/**
 * Copyright (c) 2008, 2009, 2010 Regents of the University of California
 * 
 * ADModelbuilder and associated libraries and documentations are
 * provided under the general terms of the "BSD" license.
 * 
 * License:
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * 2.  Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * 3.  Neither the name of the  University of California, Otter Research,
 * nor the ADMB Foundation nor the names of its contributors may be used
 * to endorse or promote products derived from this software without
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 */

//file: hem_func.cpp
#include <fvar.hpp>
void hemholtz_energy(int n, dmatrix A, dvector b, dvar_vector x, double& f)
{
  double R=.00005;
  double T=290;
  double root2=pow(2.,.5);
  dvariable btx = b*x;  
  dvariable log_one_minus_btx = log(1-btx);
  dvariable z = R * T * ( x * (log(x)-log_one_minus_btx) );     
  z -= (x * A * x)/(2*root2*btx) * log( (1+(1+root2)*btx)/(1+(1-root2)*btx) );
  f=value(z);
}
