From: "robin" <robin51@dodo.com.au>
Subject: Re: How would Ariane 5 have behaved if overflow checking were not turned off?
Date: Sat, 19 Mar 2011 08:13:10 +1100
Date: 2011-03-19T08:13:10+11:00 [thread overview]
Message-ID: <4d8475d4$0$43834$c30e37c6@exi-reader.telstra.net> (raw)
In-Reply-To: 8ueh3mF3rgU1@mid.individual.net
Niklas Holsti wrote in message <8ueh3mF3rgU1@mid.individual.net>...
>robin wrote:
>> Simon Wright wrote in message ...
>>> "robin" <robin51@dodo.com.au> writes:
>>>
>>>> But only if the error was hardware, which it wasn't.
>>> No, and it wasn't bloody software either!!!
>>
>> I'm afraid that it was (software).
>> Consider this: If just ONE unprotected overflow occurs,
>> the mission is lost.
>
>No. If the unprotected overflow occurs because of a hardware fault or
>noise in one computer only, the mission continues with the other computer.
If there is a problem with one computer,
the mission continues with the other computer, as you say.
However, if an unprotected overflow occurs at any of those 3 unprotected
conversions from float to integer, the mission is doomed.
>> Not a SINGLE unprotected conversion should have been included.
>
>You are being rather dogmatic about this, Robin...
Justifiably so, because it's a real time system.
One programming mistake is all it takes.
>>> it was SYSTEM DESIGN!!! and
>>> no amount of faffing about at the edges of software will ever fix that.
>>
>> The fact remains that in that real-time system,
>> unprotected conversions were included.
>
>After analysis of their possible causes and effects. In the Ariane 4.
>
>> No-one experienced in real-time programming
>> would have permitted those unprotected conversions.
>
>Do you claim to know that the Ariane 4 software developers were
>inexperienced?
Inexperienced in programming real time systems.
>The designers analysed the situation, decided what the software should
>do in case of overflow at this point, and built the software
>accordingly. When the overflow happened in the Ariane 501 launch the
>software did exactly what the designers had decided it should do in this
>case.
Not really; They overlooked what would happen if overflow occurred.
>The argument about what the software should have done instead can be
>endless, and perhaps useful for developing other programs, but does not
>make the Ariane 4 software incorrect.
A bug is something that goes wrong when you don't expect or plan for it.
>The ESA report makes several recommendations to increase robustness, for
>example to activate only those software functions that are needed in
>each phase of a mission. The Ariane 5 designers instead followed the
>KISS principle "if it isn't broken, don't fix it".
The software contained a bug. Just because it didn't fail in Ariane 4
doesn't mean there's not a bug.
> Unfortunately
>"broken" is relative and depends on the environment. The software wasn't
>broken for the Ariane 4, but was broken for the Ariane 5.
I claim that it was broken for both.
For real-time software, it was buggy for the Ariane 4.
