If you lay out a carry-lookahead tree the naive way, it occupies a N x logN rectangle with the N-bit adder along the N side, but most of the rectangle is empty

If you lay out a carry-lookahead tree the naive way, it occupies a N x logN rectangle with the N-bit adder along the N side, but most of the rectangle is empty (each layer has half as many gates as the previous). You can easily pack it more densely on a ad hoc basis, but I don't know of a systematic approach, so possibly it's only a (mildly large) constant factor better than the naive way at scale. > Do you have some reference Nope; that's why I was asking for one.