mindspore2022/mindspore/nn/cell.py

# Copyright 2020 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ============================================================================
"""cell"""
import inspect
import time
import gc
import os
from collections import OrderedDict
import numpy
from mindspore import log as logger
from .. import context
from ..common import dtype as mstype
from ..common.api import _executor, _pynative_exec
from .._checkparam import Validator
from ..common.parameter import Parameter, ParameterTuple
from .._c_expression import init_backend, Cell_
from ..ops.primitive import Primitive
from ..ops.operations import HookBackward
from ..ops.functional import cast
from ..parallel._tensor import _load_tensor_by_layout
from ..common.tensor import Tensor


class Cell(Cell_):
    """
    Base class for all neural networks.

    A 'Cell' could be a single neural network cell, such as conv2d, relu, batch_norm, etc. or a composition of
    cells to constructing a network.

    Note:
        In general, the autograd algorithm will automatically generate the implementation of the gradient function,
        but if back-propagation(bprop) method is implemented, the gradient function will be replaced by the bprop.
        The bprop implementation will receive a Tensor `dout` containing the gradient of the loss w.r.t.
        the output, and a Tensor `out` containing the forward result. The bprop needs to compute the
        gradient of the loss w.r.t. the inputs, gradient of the loss w.r.t. Parameter variables are not supported
        currently.

    Args:
        auto_prefix (bool): Recursively generate namespaces. Default: True.

    Examples:
        >>> class MyCell(Cell):
        >>>    def __init__(self):
        >>>        super(MyCell, self).__init__()
        >>>        self.relu = P.ReLU()
        >>>
        >>>    def construct(self, x):
        >>>        return self.relu(x)
    """
    IGNORE_LIST = ['_scope', '_cell_init_args', '_auto_prefix', '_cells', '_params', '_construct_inputs_names',
                   '_construct_inputs_num', '_create_time', '_mindspore_flags', '_parallel_inputs_run',
                   '_parameter_layout_dict', '_already_run', '_params_list', '_tensor_list', '_phase',
                   '_auto_parallel_mode', '_backward_hook', '_bprop_debug', '_is_run', '_param_prefix',
                   '_attr_synced', 'enable_hook', 'pynative', 'requires_grad',
                   '_auto_parallel_compile_and_run', 'cell_type']

    def __init__(self, auto_prefix=True, flags=None):
        Cell_.__init__(self, self._cell_tag)
        self._params = OrderedDict()
        self._cells = OrderedDict()
        self._params_list = OrderedDict()
        self._tensor_list = OrderedDict()
        self.training = False
        self.requires_grad = False
        self.pynative = False
        self._attr_synced = False
        self._param_prefix = ''
        self._auto_prefix = auto_prefix
        self._scope = None
        self._phase = 'train'
        self._parameter_layout_dict = {}
        self._create_time = int(time.time() * 1e9)
        init_backend()

        # call gc to release GE session resources used by non-used cell objects
        if os.getenv('GC_COLLECT_IN_CELL') == '1':
            gc.collect()

        self._construct_inputs_num = 0
        self._construct_inputs_names = []
        self._auto_parallel_mode = False
        self._parallel_inputs_run = None
        if flags:
            self.add_flags(**flags)
        self._backward_hook = None
        self.enable_hook = False
        self._bprop_debug = False
        self._already_run = False
        self.cell_type = None
        self._auto_parallel_compile_and_run = False

    @property
    def already_run(self):
        return self._already_run

    def __getstate__(self):
        base = Cell_.__getstate__(self)
        return base, self.__dict__

    def __setstate__(self, state):
        base, dict_ = state
        Cell_.__setstate__(self, base)
        self.__dict__ = dict_
        self._attr_synced = False

    @property
    def _cell_tag(self):
        # `<class 'xxxxxxx'>` to `xxxxxxx`
        return str(self.__class__)[8:-2]

    @already_run.setter
    def already_run(self, value):
        self._already_run = value

    @property
    def create_time(self):
        return self._create_time

    @property
    def cell_init_args(self):
        return self._cell_init_args

    @property
    def param_prefix(self):
        """
        Param prefix is the prefix of current cell's direct child parameter.
        """
        return self._param_prefix

    @property
    def bprop_debug(self):
        """
        Get whether cell custom bprop debug is enabled.
        """
        return self._bprop_debug

    @bprop_debug.setter
    def bprop_debug(self, value):
        """
        Set whether to enable cell custom bprop debug.

