Source code for mindspore.nn.layer.timedistributed

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"""Time Distributed."""

from mindspore.ops.primitive import constexpr, Primitive
from mindspore.ops import Reshape, Transpose, Stack, Unstack
from mindspore.common import Tensor
from mindspore._checkparam import Validator
from ..cell import Cell

__all__ = ['TimeDistributed']


@constexpr
def _check_reshape_pos(reshape_pos, inputs_shape, outputs_shape, prim_name=None):
    msg_prefix = f"For '{prim_name}', the" if prim_name else "The"
    if reshape_pos >= len(outputs_shape) or inputs_shape[reshape_pos] != outputs_shape[reshape_pos]:
        raise ValueError(f"{msg_prefix} 'reshape_with_axis' is invalid in the input and output. "
                         f"The 'reshape_pos' should be less than the length of 'outputs_shape', and the "
                         f"'inputs_shape[reshape_pos]' should be equal to 'outputs_shape[reshape_pos]', but got "
                         f"'reshape_pos': {reshape_pos}, 'inputs_shape': {inputs_shape}, 'outputs_shape': "
                         f"{outputs_shape}. You may try pass parameters without 'reshape_with_axis'.")


@constexpr
def _check_expand_dims_axis(time_axis, ndim, prim_name=None):
    msg_prefix = f"For '{prim_name}', the" if prim_name else "The"
    if time_axis > ndim:
        raise ValueError(f"{msg_prefix} value of 'time_axis' should be in range of [{-ndim - 1}, {ndim}], "
                         f"but got {time_axis}.")


@constexpr
def _generate_perm(axis_a, axis_b, length):
    perm = tuple(range(length))
    axis_a, axis_b = (axis_a, axis_b) if axis_a < axis_b else (axis_b, axis_a)
    return perm[:axis_a] + (perm[axis_b],) + perm[axis_a: axis_b] + perm[axis_b + 1:]


@constexpr
def _check_data(flag, prim_name=None):
    msg_prefix = f"For '{prim_name}', the" if prim_name else "The"
    if not flag:
        raise TypeError(f"{msg_prefix} inputs and outputs should be a Tensor.")


@constexpr
def _check_inputs_dim(shape, prim_name=None):
    msg_prefix = f"For '{prim_name}', the" if prim_name else "The"
    if len(shape) < 3:
        raise ValueError(f"{msg_prefix} inputs shape should be at least 3D, but got {len(shape)}.")


[docs]class TimeDistributed(Cell): r""" The time distributed layer. Time distributed is a wrapper which allows to apply a layer to every temporal slice of an input. And the `x` should be at least 3D. There are two cases in the implementation. When reshape_with_axis provided, the reshape method will be chosen, which is more efficient; otherwise, the method of dividing the inputs along time axis will be used, which is more general. For example, reshape_with_axis could not be provided when deal with Batch Normalization. Args: layer(Union[Cell, Primitive]): The Cell or Primitive which will be wrapped. time_axis(int): The axis of time_step. reshape_with_axis(int): The axis which will be reshaped with time_axis. Default: None. Inputs: - **x** (Tensor) - Tensor of shape :math:`(N, T, *)`, where :math:`*` means any number of additional dimensions. Outputs: Tensor of shape :math:`(N, T, *)` Supported Platforms: ``Ascend`` ``GPU`` ``CPU`` Raises: TypeError: If layer is not a Cell or Primitive. Examples: >>> x = Tensor(np.random.random([32, 10, 3]), mindspore.float32) >>> dense = nn.Dense(3, 6) >>> net = nn.TimeDistributed(dense, time_axis=1, reshape_with_axis=0) >>> output = net(x) >>> print(output.shape) (32, 10, 6) """ def __init__(self, layer, time_axis, reshape_with_axis=None): """Initialize TimeDistributed.""" if not isinstance(layer, (Cell, Primitive)): raise TypeError(f"For '{self.cls_name}', the 'layer' should be Cell or Primitive instance, " f"but got type: {type(layer).__name__}.") super(TimeDistributed, self).__init__() Validator.check_is_int(time_axis, "time_axis", self.cls_name) if reshape_with_axis is not None: Validator.check_is_int(reshape_with_axis, "reshape_with_axis", self.cls_name) self.layer = layer self.time_axis = time_axis self.reshape_with_axis = reshape_with_axis self.transpose = Transpose() self.reshape = Reshape() def construct(self, inputs): _check_data(isinstance(inputs, Tensor), self.cls_name) _check_inputs_dim(inputs.shape, self.cls_name) time_axis = self.time_axis % len(inputs.shape) if self.reshape_with_axis is not None: reshape_with_axis = self.reshape_with_axis % len(inputs.shape) inputs_shape = inputs.shape time_axis_new = len(inputs_shape) - 2 if reshape_with_axis == len(inputs_shape) - 1 \ else (reshape_with_axis + 1 if time_axis > reshape_with_axis else reshape_with_axis - 1) reshape_pos = time_axis_new if time_axis_new < reshape_with_axis else reshape_with_axis perm = _generate_perm(time_axis_new, time_axis, len(inputs_shape)) inputs = self.transpose(inputs, perm) inputs_shape_new = inputs.shape inputs = self.reshape(inputs, inputs_shape_new[: reshape_pos] + (-1,) + inputs_shape_new[reshape_pos + 2:]) outputs = self.layer(inputs) _check_data(isinstance(outputs, Tensor), self.cls_name) _check_reshape_pos(reshape_pos, inputs.shape, outputs.shape, self.cls_name) outputs_shape_new = outputs.shape[:reshape_pos] + inputs_shape_new[reshape_pos: reshape_pos + 2] if reshape_pos + 1 < len(outputs.shape): outputs_shape_new += outputs.shape[reshape_pos + 1:] return self.reshape(outputs, outputs_shape_new) unstack = Unstack(time_axis) inputs = unstack(inputs) y = () for item in inputs: outputs = self.layer(item) _check_data(isinstance(outputs, Tensor), self.cls_name) _check_expand_dims_axis(time_axis, outputs.ndim, self.cls_name) y += (outputs,) y = Stack(time_axis)(y) return y