It's a binary search in a 64-bit search space. Powers of two are no more inefficient than other answers, on average, if you assume the answers are uniformly dis

It's a binary search in a 64-bit search space. Powers of two are no more inefficient than other answers, on average, if you assume the answers are uniformly distributed. You could do an exponential search, which is a reasonable choice and makes logical sense, but the exponential search won't be any faster on average.