        Note:
            When bprop is defined in cell, the bprop function will be executed
            in python interpreter when bprop debug is true, and will be parsed
            and add to graph when bprop debug is false.

        Args:
            value (bool): Specifies whether to enable bprop debug. Default: False.
        """
        if not isinstance(value, bool):
            raise TypeError("'bprop debug' value must be bool type.")
        self._bprop_debug = value

    def update_cell_prefix(self):
        """
        Update the all child cells' self.param_prefix.

        After being invoked, it can get all the cell's children's name prefix by '_param_prefix'.
        """
        cells_name = self.cells_and_names()

        for cell_name, cell in cells_name:
            cell._param_prefix = cell_name

    def update_cell_type(self, cell_type):
        """
        The current cell type is updated when a quantization aware training network is encountered.

        After being invoked, it can set the cell type to 'cell_type'.
        """
        self.cell_type = cell_type

    @cell_init_args.setter
    def cell_init_args(self, value):
        if not isinstance(value, str):
            raise TypeError("'cell_init_args' must be string type.")
        self._cell_init_args = value

    @property
    def phase(self):
        return self._phase

    @phase.setter
    def phase(self, value):
        if not isinstance(value, str):
            raise TypeError("'phase' must be string type.")
        self._phase = value

    @property
    def parameter_layout_dict(self):
        return self._parameter_layout_dict

    @property
    def cls_name(self):
        return self.__class__.__name__

    @parameter_layout_dict.setter
    def parameter_layout_dict(self, value):
        if not isinstance(value, dict):
            raise TypeError("'parameter_layout_dict' must be dict type.")
        self._parameter_layout_dict = value

    def get_func_graph_proto(self):
        """Return graph binary proto."""
        return _executor._get_func_graph_proto(self.phase + "." + str(self.create_time), "anf_ir", True)

    def __getattr__(self, name):
        if '_params' in self.__dict__:
            params = self.__dict__['_params']
            if name in params:
                if context.get_context("mode") == context.PYNATIVE_MODE:
                    return self.cast_param(params[name])
                return params[name]
        if '_cells' in self.__dict__:
            cells = self.__dict__['_cells']
            if name in cells:
                return cells[name]
        if '_tensor_list' in self.__dict__:
            tensor_list = self.__dict__['_tensor_list']
            if name in tensor_list:
                return self.cast_param(tensor_list[name])
        if '_params_list' in self.__dict__:
            params_list = self.__dict__['_params_list']
            if name in params_list:
                para_list = params_list[name]
                cast_list = list()
                for para in para_list:
                    cast_list.append(self.cast_param(para))
                para_list = ParameterTuple(cast_list)
                return para_list
        raise AttributeError("'{}' object has no attribute '{}'.".format(type(self).__name__, name))

    def __del__(self):
        _pynative_exec.clear(str(id(self)))
        if hasattr(self, "_create_time"):
            _executor.del_net_res(str(self._create_time))

    def __delattr__(self, name):
        if name in self._params:
            del self._params[name]
        elif name in self._cells:
            del self._cells[name]
        else:
            if '_params_list' in self.__dict__ and name in self._params_list:
                del self._params_list[name]
            elif '_tensor_list' in self.__dict__ and name in self._tensor_list:
                del self._tensor_list[name]
            object.__delattr__(self, name)
        self._attr_synced = False

    def cast_inputs(self, inputs, dst_type):
        res = list()
        for item in inputs:
            if isinstance(item, tuple):
                res.append(self.cast_inputs(item, dst_type))
            else:
                res.append(cast(item, dst_type))
        return tuple(res)

    def __call__(self, *inputs, **kwargs):
        if context.get_context("mode") == context.GRAPH_MODE:
            if kwargs:
                raise ValueError("For 'graph' mode, the outermost network does not support passing "
                                 "key-value pair parameters and variable key-value pair parameters.")
            if self.enable_hook:
                raise ValueError("The graph mode does not support hook function.")
            out = self.compile_and_run(*inputs)
            return out

