight. -- "And a woman needs a man... || Wayne Hayes, wayne@cs.utoronto.ca like a fish needs a bicycle..." || Astrophysics & Computer Science -- U2 (apparently quoting Gloria Steinem?) || http://www.cs.utoronto.ca/~wayne