I remember being surprised when Intel released a Pentium chip that couldn't do f... | Hacker News

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		JoeAltmaier on Feb 10, 2023 \| parent \| context \| favorite \| on: There Are Only Four Billion Floats–So Test Them Al... I remember being surprised when Intel released a Pentium chip that couldn't do floating point right. It would have been trivial to, I don't know, try dividing by 10 and then multiplying back and checking the answer. It couldn't do that. At the time I was thinking, their test group could have tested every single mantissa over several operations exhaustively. Why didn't they? What excuse could they have had? It was a computer; they feel no pain when asked to do laborious repetitive tasks.

dragontamer on Feb 11, 2023 [–]

You'd think so, except no. Floating point operations are innately lossy and even non-associative, and non communative.

A+B+C does not equal B+C+A in floating point.

JoeAltmaier on Feb 12, 2023 | [–]

Which should happen in entirely predictable and orderly fashion. In fact, they should be testing for that too.

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