[SystemSafety] What do we know about software reliability?

[SPRIGGS, John J]

The reliability will be impacted by the fact that this code segment would not compile as written.

From: systemsafety <systemsafety-bounces at lists.techfak.uni-bielefeld.de> On Behalf Of Hugues Bonnin
Sent: 16 September 2020 07:11
To: Derek M Jones <derek at knosof.co.uk>
Cc: systemsafety at lists.techfak.uni-bielefeld.de
Subject: Re: [SystemSafety] What do we know about software reliability?

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<mailto: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/<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<mailto:ladkin at causalis.com>>
>>> À: systemsafety at lists.techfak.uni-bielefeld.de<mailto: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<http://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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