/*CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C     IMPLEMENTATION OF THE EXTENDED ORACLE PENALTY FUNCTION
C     ------------------------------------------------------
C
C     Input arguments:
C     ----------------
C     f           Objective function value
C     res         Residual function value
C     omega       Oracle parameter
C     acc         Accuracy for constraint violation 
C
C     Output arguments:
C     -----------------
C     p           Penalty function value
C
C     ------------------------------------------------------
C
C     Reference:
C
C     Schlueter M., Gerdts M.: "The oracle penalty method",
C     Journal of Global Optimization (Springer), 
C     Vol. 47, Issue 2, Page 293-325, 2010.
C
C     ------------------------------------------------------
C
C     Author (C) :   Dr. Martin Schlueter
C                    Information Initiative Center (IIC),
C                    Division of Large Scale Computing Systems,
C                    Hokkaido University, JAPAN.
C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC*/

#include<math.h>

double oracle_penalty( double f, double res, double omega, double acc) 
{
	double p;
    double alpha;

	if(f <= omega && res <= acc)
	{
	  p = f - omega;
	}
	else
	{
	  if(f <= omega)
	  {	  
		  p = res;
	  }
	  else
	  { 
		  if(res < (f-omega)/3.0)
		  {	      
			  alpha = ((f-omega) * 0.80754991-res) / (f-omega-res);	        
		  }	      

		  if(res >= (f-omega)/3.0 && res <= (f-omega))
		  {	       
			  alpha = 1.0 - 0.5 / sqrt((f-omega)/res);	          
		  }
	      
		  if(res > (f-omega))
		  {	      
			  alpha = 0.5 * sqrt((f-omega)/res);	          
		  }
	  
		  p = alpha * (f-omega) + (1.0-alpha) * res;	      
	  }
	}

	return p;
}