        if kwargs:
            bound_args = inspect.signature(self.construct).bind(*inputs, **kwargs)
            inputs = bound_args.args
            kwargs = bound_args.kwargs
        for item in inputs:
            if isinstance(item, numpy.ndarray):
                raise TypeError("cell inputs should not be numpy array.")
        origin_grad = []
        if self.requires_grad is True:
            _pynative_exec.set_grad_flag(True)
            _pynative_exec.new_graph(self, *inputs, **kwargs)
            for cell in self.cells():
                origin_grad.append(cell.requires_grad)
                cell.set_grad(True)
        else:
            _pynative_exec.set_grad_flag(False)
        cast_inputs = list()
        if hasattr(self, "_mindspore_flags"):
            if self._mindspore_flags.get('fp16'):
                cast_inputs = self.cast_inputs(inputs, mstype.float16)
            if self._mindspore_flags.get('fp32'):
                cast_inputs = self.cast_inputs(inputs, mstype.float32)
        if not cast_inputs:
            cast_inputs = inputs
        if self.enable_hook:
            output = self._hook_construct(*cast_inputs, **kwargs)
        else:
            output = self.construct(*cast_inputs, **kwargs)
        if isinstance(output, Parameter):
            output = output.data
        if self.requires_grad is True:
            _pynative_exec.end_graph(self, output, *inputs, **kwargs)
            for i, cell in enumerate(self.cells()):
                cell.set_grad(origin_grad[i])
            self._already_run = True
        return output

    def _add_attr(self, name, value):
        if name and name[:2] != '__' and name not in Cell.IGNORE_LIST:
            super(Cell, self)._add_attr(name, value)

    def _sync_attr_for_compile(self):
        """Sync the attr to c++ object."""
        if self._attr_synced:
            return
        cells = self.__dict__.get('_cells')
        for key in cells:
            cell = cells[key]
            cell._sync_attr_for_compile()
            self._add_attr(key, cell)
        params = self.__dict__.get('_params')
        for key in params:
            if '.' in key:
                continue
            param = params[key]
            self._add_attr(key, param)
        params_list = self.__dict__.get('_params_list')
        for key in params_list:
            params_list_item = params_list[key]
            self._add_attr(key, params_list_item)
        for key in self.__dict__:
            value = self.__dict__[key]
            self._add_attr(key, value)
        self._attr_synced = True

    def __setattr__(self, name, value):
        cells = self.__dict__.get('_cells')
        params = self.__dict__.get('_params')
        params_list = self.__dict__.get('_params_list')
        tensor_list = self.__dict__.get('_tensor_list')
        if isinstance(value, Parameter):
            if params is None:
                raise AttributeError("Can not assign params before Cell.__init__() call.")
            if name in self.__dict__:
                if self.__dict__[name] is not None:
                    raise TypeError("Expected type is not in (Parameter, Cell), but got Parameter.")
                del self.__dict__[name]
            if cells and name in cells:
                raise TypeError("Expected type is Cell, but got Parameter.")
            self.insert_param_to_cell(name, value)
        elif isinstance(value, ParameterTuple):
            if params is None:
                raise AttributeError("Can not assign params before Cell.__init__() call.")
            for item in value:
                self.insert_param_to_cell(item.name, item, check_name=False)
            if context.get_context("mode") == context.PYNATIVE_MODE:
                if name in self.__dict__:
                    del self.__dict__[name]
                if name in params:
                    del params[name]
                params_list[name] = value
            else:
                object.__setattr__(self, name, value)
        elif isinstance(value, Cell):
            if cells is None:
                raise AttributeError("Can not assign cells before Cell.__init__() call.")
            if name in self.__dict__:
                del self.__dict__[name]
            if params and name in params:
                raise TypeError("Expected type is Parameter, but got Cell.")
            if self._auto_prefix:
                value.update_parameters_name(name + '.')
            cells[name] = value
        elif params and name in params:
            if isinstance(value, Tensor) and self._params[name] is not None:
                self._params[name].set_data(value)
            elif value is not None:
                raise TypeError("Expected type in (Parameter, ParameterTuple), but got {}.".format(type(value)))
            else:
                self.insert_param_to_cell(name, None)
        elif cells and name in cells:
            if value is not None:
                raise TypeError("Expected type is cell, but got {}.".format(type(value)))
            self._cells[name] = None
        elif isinstance(value, Tensor):
            if context.get_context("mode") == context.PYNATIVE_MODE:
                if name in self.__dict__:
                    del self.__dict__[name]
                tensor_list[name] = value
            else:
                object.__setattr__(self, name, value)
        else:
            if isinstance(value, Primitive):
                value.set_prim_instance_name(name)
            object.__setattr__(self, name, value)
        if name not in Cell.IGNORE_LIST:
            self._attr_synced = False

