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In alt.global-warming Dhu on Gate <campbell@neotext.ca> wrote:
> On Fri, 4 Oct 2024 23:46:20 -0000 (UTC), R Kym Horsell wrote:
> 
>> In alt.global-warming Dhu on Gate <campbell@neotext.ca> wrote:
>>> On Fri, 4 Oct 2024 22:12:30 -0000 (UTC), R Kym Horsell wrote:
>>> 
>>>> In alt.global-warming Alan <nuh-uh@nope.com> wrote:
>>>>> On 2024-10-01 01:40, R Kym Horsell wrote:
>>>>>> In alt.global-warming Dhu on Gate <campbell@neotext.ca> wrote:
>>>>>>> On Sun, 29 Sep 2024 23:19:24 -0500, AlleyCat wrote:
>>>>>>>> Nebraska, USA: Within minutes, a single hailstorm reduced 14,000 solar
>>>>>>>> panels, worth millions of dollars, into a pile of toxic debris-leaching
>>>>>>>> materials like cadmium and lead into the soil.
>>>>>>> Lotta folks don't get how fragile hi-tech shit is.
>>>>>>> Dhu
>>>>>> 
>>>>>> 
>>>>>> Long gone are the days of servicing your own vehicle.
>>>>>> Apart from oiling some bearings you can't and sometimes are
>>>>>> prohibited by law from fixing your own car.
>>>>>> I was helping a neighbor recently and it turned out you
>>>>>> needed to break an old mil grade encryption to even ask it here it hurt.
>>>>>> 
>>>>> 
>>>>> What kind of car was that?
>>>> 
>>>> I pre-answered that. :)
>>>> 
>>>>> All cars built for sale in North America have had a standard OBD-II port 
>>>>> that can be read by various scanners costing anywhere from $20...
>>>>> ...to a lot more depending on complexity.
>>>> 
>>>> There's a theorem of computer science that roughly says
>>> 
>>> That's a "side effect" of completeness vs. consistency.  
>>> 
>>> IF you make a system "complete", that is covering all possible 
>> ...
>> 
>> You're talking to someone that has been doing that stuff for 1/2 a lifetime. :)
>> I like to think of it in terms of self-reference.
>> Any system that has to look at itself will strike problems.
>> Can you make a machine that can diagnose its own faults?
>> What happens when the diagnostic part has a fault?
>> 
>> NASA always had an engineering policy that every mission-critical system
>> had  to have triple redundancy. If not 3 identical systems then
>> at least 3 different  subsystems had to be able to do the same job.
>> But the point of failure generally was the part of the system that
>> took the vote of the 3 identical systems to find out the majority-decision
>> and switch out the subsystem that was wrong.
>> 
>> In MV you often see the central computer start up and ask various sub-systems
>> to run diagnostics. The sub-systems poke some circuits and see if the
>> results are what they expect. If so, they send an OK back to the start-up
>> request from the central processor.
>> 
>> But the checking runs into a problem. If you have to check say 1 million
>> bits to decide if your sub-system is working then how do you check
>> they are all correct? A typical method is to use a hash. Boil the
>> sequence of 1 million correct bits down into a 16 bit number.
>> Take the hash of the million and check it against the 16 bits in PROM.
>> But there is a logical problem. A million bits can have "many" more
>> possible combinations of values than 16 bits. So it means there can
>> be many problems that hash to exactly the "everything is OK" code.
>> 
>> But the hashing idea is cheap and everyone uses it "all the time".
>> 
>> So it's a minor miracle these days when you put your bread in a toaster
>> that it cooks it for a couple mins, the toast pops up, and it's edible.
> 
> This is where the model for the 'net breaks down.  At this point in 
> a real conversation I'd be offerin' to buy you a drink and pump you
> some more ...
> 
> Dhu


If you smiled I'm doing my job.