This is a optimization to prevent redundant calculations. If it was not performed the result would be the same, just served slightly slower.
The whitepaper you linked is a great one, I was all over it a few years back when we built our first models. It should be recommended reading for anyone interested in CS.
The whitepaper you linked is a great one, I was all over it a few years back when we built our first models. It should be recommended reading for anyone interested in CS.