interp_helper.h

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 * \file dnn/src/common/cv/interp_helper.h
 *
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#pragma once

#include "src/common/cv/aligned_allocator.h"

#include "megdnn/opr_param_defs.h"

#include <cstdint>
#include <memory>
#include <mutex>

namespace megdnn {
namespace megcv {

using InterpolationMode = megdnn::param::WarpPerspective::InterpolationMode;
using BorderMode = megdnn::param::WarpPerspective::BorderMode;

/*!
 * \brief helper for generating interpolation tables for different interpolation
 *        modes
 */
template <int INTER_BITS_ = 5, int INTER_MAX_ = 7,
          int INTER_REMAP_COEF_BITS_ = 15>
class InterpolationTable {
public:
    using IMode = InterpolationMode;

    static constexpr int INTER_BITS = INTER_BITS_;
    static constexpr int INTER_MAX = INTER_MAX_;
    static constexpr int INTER_REMAP_COEF_BITS = INTER_REMAP_COEF_BITS_;
    static constexpr int INTER_TAB_SIZE = (1 << INTER_BITS);
    static constexpr int INTER_TAB_SIZE2 = INTER_TAB_SIZE * INTER_TAB_SIZE;
    static constexpr int INTER_REMAP_COEF_SCALE = 1 << INTER_REMAP_COEF_BITS;

    /*!
     * \brief get interpolation table
     *
     * The table dimension is [INTER_TAB_SIZE][INTER_TAB_SIZE][ksize][ksize]
     *
     * \param imode interpolation mode
     * \param fixpt if this is true, return a table for int16_t; else return a
     *              table for float
     * \return table for int16 or float according to fixpt
     */
    static const void* get_table(InterpolationMode imode, bool fixpt);
#if MEGDNN_X86
    /**
     * \brief get interpolation table for linear mode.
     *
     * This current only avaiable in \warning X86.
     *
     * \return bilineartab_ic4_buf
     */
    static const int16_t* get_linear_ic4_table();
#endif

private:
    template <int ksize>
    struct Table {
        float ftab[INTER_TAB_SIZE2 * ksize * ksize];
        int16_t itab[INTER_TAB_SIZE2 * ksize * ksize];
#if MEGDNN_X86
        alignas(128) int16_t bilineartab_ic4_buf[INTER_TAB_SIZE2 * 2 * 8];

        static void* operator new(std::size_t sz) {
            return ah::aligned_allocator<Table, 128>().allocate(sz /
                                                                sizeof(Table));
        }
        void operator delete(void* ptr) noexcept {
            ah::aligned_allocator<Table, 128>().deallocate(
                    reinterpret_cast<Table*>(ptr), 0);
        }
#endif
    };

    struct TableHolderBase {
        std::mutex mtx;

        //! get table pointer; return whether already init
        virtual bool get(float**, int16_t**) = 0;

    protected:
        ~TableHolderBase() = default;
    };

    template <int ksize>
    struct TableHolder final : public TableHolderBase {
        std::unique_ptr<Table<ksize>> table;

        bool get(float** ftab, int16_t** itab) override {
            bool ret = true;
            if (!table) {
                ret = false;
                table.reset(new Table<ksize>);
            }
            *ftab = table->ftab;
            *itab = table->itab;
            return ret;
        }
    };

    static void init_inter_tab_1d(InterpolationMode imode, float* tab,
                                  int tabsz);

    static inline void interpolate_linear(float x, float* coeffs);
    static inline void interpolate_cubic(float x, float* coeffs);
    static inline void interpolate_lanczos4(float x, float* coeffs);

    static TableHolder<2> sm_tab_linear;
    static TableHolder<4> sm_tab_cubic;
    static TableHolder<8> sm_tab_lanczos4;
};

}  // namespace megcv
}  // namespace megdnn

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