CRNLazyDistanceMatrix.h

Go to the documentation of this file.

/* Copyright 2015 Université Paris Descartes
 * 
 * This file is part of libcrn.
 * 
 * libcrn is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * libcrn 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 Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with libcrn.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * file: CRNLazyDistanceMatrix.h
 * \author Yann LEYDIER
 */

#ifndef CRNLazyDistanceMatrix_HEADER
#define CRNLazyDistanceMatrix_HEADER

#include <CRNMath/CRNSquareMatrixDouble.h>
#include <vector>

namespace crn
{
    template<typename DATA, typename DISTANCE> class LazyDistanceMatrix
    {
        public:
            LazyDistanceMatrix(const std::vector<DATA> &d, DISTANCE &&dist):
                data(d), 
                distance(std::forward<DISTANCE>(dist)),
                distmat(d.size()),
                cache(d.size(), std::vector<bool>(d.size(), false))
            { }
            LazyDistanceMatrix(const LazyDistanceMatrix&) = default;
            LazyDistanceMatrix(LazyDistanceMatrix&&) = default;
            LazyDistanceMatrix& operator=(const LazyDistanceMatrix&) = delete;
            LazyDistanceMatrix& operator=(LazyDistanceMatrix&&) = delete;

            inline size_t GetRows() const noexcept { return data.size(); }

            inline size_t GetCols() const noexcept { return data.size(); }

            inline double At(size_t i, size_t j)
            {
                if (!cache[i][j])
                {
                    distmat[i][j] = distmat[j][i] = distance(data[i], data[j]);
                    cache[i][j] = cache[j][i] = true;
                }
                return distmat[i][j];
            }

            const SquareMatrixDouble& GetDistanceMatrix()
            {
                for (size_t i = 0; i < data.size(); ++i)
                    for (size_t j = i + 1; j < data.size(); ++j)
                        if (!cache[i][j])
                            At(i, j);
                return distmat;
            }

        private:
            SquareMatrixDouble distmat;
            const std::vector<DATA> &data;
            DISTANCE distance;
            std::vector<std::vector<bool>> cache;
    };

    template<typename DATA, typename DISTANCE> inline LazyDistanceMatrix<DATA, DISTANCE> MakeLazyDistanceMatrix(const std::vector<DATA> &d, DISTANCE &&dist) { return LazyDistanceMatrix<DATA, DISTANCE>{d, std::forward<DISTANCE>(dist)}; }
}

#endif