Search a sorted array by narrowing possible locations to progressively smaller intervals. Begin with two Fibonacci numbers, p (F(n)) and q (F(n+1)), such that p < n ≤ q, where n is the size of the array. The first step checks location p. The size of the next interval is p, if the key is less than the item at that location, or q-p (F(n-1)) if it is greater.