    def extend_repr(self):
        """
        Sets the extended representation of the Cell.

        To print customized extended information, re-implement this method in your own cells.
        """
        return ''

    def __str__(self):
        return self.__repr__()

    def __repr__(self):
        extra_str = self.extend_repr()
        info_str = self.__class__.__name__ + '<'
        if self._cells:
            sub_str = '\n'
            if extra_str:
                sub_str += '{}\n'.format(self.extend_repr())
            for key, value in self._cells.items():
                sub_str += '({}): {}\n'.format(key, repr(value))
            sub_str = sub_str.replace('\n', '\n  ') + '>'
            info_str += sub_str
        else:
            info_str += extra_str + '>'
        return info_str

    def load_parameter_slice(self, params):
        """
        Replace parameters with sliced tensors by parallel strategies.

        Please refer to the usage in source code of `mindspore.common._Executor.compile`.

        Args:
            params (dict): The parameters dictionary used for initializing the data graph.
        """
        if params is None:
            params = self.parameters_dict()
        if isinstance(params, OrderedDict):
            for key in params:
                tensor = params[key].data
                if key not in self.parameter_layout_dict:
                    logger.info("layout dict does not contain the key %s.", key)
                    continue
                if params[key].sliced:
                    logger.debug("Param %s is already sliced.", key)
                    continue
                layout = self.parameter_layout_dict[key]
                new_tensor = _load_tensor_by_layout(tensor, layout)
                params[key].set_data(new_tensor, True)
        else:
            raise TypeError("Parameters need OrderedDict type, but got {}.".format(type(params)))

    def _load_inputs(self, *inputs):
        """
        Slice inputs tensors by parallel strategies.

        Args:
            inputs (Function or Cell): inputs of construct method.
        """
        parallel_inputs_run = []
        # judge if *args exists in input
        if self.argspec[1] is not None:
            prefix = self.argspec[1]
            for i in range(len(inputs)):
                key = prefix + str(i)
                self._construct_inputs_names = self._construct_inputs_names + (key,)
                self._construct_inputs_num = self._construct_inputs_num + 1
        for i, tensor in enumerate(inputs):
            key = self._construct_inputs_names[i]
            # if input is not used, self.parameter_layout_dict may not contain the key
            if key not in self.parameter_layout_dict:
                logger.warning("Layout dict does not contain the key %s.", key)
                parallel_inputs_run.append(tensor)
            else:
                layout = self.parameter_layout_dict[key]
                new_tensor = _load_tensor_by_layout(tensor, layout)
                parallel_inputs_run.append(new_tensor)
        return tuple(parallel_inputs_run)

    def set_parallel_input_with_inputs(self, *inputs):
        """
        Slice inputs tensors by parallel strategies, and set the sliced inputs to `_parallel_input_run`

        Args:
            inputs (tuple): inputs of construct method.
        """
        self._parallel_inputs_run = self._load_inputs(*inputs)

    def _get_construct_inputs_number_and_name(self):
        """Compute self._construct_inputs_names and self._construct_inputs_num"""
        from mindspore._extends.parse.parser import get_parse_method_of_class

        fn = get_parse_method_of_class(self)
        self.argspec = inspect.getfullargspec(fn)
        self._construct_inputs_num = fn.__code__.co_argcount
        self._construct_inputs_names = fn.__code__.co_varnames

        assert self._construct_inputs_num > 0
        assert self._construct_inputs_names[0] == 'self'
        assert self._construct_inputs_num - 1 <= len(self._construct_inputs_names)
        self._construct_inputs_names = self._construct_inputs_names[1:self._construct_inputs_num]
        self._construct_inputs_num = self._construct_inputs_num - 1

    def compile(self, *inputs):
        """
        Compiles cell.

