[SystemSafety] What do we know about software reliability?

[Hugues Bonnin]

Derek,

You do not mention cause of software unreliability, but of the hardware which executes it.
My question is on software reliability.

Regards

Hugues 



> Le 16 sept. 2020 à 03:05, Derek M Jones <derek at knosof.co.uk> a écrit :
> 
> Hugues
>> if A then
>>   do_nothing
>> else
>>   fail --potentially hurt and kill people
>> end if
>> end
>> The specification of the software is to do nothing;
>> NB: I'm not asking if it is the best implementation, whatever the criteria are, but just : "is it reliable?"
> 
> The "if A then"
> could be unreliable, in that a cosmic ray could flip its value.
> 
> There are research compilers that reduce the likelihood of a
> cosmic ray altering the behavior of a program:
> http://shape-of-code.coding-guidelines.com/2011/11/07/compiling-to-reduce-the-impact-of-soft-errors-on-program-output/
> 
> Circa 2011, 1-bit of a 4GB RAM had its value flipped roughly every 33
> hours as a result of a cosmic ray hitting the upper atmosphere.
> 
>> regards,
>> Hugues
>> ----- Mail original -----
>>> De: "Peter Bernard Ladkin" <ladkin at causalis.com>
>>> À: systemsafety at lists.techfak.uni-bielefeld.de
>>> Envoyé: Mardi 15 Septembre 2020 19:58:45
>>> Objet: Re: [SystemSafety] What do we know about software reliability?
>>> 
>>> Bev and I and Dewi have a colleague who poses the following question.
>>> 
>>> "We have clients who have installed hundreds of [examples of our kit]
>>> over the last ten years, and
>>> have never seen any failure. They want to use it in further systems
>>> that they build. What arguments
>>> do we/they need to provide in order validly to justify such further
>>> use?"
>>> 
>>> So, what is the answer to that question?
>>> 
>>> PBL
>>> 
>>> Prof. Peter Bernard Ladkin, Bielefeld, Germany
>>> Styelfy Bleibgsnd
>>> Tel+msg +49 (0)521 880 7319  www.rvs-bi.de
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
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> 
> -- 
> Derek M. Jones           Evidence-based software engineering
> tel: +44 (0)1252 520667  blog:shape-of-code.coding-guidelines.com
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