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.'"

Comments

Re:"User error"?

[Hurricane78]

Yep. That was a epic fail.

The rule is: If a user *can* do something wrong, he *will*!

How can they not know that?

Re:Patriot success rate was likely extremely infla

[Philip K Dickhead]

Look. When the system is named "Patriot", you already have enough information to understand the framing context - if you care to have the particular insight. This is a propaganda tool, like the rockets launched from Airstrip One.

It fulfilled its mission when it was designed, manufactured and labeled as "The Patriot Missile System". Ballistic interception is a secondary mission and fulfillment is unnecessary for success.