@Override public double calculate_K(int[] x_index,double[] x_att,int[] y_index,double[] y_att){
  return Math.sqrt((norm2(x_index,x_att,y_index,y_att) / sigma) + (shift * shift));
}

@ Override public double calculate_K ( int [ ] x_index , double [ ] x_att , int [ ] y_index , double [ ] y_att ) { return Math . sqrt ( ( norm2 ( x_index , x_att , y_index , y_att ) / sigma ) + ( shift * shift ) ) ; }
calculates kernel value of vectors x and y .