        Args:
            inputs (tuple): Input parameters.
        """
        _executor.compile(self, *inputs, phase=self.phase, auto_parallel_mode=self._auto_parallel_mode)

    def compile_and_run(self, *inputs):
        """
        Compiles and runs cell.

        Args:
            inputs (tuple): Input parameters.

        Returns:
            Object, the result of executing.
        """
        self._auto_parallel_compile_and_run = True
        self.compile(*inputs)

        if self._auto_parallel_mode:
            if inputs and isinstance(inputs[0], Tensor) and inputs[0].virtual_flag:
                # get parallel inputs in sink mode, parallel inputs set in _executor.compile
                parallel_inputs_run = self._parallel_inputs_run
            else:
                parallel_inputs_run = inputs
            return _executor(self, *parallel_inputs_run, phase=self.phase)
        return _executor(self, *inputs, phase=self.phase)

    def auto_parallel_compile_and_run(self):
        return self._auto_parallel_compile_and_run

    def exec_checkpoint_graph(self):
        """Executes saving checkpoint graph operation."""
        _executor(self, phase='save')

    def insert_param_to_cell(self, param_name, param, check_name=True):
        """
        Adds a parameter to the current cell.

        Inserts a parameter with given name to the cell. Please refer to the usage in
        source code of `mindspore.nn.Cell.__setattr__`.

        Args:
            param_name (str): Name of the parameter.
            param (Parameter): Parameter to be inserted to the cell.
            check_name (bool): Determines whether the name input is compatible. Default: True.

        Raises:
            KeyError: If the name of parameter is null or contains dot.
            AttributeError: If user did not call init() first.
            TypeError: If the type of parameter is not Parameter.
        """
        if not param_name:
            raise KeyError("The name of parameter should not be null.")
        if check_name and '.' in param_name:
            raise KeyError("The name of parameter should not contain \".\"")
        if '_params' not in self.__dict__:
            raise AttributeError("You need call init() first.")
        if hasattr(self, param_name) and param_name not in self._params:
            raise KeyError("Duplicated parameter name '{}'.".format(param_name))
        if not isinstance(param, Parameter) and param is not None:
            raise TypeError("The type of parameter should be 'Parameter' if not None.")
        self._params[param_name] = param

    def cast_param(self, param):
        """
        Cast parameter according to auto mix precision level in pynative mode.

        Args:
            param (Parameter): The parameter to cast.
        """
        if hasattr(self, "_mindspore_flags"):
            if self._mindspore_flags.get('fp32'):
                param.set_cast_dtype(mstype.float32)
            elif self._mindspore_flags.get('fp16'):
                param.set_cast_dtype(mstype.float16)
            else:
                # retest dtype
                param.set_cast_dtype()
        return param

    def insert_child_to_cell(self, child_name, child_cell):
        """
        Adds a child cell to the current cell with a given name.

        Args:
            child_name (str): Name of the child cell.
            child_cell (Cell): The child cell to be inserted.

        Raises:
            KeyError: Child Cell's name is incorrect or duplicated with the other child name.
            TypeError: Child Cell's type is incorrect.
        """
        if not child_name or '.' in child_name:
            raise KeyError("Child cell name is incorrect.")
        if hasattr(self, child_name) and child_name not in self._cells:
            raise KeyError("Duplicate child name '{}'.".format(child_name))
        if not isinstance(child_cell, Cell) and child_cell is not None:
            raise TypeError("Child cell type is incorrect.")
        self._cells[child_name] = child_cell

    def construct(self, *inputs, **kwargs):
        """
        Defines the computation to be performed. This method must be overridden by all subclasses.

        Note:
            The inputs of the top cell only allow Tensor.
            Other types (tuple, list, int etc.) are forbidden.