next prev parent reply other threads:[~2011-03-18 21:13 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 15:49 How would Ariane 5 have behaved if overflow checking were not turned off? Elias Salomão Helou Neto
2011-03-14 16:17 ` KK6GM
2011-03-14 19:25 ` Yannick Duchêne (Hibou57)
2011-03-14 19:28 ` Vinzent Hoefler
2011-03-14 20:28 ` KK6GM
2011-03-15 4:02 ` Yannick Duchêne (Hibou57)
2011-03-15 4:53 ` Shark8
2011-03-14 18:29 ` Vinzent Hoefler
2011-03-16 10:41 ` How would Ariane 5 have behaved if overflow checking were notturned off? robin
2011-03-16 15:16 ` Simon Wright
2011-03-17 11:48 ` robin
2011-03-16 16:58 ` Martin Krischik
2011-03-16 23:39 ` How would Ariane 5 have behaved if overflow checking werenotturned off? robin
2011-03-17 18:48 ` Vinzent Hoefler
2011-03-18 12:06 ` Alex R. Mosteo
2011-03-18 21:15 ` How would Ariane 5 have behaved if overflow checking were not turned off? robin
2011-03-20 10:42 ` Vinzent Hoefler
2011-03-20 17:06 ` How would Ariane 5 have behaved if overflow checking werenotturned off? Martin Krischik
2011-03-20 17:11 ` Martin Krischik
2011-03-20 18:10 ` Dmitry A. Kazakov
2011-03-21 13:24 ` Leif Roar Moldskred
2011-03-20 13:07 ` How would Ariane 5 have behaved if overflow checking were notturned off? Florian Weimer
2011-03-20 17:00 ` Martin Krischik
2011-03-20 20:17 ` Florian Weimer
2011-03-20 20:37 ` Vinzent Hoefler
2011-03-20 20:14 ` Vinzent Hoefler
2011-03-16 18:20 ` Vinzent Hoefler
2011-03-16 18:29 ` Hyman Rosen
2011-03-16 18:55 ` Vinzent Hoefler
2011-03-16 19:40 ` KK6GM
2011-03-16 20:52 ` Hyman Rosen
2011-03-16 21:02 ` KK6GM
2011-03-16 21:09 ` Shark8
2011-03-16 21:13 ` Hyman Rosen
2011-03-16 21:35 ` Shark8
2011-03-16 22:27 ` Vinzent Hoefler
2011-03-16 21:04 ` Shark8
2011-03-16 21:10 ` Hyman Rosen
2011-03-16 21:27 ` KK6GM
2011-03-16 21:31 ` Shark8
2011-03-16 22:32 ` Vinzent Hoefler
2011-03-18 21:14 ` How would Ariane 5 have behaved if overflow checking were not turned off? robin
2011-03-16 23:46 ` How would Ariane 5 have behaved if overflow checking werenotturned off? robin
2011-03-17 0:26 ` Simon Wright
2011-03-17 11:01 ` Georg Bauhaus
2011-03-17 11:04 ` robin
2011-03-17 13:36 ` Niklas Holsti
2011-03-18 21:13 ` robin [this message]
2011-03-19 10:12 ` How would Ariane 5 have behaved if overflow checking were not turned off? Niklas Holsti
2011-03-17 22:51 ` How would Ariane 5 have behaved if overflow checking werenotturned off? Vinzent Hoefler
2011-03-18 21:13 ` How would Ariane 5 have behaved if overflow checking were not turned off? robin
2011-03-20 10:42 ` Vinzent Hoefler
2011-03-15 6:28 ` Stephen Leake
2011-03-15 17:32 ` Keith Thompson
2011-03-15 17:40 ` KK6GM
2011-03-15 19:44 ` Robert A Duff
2011-03-15 19:12 ` Florian Weimer
2011-03-15 19:45 ` KK6GM
2011-03-15 19:57 ` Vinzent Hoefler
2011-03-20 13:00 ` Florian Weimer
2011-03-20 20:13 ` Vinzent Hoefler
2011-03-15 19:42 ` John B. Matthews
2011-03-17 11:44 ` robin
2011-03-17 18:37 ` Vinzent Hoefler
2011-03-17 23:04 ` How would Ariane 5 have behaved if overflow checking were notturned off? robin
2011-03-18 15:55 ` Vinzent Hoefler
2011-03-17 21:37 ` How would Ariane 5 have behaved if overflow checking were not turned off? Vinzent Hoefler
2011-03-16 10:33 ` robin
2011-03-16 15:08 ` Simon Wright
2011-03-17 12:39 ` robin
2011-03-17 13:41 ` Georg Bauhaus
2011-03-17 23:34 ` How would Ariane 5 have behaved if overflow checking were notturned off? robin
2011-03-18 12:57 ` Hyman Rosen
2011-03-18 16:49 ` KK6GM
2011-03-18 17:18 ` Dmitry A. Kazakov
2011-03-19 17:55 ` Keith Thompson
2011-03-20 18:39 ` Robert A Duff
2011-03-17 18:43 ` How would Ariane 5 have behaved if overflow checking were not turned off? Vinzent Hoefler
2011-03-17 20:58 ` Simon Wright
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