3 ms·

I didn't quite get why the error in the absolute time would cause the effect. Sure using 0.1 seconds as a unit is problematic because 0.1 can't be represented a

I didn't quite get why the error in the absolute time would cause the effect. Sure using 0.1 seconds as a unit is problematic because 0.1 can't be represented accurately in binary, but I didn't see how the tracking error was relative to the absolute time. This short article by Skeel[1] cleared it up, where he notes that the real issue was rather that they had changed the way they converted the absolute time to floating-point, but had missed a spot so the code mixed new and old floating-point times. [1]: https://www-users.cse.umn.edu/~arnold/disasters/Patriot-dharan-skeel-siam.pdf https://www-users.cse.umn.edu/~arnold/disasters/Patriot-dhar...

lifthrasiir 3y ago
Oh well, that's even worse. If I understood correctly, that means there are two timestamps t1 and t2 from each radar pulse, which difference in seconds is computed as `f(t1) - g(t2)` where g somehow truncated to 24 bits instead of the full 48 bits. I don't exactly get why f and g are different enough to cause the truncation, it might well be that f and g are correct but the final subtraction missed lower bits of `f(t1)` instead.
ahazred8ta 3y ago
In the 1980s the Vancouver Stock Exchange silently lost 500 points due to rounding errors - repeated addition of small numbers. They didn't notice for two years. https://en.m.wikipedia.org/wiki/Vancouver_Stock_Exchange#Rounding_errors_on_its_Index_price https://en.m.wikipedia.org/wiki/Vancouver_Stock_Exchange#Rou...