        Returns:
            Tensor, returns the computed result.
        """
        raise NotImplementedError

    def init_parameters_data(self, auto_parallel_mode=False):
        """
        Initialize all parameters and replace the original saved parameters in cell.

        Notes:
            trainable_params() and other similar interfaces may return different parameter instance after
            `init_parameters_data`, do not save these result.

        Args:
            auto_parallel_mode (bool): If running in auto_parallel_mode.

        Returns:
            Dict[Parameter, Parameter], returns a dict of original parameter and replaced parameter.
        """
        replace = dict()
        def _updata(param):
            if param in replace:
                return replace[param]
            layout = None
            set_sliced = False
            if auto_parallel_mode:
                set_sliced = True
                if param.name not in self.parameter_layout_dict:
                    logger.debug("Layout dict does not contain the key %s.", param.name)
                else:
                    layout = self.parameter_layout_dict[param.name]
            new_p = param.init_data(layout, set_sliced=set_sliced)
            replace[param] = new_p
            return new_p
        # replace all original usage.
        cells = self.cells_and_names()
        for _, cell in cells:
            params = cell._params.items()
            for param_name, param in params:
                cell._params[param_name] = _updata(param)
            cell_dict = cell.__dict__
            for key in cell_dict:
                if isinstance(cell_dict[key], ParameterTuple):
                    param_tuple = cell_dict[key]
                    new_param_tuple = []
                    for param in param_tuple:
                        new_param_tuple.append(_updata(param))
                    cell.__dict__[key] = ParameterTuple(new_param_tuple)
        return replace

    def parameters_dict(self, recurse=True):
        """
        Gets parameters dictionary.

        Gets the parameters dictionary of this cell.

        Args:
            recurse (bool): Whether contains the parameters of subcells. Default: True.

        Returns:
            OrderedDict, return parameters dictionary.
        """
        param_dict = OrderedDict()
        for param in self.get_parameters(expand=recurse):
            param_dict[param.name] = param
        return param_dict

    def parameters_broadcast_dict(self, recurse=True):
        param_dict = OrderedDict()
        for param in self.get_parameters(expand=recurse):
            if param.layerwise_parallel is False:
                param_dict[param.name] = param
        if not param_dict:
            return None
        return param_dict

    def update_parameters_name(self, prefix='', recurse=True):
        """
        Updates the names of parameters with given prefix string.

        Adds the given prefix to the names of parameters.

        Args:
            prefix (str): The prefix string.
            recurse (bool): Whether contains the parameters of subcells. Default: True.
        """

        Validator.check_str_by_regular(prefix)
        for name, param in self.parameters_and_names(expand=recurse):
            if prefix != '':
                param.is_init = False
            param.name = prefix + name

    def trainable_params(self, recurse=True):
        """
        Returns all trainable parameters.

        Returns a list of all trainable parmeters.

        Args:
            recurse (bool): Whether contains the trainable parameters of subcells. Default: True.

        Returns:
            List, the list of trainable parameters.
        """
        return list(filter(lambda x: x.requires_grad, self.get_parameters(expand=recurse)))

    def untrainable_params(self, recurse=True):
        """
        Returns all untrainable parameters.

        Returns a list of all untrainable parameters.

        Args:
            recurse (bool): Whether contains the untrainable parameters of subcells. Default: True.

        Returns:
            List, the list of untrainable parameters.
        """
        return list(filter(lambda x: not x.requires_grad, self.get_parameters(expand=recurse)))

    def get_parameters(self, expand=True):
        """
        Returns an iterator over cell parameters.

        Yields parameters of this cell. If `expand` is True, yield parameters of this cell and all subcells.

        Args:
            expand (bool): If true, yields parameters of this cell and all subcells. Otherwise, only yield parameters
                           that are direct members of this cell. Default: True.

        Examples:
            >>> net = Net()
            >>> for item in net.get_parameters():
            >>>     print(item)
        """
        for _, param in self.parameters_and_names(expand=expand):
            yield param

    def check_names(self):
        names = set("")
        for value, param in self.parameters_and_names():
            if param.name in names:
                raise ValueError("The value of {} is {}, its name '{}' already exists.".
                                 format(value, param, param.name))
            names.add(param.name)

    def parameters_and_names(self, name_prefix='', expand=True):
        """
        Returns an iterator over cell parameters.

