Re: Mars Rover Not Responding

From: Nick Maclaren (nmm1_at_cus.cam.ac.uk)
Date: 01/31/04 

Date: 31 Jan 2004 13:33:28 GMT

In article <I4ySb.22620$Lr6.1991717975@twister2.starband.net>,
Stanley Krute <Stan@StanKrute.com> wrote:
>Howdy Edward
>
>> I am almost flabbergasted into textlessness. The fact that a system
>> ... any system, not just a computer ... may work correctly in some one
>> or two delta range yet fail in some 10 or 20 delta range ... some
>> newbie tyro university graduate wet behind the ears neophyte kid might
>> make this mistake in a small project, and the old seasoned pro salt
>> seen it all manager would take this as a teaching opportunity. But in
>> an entire organization, a huge project putting a robot on a distant
>> planet, and not once did this occur to anybody!?
>
>Yep, you nailed it.
>
>My 5-word software testing book: Run 'er Hard & Long

Sigh. That is very likely the CAUSE of the problem :-(

Any particular test schedule (artificial or natural) will create a
distribution of circumstances over the space of all that are handled
differently by the program. And, remember, we are talking about a
space of cardinality 10^(10^4) to 10^(10^8). Any particular, broken
logic (usually a combination of sections of code and data) may be
invoked only once ever millennium, or perhaps never.

Now, change the test schedule in an apparently trivial way, or use
the program for real, and that broken logic may be invoked once a
day. Ouch. Incidentally, another way of looking at this is the
probability of distinguishing two finite element automata by feeding
in test strings and comparing the results. It was studied some
decades back, and the conclusions are not pretty.

The modern, unsystematic approach to testing is hopeless as an
egnineering technique, though fine as a political or marketing one.
For high-reliability codes, we need to go back to the approaches
used in the days when most computer people were also mathematicians,
engineers or both.

Regards,
Nick Maclaren.

Relevant Pages

  • Re: Mars Rover Not Responding
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  • Re: Mars Rover Not Responding
    ... >> newbie tyro university graduate wet behind the ears neophyte kid might ... Now, change the test schedule in an apparently trivial way, or use ... For high-reliability codes, we need to go back to the approaches ...
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  • Re: Mars Rover Not Responding
    ... >> newbie tyro university graduate wet behind the ears neophyte kid might ... Now, change the test schedule in an apparently trivial way, or use ... For high-reliability codes, we need to go back to the approaches ...
    (comp.lang.java.programmer)
  • Re: Mars Rover Not Responding
    ... >> newbie tyro university graduate wet behind the ears neophyte kid might ... Now, change the test schedule in an apparently trivial way, or use ... For high-reliability codes, we need to go back to the approaches ...
    (comp.theory)