Optimizing Fibonacci
The first optimization we are going to perform eliminates a method call, as shown in Listing 1–3. As this implementation is recursive, removing a single call in the method dramatically reduces the total number of calls. For example, computeRecursively(30) generated 2,692,537 calls while computeRecursivelyWithLoop(30) generated “only” 1,346,269. However, the performance of this method is still not acceptable considering the response-time criteria defined above, 100 milliseconds or less, as computeRecursivelyWithLoop(30) takes about 270 milliseconds to complete.
Listing 1–3. Optimized Recursive Implementation of Fibonacci Series
public class Fibonacci {
public static long computeRecursivelyWithLoop (int n)
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