[SystemSafety] Difference between software reliability and astrology

[Peter Bishop]

Just for information, we did some code verification on an industrial real-time product (with a real-time operating system) and the majority of faults that mattered were concurrency bugs.

And the trigger for lot of these were a combination of internal state conditions (and, in some cases, external hardware failure).

So not deterministic  in the usual sense of having repeatable failure for a given test - because there are additional variables that cannot be controlled.

Peter Bishop
Adelard
________________________________
From: systemsafety <systemsafety-bounces at lists.techfak.uni-bielefeld.de> on behalf of Derek M Jones <derek at knosof.co.uk>
Sent: 13 August 2024 15:54
To: systemsafety at lists.techfak.uni-bielefeld.de <systemsafety at lists.techfak.uni-bielefeld.de>
Subject: Re: [SystemSafety] Difference between software reliability and astrology

Paul,

>  From previous discussions here and elsewhere (and prior consideration of ISO26262) I was under the impression that
> software is 'generally recognised' to be (ideally) deterministic?

Yes, ideally deterministic, not actually deterministic,
but still practically deterministic for many tasks.

Background radiation (e.g., cosmic rays) is likely to flip
1-bit in 4G os memory every 33 hours
https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fshape-of-code.com%2F2013%2F12%2F13%2Funreliable-cpus-and-memory-the-end-result-of-moores-law%2F&data=05%7C02%7Cpeter.bishop%40nccgroup.com%7C029edab1baaa486e4b9608dcbba7dca4%7Ca41111be486b45f68bd0ee01a62f368e%7C0%7C0%7C638591576838648330%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=OtO6yZcCod3nsPriAw0b3YBUONpdD05q%2B2MSQW8HyzY%3D&reserved=0<https://shape-of-code.com/2013/12/13/unreliable-cpus-and-memory-the-end-result-of-moores-law/>

--
Derek M. Jones           Evidence-based software engineering
blog:https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fshape-of-code.com%2F&data=05%7C02%7Cpeter.bishop%40nccgroup.com%7C029edab1baaa486e4b9608dcbba7dca4%7Ca41111be486b45f68bd0ee01a62f368e%7C0%7C0%7C638591576838658335%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=ZhGGkM8YWp8PF1mPEhpfXigYewfTpYvZe%2F98g6Ip4Jw%3D&reserved=0

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