Class DType

dnn/include/megdnn/dtype.h:418–551

! * \brief Information about a data type that can be accessed at runtime */

 * \brief Information about a data type that can be accessed at runtime
 */
class DType {
private:
    MGE_WIN_DECLSPEC_FUC MEGDNN_NORETURN void on_request_lowbit_size() const;
    // HACK: This is required in ParameterizedDType::downcast_from
public:
    MGE_WIN_DECLSPEC_FUC MEGDNN_NORETURN void on_assert_is_failed(
            const char* rname) const;

protected:
    struct Trait {
        const char* const name;
        const uint16_t size_log;  //!< log2 of sizeof(dt) for non-lowbit
        const uint16_t low_bit;   //!< 0 for non-lowbit; otherwise num bits
        DTypeEnum enumv;
        DTypeCategory category;
        DTypeSignedness signedness;
        const bool has_param;
    };
    Trait* m_trait;

    explicit DType(Trait* t) : m_trait(t) {}

public:
    DType() : m_trait(nullptr) {}

    bool valid() const { return m_trait != nullptr; }

    /*!
     * \brief name of this data type
     */
    const char* name() const { return m_trait ? m_trait->name : "invalid"; }

    /*!
     * \brief size of elem_num this data type, if fraction form return ceil
     */
    size_t size(size_t elem_num) const {
        if (m_trait->low_bit != 0)
            return static_cast<size_t>((m_trait->low_bit * elem_num + 7) / 8);
        return elem_num << m_trait->size_log;
    }

    /*!
     * \brief max number of elements within representation
     *
     * The total size of the tensor (in bytes) should not exceed size_t range.
     */
    size_t max_elements() const {
        if (m_trait->low_bit != 0)
            return std::numeric_limits<size_t>::max();

        return std::numeric_limits<size_t>::max() >> m_trait->size_log;
    }

    size_t low_bit() const { return m_trait->low_bit; }

    bool is_low_bit() const { return low_bit() != 0; }

    bool is_complex() const {