BruteForceIterator.hh

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///
/// @file  BruteForceIterator.hh
/// @brief Generic tensor indexing iterator
///

//**** This file is a part of the HAMMER library
//**** Copyright (C) 2016 - 2020 The HAMMER Collaboration
//**** HAMMER is licensed under version 3 of the GPL; see COPYING for details
//**** Please note the MCnet academic guidelines; see GUIDELINES for details

// -*- C++ -*-
#ifndef HAMMER_MATH_MULTIDIM_BRUTEFORCEITERATOR
#define HAMMER_MATH_MULTIDIM_BRUTEFORCEITERATOR

#include "Hammer/Math/MultiDimensional.fhh"
#include "Hammer/Math/MultiDim/AlignedIndexing.hh"

namespace Hammer {


    namespace MultiDimensional {

        class BruteForceIterator {
        public:
            BruteForceIterator();
            BruteForceIterator(IndexList dimensions, IndexList fixed = {});

            BruteForceIterator(const BruteForceIterator&) = default;
            BruteForceIterator(BruteForceIterator&&) = default;
            BruteForceIterator& operator=(const BruteForceIterator&) = default;
            BruteForceIterator& operator=(BruteForceIterator&&) = default;

            ~BruteForceIterator() = default;

        public:

            BruteForceIterator begin() const;

            BruteForceIterator end() const;

            BruteForceIterator& operator++();

            BruteForceIterator operator++(int n);

            IndexList operator*();

            bool isSame(const BruteForceIterator& other) const;

        private:
            void incrementEntry(size_t position, int n);
            void setInitialState();

            IndexList _dimensions;
            IndexList _fixedMask;      ///< the strides for each tensor index (necessary to convert coordinates to position in `_data`)
            IndexList _state;

        };


        inline bool operator==(const BruteForceIterator& lhs,
                               const BruteForceIterator& rhs) {
            return lhs.isSame(rhs);
        }

        inline bool operator!=(const BruteForceIterator& lhs, const BruteForceIterator& rhs) {
            return !(lhs == rhs);
        }

    }

} // namespace Hammer

namespace std {

    template<>
    struct iterator_traits<Hammer::MultiDimensional::BruteForceIterator> {
        using difference_type = ptrdiff_t;
        using value_type = Hammer::IndexList;
        using pointer = Hammer::IndexList*;
        using reference = Hammer::IndexList&;
        using iterator_category = forward_iterator_tag;
    };

}

#endif