        Includes the parameter's name  and itself.

        Args:
            name_prefix (str): Namespace. Default: ''.
            expand (bool): If true, yields parameters of this cell and all subcells. Otherwise, only yield parameters
                           that are direct members of this cell. Default: True.

        Examples:
            >>> n = Net()
            >>> names = []
            >>> for m in n.parameters_and_names():
            >>>     if m[0]:
            >>>         names.append(m[0])
        """
        cells = []
        if expand:
            cells = self.cells_and_names(name_prefix=name_prefix)
        else:
            cells.append((name_prefix, self))

        params_set = set()
        for cell_name, cell in cells:
            params = cell._params.items()
            for par_name, par in params:
                if par.inited_param is not None:
                    par = par.inited_param
                if par is not None and id(par) not in params_set:
                    params_set.add(id(par))
                    par_new_name = par_name
                    if cell_name:
                        par_new_name = cell_name + '.' + par_new_name

                    yield par_new_name, par

    def cells_and_names(self, cells=None, name_prefix=''):
        """
        Returns an iterator over all cells in the network.

        Includes the cell's name and itself.

        Args:
            cells (str): Cells to iterate over. Default: None.
            name_prefix (str): Namespace. Default: ''.

        Examples:
            >>> n = Net()
            >>> names = []
            >>> for m in n.cells_and_names():
            >>>     if m[0]:
            >>>         names.append(m[0])
        """
        t_cells = cells if cells else set()
        if self in t_cells:
            return

        t_cells.add(self)
        yield name_prefix, self

        for name, cell in self._cells.items():
            if cell:
                cells_name_prefix = name
                if name_prefix:
                    cells_name_prefix = name_prefix + '.' + cells_name_prefix
                for ele in cell.cells_and_names(t_cells, cells_name_prefix):
                    yield ele

    def cells(self):
        """Returns an iterator over immediate cells."""
        return self.name_cells().values()

    def _set_scope(self, name):
        """Sets the name on the first time."""
        if self._scope is None:
            self._scope = name

    def _children_scope_recursive(self, parent_prefix='Default'):
        """Generates the scope of each layer of the network recursively."""
        reserve_class_name_in_scope = context.get_context("reserve_class_name_in_scope")

        for name, cell in self.name_cells().items():
            yield parent_prefix + "/" + name + (("-" + cell.__class__.__name__)
                                                if reserve_class_name_in_scope else ""), cell

        for name, cell in self.name_cells().items():
            for key, value in cell._children_scope_recursive(parent_prefix + "/" + name +
                                                             (("-" + cell.__class__.__name__)
                                                              if reserve_class_name_in_scope else "")):
                yield key, value

    def get_scope(self):
        """Returns the scope of a cell object in one network."""
        return self._scope

    def generate_scope(self):
        """Generate the scope for each cell object in the network."""
        for name, cell in self._children_scope_recursive():
            cell._set_scope(name)

    def name_cells(self):
        """
        Returns an iterator over all cells in the network.

        Include name of the cell and cell itself.
        """
        value_set = set()
        cells = OrderedDict()
        for name, cell in self._cells.items():
            if cell is not None and cell not in value_set:
                value_set.add(cell)
                cells[name] = cell
        return cells

    def add_flags(self, **flags):
        if not hasattr(self, "_mindspore_flags"):
            self._mindspore_flags = {}
        self._mindspore_flags.update({**flags})
        self.__dict__.update({**flags})
        return self

    def add_flags_recursive(self, **flags):
        self.add_flags(**flags)
        if hasattr(self, '_cell_init_args'):
            self._cell_init_args += str({**flags})
        for cell in self.cells():
            cell.add_flags_recursive(**flags)
        return self

    def get_flags(self):
        if not hasattr(self, "_mindspore_flags"):
            self._mindspore_flags = {}
        return self._mindspore_flags

    def to_float(self, dst_type):
        """
        Add cast on all inputs of cell and child cells to run with certain float type.

