Complete Program

When Fib(N) is computed recursively, very many activations are created and destroyed. Sometimes the time it takes to compute Fib(N) is used as a benchmark, a program that tests the speed of a computer. Here is a bare-minimum program for Fib(N):

class FibonacciCalc
{
  public int Fib( int N )
  {
    if       ( N==1 ) 
      return 1;
    else if  ( N==2 ) 
      return 1;
    else
      return Fib( N-1 ) + Fib( N-2 );
  }
}

class FibonacciTester
{
  public static void main ( String[] args)
  {
    int argument = Integer.parseInt( args[0] );
    
    FibonacciCalc f = new FibonacciCalc();
    int result = f.Fib( argument );
    System.out.println("Fib(" + argument + ") is " + result );
  }
}

Here are some results of running the program on my IBM ThinkPad 380ED. You might wish to run the program on your computer and compare speeds.

N	10	20	30	35	40	45
Fib(N)	55	6765	832040	9227465	102334155	1134903170
time (sec)	2	2	3	4	30	360

It takes a few seconds for the Java system to load and start running. This time is included in these measurements.