/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*

 Copyright (C) 2001, 2002, 2003 Nicolas Di Césaré

 This file is part of QuantLib, a free-software/open-source library

 for financial quantitative analysts and developers - http://quantlib.org/

 QuantLib is free software: you can redistribute it and/or modify it

 under the terms of the QuantLib license.  You should have received a

 copy of the license along with this program; if not, please email

 <quantlib-dev@lists.sf.net>. The license is also available online at

 <https://www.quantlib.org/license.shtml>.

 This program is distributed in the hope that it will be useful, but WITHOUT

 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 FOR A PARTICULAR PURPOSE.  See the license for more details.

*/

#include <ql/math/optimization/linesearch.hpp>

#include <ql/math/optimization/problem.hpp>

#include <ql/math/optimization/constraint.hpp>

namespace QuantLib {

    Real LineSearch::update(Array& params,

                            const Array& direction,

                            Real beta,

                            const Constraint& constraint) {

        Real diff=beta;

        Array newParams = params + diff*direction;

        bool valid = constraint.test(newParams);

        Integer icount = 0;

        while (!valid) {

            if (icount > 200)

                QL_FAIL("can't update linesearch");

            diff *= 0.5;

            icount ++;

            newParams = params + diff*direction;

            valid = constraint.test(newParams);

        }

        params += diff*direction;

        return diff;

    }

}