Class TensorLayout

dnn/include/megdnn/basic_types.h:129–407

* \brief Describing the tensor shape with its actual layout in memory and dtype * * x(i, j, ...) is stored at offset * stride[0]*i + stride[1]*j + ..., in number of elements; physical offset needs * to be multiplied by dtype size. */

 * to be multiplied by dtype size.
 */
struct TensorLayout : public TensorShape {
    /*!
     * \brief Describes min and max offsets of tensor elements with respect to
     *      its first element, so all tensor elements are guaranteed to be in
     *      the range [elem[0]+low, elem[0]+last). Besides, we have a high to
     *      describe the range including row pitch when using image2D
     */
    struct Span {
        ptrdiff_t low_elem, low_byte;
        size_t high_elem, high_byte;
        //! The differece between high_elem and last elem is that last_elem describes
        //! the last element of a tensor regardless of the row pitch at the last row. It
        //! will be useful when copying into a part of image.
        size_t last_elem, last_byte;

        Span(ptrdiff_t low_elem, ptrdiff_t low_byte, size_t high_elem, size_t high_byte,
             size_t last_elem, size_t last_byte)
                : low_elem(low_elem),
                  low_byte(low_byte),
                  high_elem(high_elem),
                  high_byte(high_byte),
                  last_elem(last_elem),
                  last_byte(last_byte) {}
        size_t dist_elem() const { return high_elem - low_elem; }

        size_t dist_byte() const { return high_byte - low_byte; }

        size_t dist_last_byte() const { return last_byte - low_byte; }
    };

    /*!
     * \brief Describing the requirements for tensor layouts
     *
     * Some runtime (e.g. opencl) may have alignment requirements for special
     * memory types (e.g. image in texture memory). Format objects can be used
     * to impose such constraints on methods related to tensor strides.
     *
     * Note that ImplBase is defined in tensor_format.h
     */
    class Format {
    public:
        class ImplBase;

#if MEGDNN_CC_HOST
        MGE_WIN_DECLSPEC_FUC Format();
        MGE_WIN_DECLSPEC_FUC Format(DType dtype);

        const ImplBase* impl() const { return m_impl; }

        enum class Type;

        //! get impl type; defined in tensor_format.h
        inline Type type() const;

        //! convert to the implementation class; exception would be raised if
        //! type mismatches
        template <class Impl>
        const Impl& as_impl() const {