Thread: Fibonacci with matrixes and recursive powers

m[][]=AlgoritmiMatrici.identita(2);-->it generates the 2x2 identity matrix
AlgoritmiMatrici.prodotto(m,m);-->is the result of the multiplication between m and m

This code should calculate the umteenth number of Fabionacci series, but it alwyas returns 1.

Can anyone help me?

public static int matrice1(int n)
  {
  	int m[][]=AlgoritmiMatrici.identita(2);
 
  	potenzamatrice(m, n-1);
 
  	return m[0][0];
  }
  public static void potenzamatrice(int[][] m, int n)
  {
    	if(n>1)
	{
		potenzamatrice(m, n/2);
		m=AlgoritmiMatrici.prodotto(m,m);
	}	
	if(n%2==1)
	{
		int a[][]={{1,1},{1,0}};
		m=AlgoritmiMatrici.prodotto(m,a);
	}
 }

The array passed to one of the functions is being recreated and the caller expects the change to take effect on the passed object, which does not happen in java. Take the following as an example:

	public static void main(String[] args){
		int[] m = new int[10];
		for ( int i = 0; i < 10; i++ ){
			m[i] = -1;
		}
 
		test(m);
		System.out.println(m[0]);
	}
 
	public static void test(int[] m){
		int v[] = new int[10];
		for ( int i = 0; i < m.length; i++ ){
			v[i] = 1;
		}
		m = v;
	}

Will print -1

Ok.
I tried to return the value of the matrix after the product, but the result is always the same...