I think about the time my manager dismissed an interviewee as not understanding map-reduce because he couldn’t solve some problem in 2 passes, but rather needed

I think about the time my manager dismissed an interviewee as not understanding map-reduce because he couldn’t solve some problem in 2 passes, but rather needed 3. I asked him to explain how to do it in 2. And he was like, “what? It’s easy!” Then another person on the team who over heard it also asked. Eventually the whole team was there, asking him to prove it, and he spent over an half an hour trying to explain it, and none of us were getting it. The consensus from everyone (except the manager) that it was an unfair question that relied on a a very subtle assumption about the data that wasn’t obvious at all, and that 3 passes was the minimum required Without the that assumption. Of course the manager said everyone was stupid and it was a good question. That manager remains my counter example of what a good manager is.