example_01a.hpp

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// @HEADER
// *****************************************************************************
//               Rapid Optimization Library (ROL) Package
//
// Copyright 2014 NTESS and the ROL contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#include "ROL_StdVector.hpp"

using namespace ROL;

template<class Real>
class Zakharov {

    public:

        template<class ScalarT>
        ScalarT value(const Vector<ScalarT> &x, Real &tol );

};



template<class Real>
template<class ScalarT>
ScalarT Zakharov<Real>::value(const Vector<ScalarT>& x, Real &tol) {

      

    ROL::Ptr<const std::vector<ScalarT> > xp = (dynamic_cast<const StdVector<ScalarT>&>(x)).getVector();

    int n = xp->size();

    ScalarT xdotx = 0;
    ScalarT kdotx = 0;
    ScalarT J = 0;
   
    // Compute dot products 
    for(int i=0; i<n; ++i) {
        xdotx += pow((*xp)[i],2);       // (k,x)
        kdotx += Real(i+1)*(*xp)[i];  // (x,x)
    }

    // Sum terms in objective function
    J = xdotx + pow(kdotx,2)/4.0 + pow(kdotx,4)/16.0;
    
    return J;
}