        If `dst_type is mindspore.dtype.float16`, all the inputs of Cell including input, Parameter, Tensor
        as const will be cast to float16. Please refer to the usage in source code of
        `mindspore.train.amp.build_train_network`.

        Note:
            Multiple calls will overwrite.

        Args:
            dst_type (:class:`mindspore.dtype`): Transfer Cell to Run with dst_type.
                dst_type can be `mindspore.dtype.float16` or `mindspore.dtype.float32`.

        Raises:
            ValueError: If dst_type is not float32 nor float16.
        """
        if dst_type not in (mstype.float16, mstype.float32):
            raise ValueError("dst_type should inside float32 or float16.")
        flags = {'fp16': dst_type == mstype.float16, 'fp32': dst_type == mstype.float32}
        self.add_flags_recursive(**flags)
        return self

    def set_grad(self, requires_grad=True):
        """
        Sets the cell flag for gradient.

        Args:
            requires_grad (bool): Specifies if the net need to grad, if it is
                True, cell will construct backward network in pynative mode. Default: True.
        """
        self.requires_grad = requires_grad
        return self

    def set_train(self, mode=True):
        """
        Sets the cell to training mode.

        The cell itself and all children cells will be set to training mode.

        Args:
            mode (bool): Specifies whether the model is training. Default: True.
        """
        if mode is False:
            self._phase = 'predict'
        else:
            self._phase = 'train'
        self.add_flags_recursive(training=mode)
        return self

    def set_broadcast_flag(self, mode=True):
        """
        Set the cell to data_parallel mode.

        The cell can be accessed as an attribute using the given name.

        Args:
            mode (bool): Specifies whether the model is data_parallel. Default: True.
        """
        self.add_flags_recursive(broadcast_flag=mode)
        return self

    def set_auto_parallel(self):
        """
        Set the cell to auto parallel mode.

        Note:
            If a cell needs to use the auto parallel or semi auto parallel mode for training, evaluation or prediction,
            this interface needs to be called by the cell.
        """
        self._auto_parallel_mode = True
        self.add_flags(auto_parallel=True)
        self._get_construct_inputs_number_and_name()

    def _hook_construct(self, *inputs, **kwargs):
        """Hook construct method to replace original construct method when hook function enabled."""
        inputs = self._backward_hook(*inputs)
        inputs = self.construct(inputs)
        outputs = self._backward_hook(inputs)
        return outputs

    def register_backward_hook(self, fn):
        """
        Set the cell backward hook function. Note that this function is only supported in Pynative Mode.

        Note:
            fn must be defined as the following code. `cell_name` is the name of registered cell.
            `grad_input` is gradient passed to the cell. `grad_output` is the gradient computed and passed to the
            next cell or primitve, which may be modified and returned.
            >>> hook_fn(cell_name, grad_input, grad_output) -> Tensor or None

        Args:
            fn (function): Specifies the hook function with grad as input.

        """
        self._backward_hook = HookBackward(fn, self.cls_name + "(" + str(id(self)) + ")")
        self.enable_hook = True

    def set_param_ps(self, recurse=True, init_in_server=False):
        """
        Set whether the trainable parameter is updated by parameter server.

        Note:
            It only works when a running task is in the parameter server mode.

        Args:
            recurse (bool): Whether sets the trainable parameters of subcells. Default: True.
        """
        params = self.trainable_params(recurse)
        for param in params:
            param.set_param_ps(init_in_server)


class GraphKernel(Cell):
    """
    Base class for GraphKernel.

    A `GraphKernel` a composite of basic primitives and can be compiled into a fused kernel automatically when
    enable_graph_kernel in context is set to True.

    Examples:
        >>> class Relu(GraphKernel):
        >>>    def __init__(self):
        >>>        super(Relu, self).__init__()
        >>>        self.max = P.Maximum()
        >>>
        >>>    def construct(self, x):
        >>>        return self.max(P.Fill()(P.DType()(x), P.Shape()(x), 0.0), x)
    """

    def __init__(self, auto_prefix=True, pips=None):
        super(GraphKernel, self).__init__(auto_prefix, pips)
        class_name = self.__class__.__name__
        self.add_flags(graph_kernel=class_name)

    def construct(self):
        raise NotImplementedError