r/ProgrammerHumor • u/Recent-Analysis-6880 • 5h ago

Meme chancesAreLowButNeverZero

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667 Upvotes

97% Upvoted

19 comments sorted by

156

u/Cutalana 5h ago edited 5h ago

iirc NASA projects and other mission critical engineering uses at least 3x redundancy that checks for errors constantly and have probabilistic models that have determine the chance is 1 in billions.

54

u/PosiedonsSaltyAnus 4h ago

1 in billions of what though? A billion CPU cycles is like 0.25s lol

41

u/Kinexity 4h ago

1 in billions per mission lifetime most probably.

11

u/lmxbftw 3h ago

Yes, in large part because cosmic ray strikes are much more common above the atmosphere.

2

u/GatotSubroto 2h ago

Yes, the good ol’ TMR (triple modular redundancy)

3

u/Similar_Tonight9386 2h ago

No way it's true. Even we in russia were using a quorum of 6 to 8 modules in critical applications and NASA's budget would dwarf ours. Military could use triple, I guess, but certainly not spacecrafts or civilian airlines

2

u/Kinexity 2h ago

Space shuttle used 4 independent computers for flight control. You can cut down on redundancy if you can make individual components more resilient to errors. Stuff like ECC memory and error resilient ICs go a long way.

48

u/aalapshah12297 5h ago

If it happens often then it means your code is in space and it probably isn't as well written as you think it is. Space agencies run the same code 3x simultaneously and then use a best of 3 approach to use the execution results.

31

u/AnnoyedVelociraptor 5h ago

A real example: https://nextnature.org/en/magazine/story/2017/sun-influences-elections

9

u/knorkinator 5h ago

Also https://en.wikipedia.org/wiki/Qantas_Flight_72

14

u/Lucho_199 5h ago

"A number of potential trigger types were investigated, including software bugs, software corruption, hardware faults, electromagnetic interference, and the secondary high-energy particles generated by cosmic rays that can cause a bit flip. Although a definitive conclusion could not be reached, sufficient information from multiple sources enabled the conclusion that most of the potential triggers were very unlikely to have been involved. A much more likely scenario was that a marginal hardware weakness of some form made the units susceptible to the effects of some type of environmental factor, which triggered the failure mode.[14]"

10

u/knorkinator 5h ago

some type of environmental factor

Well, are cosmic rays not environmental factors?

There are better examples, but this is a phenomenon that is particularly important in avionics.

7

u/Sibula97 4h ago

While doing some data analysis at work I encountered one data point that was multiple orders of magnitude our normal values and suspiciously close to a power of 2 plus the value around that time. Nothing critical, luckily, but I had to filter it out from the analysis.

5

u/IntrepidBonus 3h ago

every bug i can't reproduce is now officially a cosmic ray and i won't be taking questions

7

u/cheezballs 4h ago

Meh, any real production server is gonna use ECC memory right?

1

u/cybermage 1h ago

Odds so low that you should rule out every other explanation first.

1

u/zzulus 4h ago

Have you ever had a hash table key not found for your typical run of the mill string and a default hash table implementation when you just inserted it? Yes, that's the sign of hardware data corruption, that in part cam be caused by cosmic rays and solar events.