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Why Computers Suck At Math
antdude writes "This TechRadar article explains why computers suck at math, and how simple calculations can be a matter of life and death, like in the case of a Patriot defense system failing to take down a Scud missile attack: 'The calculation of where to look for confirmation of an incoming missile requires knowledge of the system time, which is stored as the number of 0.1-second ticks since the system was started up. Unfortunately, 0.1 seconds cannot be expressed accurately as a binary number, so when it's shoehorned into a 24-bit register — as used in the Patriot system — it's out by a tiny amount. But all these tiny amounts add up. At the time of the missile attack, the system had been running for about 100 hours, or 3,600,000 ticks to be more specific. Multiplying this count by the tiny error led to a total error of 0.3433 seconds, during which time the Scud missile would cover 687m. The radar looked in the wrong place to receive a confirmation and saw no target. Accordingly no missile was launched to intercept the incoming Scud — and 28 people paid with their lives.'"
Disclosure: I am a programmer.
I had a conjecture that the Patriot missile was a Raytheon project. Not a particularly well-based speculation, but I did the RFA for confirmation. For some reason, they did not mention the manufacturer. They felt free to mention Intel and Google, but I guess the manufacturer was an advertiser.
As it happens, 40 years ago I was an end user of a Raytheon air-defense missile system called the Hawk. There was a common derogatory phrase about Raytheon. I guess we might call it a meme now.
It was cute and perhaps relevant to this article, but it has been so long, I can not reproduce it.
Anyway, whoever manufactured the Patriot, I sort of doubt that the first cause was a bad programmer.
A war story. This is not all Raytheon's fault, but it makes a nice slander.
At Kassel, there was a NSA antenna farm with a hawk battery next to it. It was noteworthy, but not unusual, for Migs to buzz the antenna farm. I guess it happened every few months. Go figure.