Re: [SystemSafety] Software reliability (or whatever you would prefer to call it)

From: David Haworth < >
Date: Tue, 10 Mar 2015 12:41:39 +0100


Hi Yiannis,

> (... no Heisenberg please ... if quantum mechanics introduced any
> real randomness in the world as we know it, we would be in real trouble
> :)

I hate to destroy your comfortable illusion, but a long time ago (in a galaxy quite close to where you live) the ERNIE machine that decided who won the weekly and monthly premium bond draw in the UK used the random noise in a particular kind of diode as the source for the random numbers. I believe the noise is a quantum effect.

https://en.wikipedia.org/wiki/Premium_Bond#ERNIE https://en.wikipedia.org/wiki/Hardware_random_number_generator

I also spent many "happy" hours analysing why a range of radiation monitors produced by the company I then worked for reported that they had failed occasionally. The answer was that the tiny scrap of radioactive material that was built into the Geiger tube in the equipment, that was intended to provide at least one measurable decay event every 3 seconds or so would in reality sometimes not produce anything for 10 seconds or more. What's more, the calculations that we made and the simulations that we ran correlated with the observed phenomenon remarkably accurately.

So in some sense, the randomness introduced by quantum mechanics had a direct effect on my own experience. And quite likely on all those who have won prizes in the premium bond draw :-)

Dave

On 2015-03-10 10:37:33 +0000, Yiannis I Papadopoulos wrote:
> " Software essentially boils down to a string of one's and nought's.
> Given the same inputs (and that always comes from the chaotic
> environment) then the output will always be the same. It therefore
> makes no sense to talk about 'software reliability' "
>
>
> The premise is true but does the conclusion follow?
>
>
> Take the example of throwing a dice.
>
>
> If you know everything about the dice and its environment and apply the
> laws of physics you can determine the outcome. You can be god,
> replicate the exact conditions and you will get the same outcome every
> time (... no Heisenberg please ... if quantum mechanics introduced any
> real randomness in the world as we know it, we would be in real trouble
> :)
>
>
> So, what is the purpose then of talking about randomness, probability
> and statistics to describe such phenomena? I think the answer is that
> it is often the best, sometimes the only way, to reason about complex
> deterministic processes. It is done all the time in science, why not in
> software?
>
>
> --
>
> Yiannis Papadopoulos
>
> http://www2.hull.ac.uk/science/computer_science/our_staff/staff_profile
> s/yiannis_papadopoulos.aspx

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-- 
David Haworth B.Sc.(Hons.), OS Kernel Developer    david.haworth_at_xxxxxx
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