NonuniformTableLinear.hpp

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/*
  Copyright 2009, 2010, 2011, 2012 SINTEF ICT, Applied Mathematics.
  Copyright 2009, 2010, 2011, 2012 Statoil ASA.

  This file is part of the Open Porous Media project (OPM).

  OPM is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  OPM 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
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef OPM_NONUNIFORMTABLELINEAR_HEADER_INCLUDED
#define OPM_NONUNIFORMTABLELINEAR_HEADER_INCLUDED

#include <cmath>
#include <exception>
#include <vector>
#include <utility>

#include <opm/common/ErrorMacros.hpp>
#include <opm/core/utility/linearInterpolation.hpp>

namespace Opm
{


    template<typename T>
    class NonuniformTableLinear
    {
    public:
        NonuniformTableLinear();

        NonuniformTableLinear(const std::vector<double>& x_values,
                              const std::vector<T>& y_values);

        std::pair<double, double> domain();

        void rescaleDomain(std::pair<double, double> new_domain);

        double operator()(const double x) const;

        double derivative(const double x) const;

        double inverse(const double y) const;

        bool operator==(const NonuniformTableLinear& other) const;

    protected:
        std::vector<double> x_values_;
        std::vector<T> y_values_;
        mutable std::vector<T> x_values_reversed_;
        mutable std::vector<T> y_values_reversed_;
    };


    // A utility function
    template <typename FI>
    bool isNondecreasing(const FI beg, const FI end)
    {
        if (beg == end) return true;
        FI it = beg;
        ++it;
        FI prev = beg;
        for (; it != end; ++it, ++prev) {
            if (*it < *prev) {
                return false;
            }
        }
        return true;
    }



    // Member implementations.

    template<typename T>
    inline
    NonuniformTableLinear<T>
    ::NonuniformTableLinear()
    {
    }

    template<typename T>
    inline
    NonuniformTableLinear<T>
    ::NonuniformTableLinear(const std::vector<double>& x_values,
                            const std::vector<T>& y_values)
        : x_values_(x_values), y_values_(y_values)
    {
        assert(isNondecreasing(x_values.begin(), x_values.end()));
    }

    template<typename T>
    inline std::pair<double, double>
    NonuniformTableLinear<T>
    ::domain()
    {
        return std::make_pair(x_values_[0], x_values_.back());
    }

    template<typename T>
    inline void
    NonuniformTableLinear<T>
    ::rescaleDomain(std::pair<double, double> new_domain)
    {
        const double a = x_values_[0];
        const double b = x_values_.back();
        const double c = new_domain.first;
        const double d = new_domain.second;
        // x in [a, b] -> x in [c, d]
        for (int i = 0; i < int(x_values_.size()); ++i) {
            x_values_[i] = (x_values_[i] - a)*(d - c)/(b - a) + c;
        }
    }

    template<typename T>
    inline double
    NonuniformTableLinear<T>
    ::operator()(const double x) const
    {
        return Opm::linearInterpolation(x_values_, y_values_, x);
    }

    template<typename T>
    inline double
    NonuniformTableLinear<T>
    ::derivative(const double x) const
    {
        return Opm::linearInterpolationDerivative(x_values_, y_values_, x);
    }

    template<typename T>
    inline double
    NonuniformTableLinear<T>
    ::inverse(const double y) const
    {
        if (y_values_.front() < y_values_.back()) {
            return Opm::linearInterpolation(y_values_, x_values_, y);
        } else {
            if (y_values_reversed_.empty()) {
                y_values_reversed_ = y_values_;
                std::reverse(y_values_reversed_.begin(), y_values_reversed_.end());
                assert(isNondecreasing(y_values_reversed_.begin(), y_values_reversed_.end()));
                x_values_reversed_ = x_values_;
                std::reverse(x_values_reversed_.begin(), x_values_reversed_.end());
            }
            return Opm::linearInterpolation(y_values_reversed_, x_values_reversed_, y);
        }
    }

    template<typename T>
    inline bool
    NonuniformTableLinear<T>
    ::operator==(const NonuniformTableLinear<T>& other) const
    {
        return x_values_ == other.x_values_
            && y_values_ == other.y_values_;
    }

} // namespace Opm

#endif // OPM_NONUNIFORMTABLELINEAR_HEADER_INCLUDED