# Copyright 2022 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
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# ============================================================================
"""channel shuffle"""
from mindspore.ops.primitive import constexpr
from mindspore.ops import operations as P
from mindspore.nn.cell import Cell
__all__ = ['ChannelShuffle']
[文档]class ChannelShuffle(Cell):
r"""
Divide the channels in a tensor of shape :math:`(*, C , H, W)`
into g groups and rearrange them as :math:`(*, C \frac g, g, H, W)`,
while keeping the original tensor shape.
Args:
groups (int): Number of groups to divide channels in. Refer to :math:`g`.
Inputs:
- **x** (Tensor) - Tensor of shape :math:`(*, C_{in}, H_{in}, W_{in})`.
Outputs:
Tensor, with the same type and shape as the `x`.
Raises:
TypeError: If `groups` is not an int.
ValueError: If `groups` is less than 1.
ValueError: If dims of `x` is less than 3.
ValueError: If number of channels can not be divisible by groups.
Supported Platforms:
``Ascend`` ``GPU`` ``CPU``
Examples:
>>> channel_shuffle = nn.ChannelShuffle(2)
>>> x = Tensor(np.arange(16).astype(np.int32).reshape(1, 4, 2, 2))
>>> print(x)
[[[[0 1],
[2 3]],
[[4 5],
[6 7]],
[[8 9],
[10 11]],
[[12 13],
[14 15]],
]]
>>> output = channel_shuffle(x)
>>> print(output)
[[[[0 1],
[2 3]],
[[8 9],
[10 11]],
[[4 5],
[6 7]],
[[12 13],
[14 15]],
]]
"""
def __init__(self, groups):
"""Initialize ChannelShuffle."""
super(ChannelShuffle, self).__init__()
if not isinstance(groups, int):
raise TypeError("For ChannelShuffle, the param `groups` must be int, but got {}.".format(type(groups)))
if groups < 1:
raise ValueError(f"For ChannelShuffle, the param `groups` must be larger than 0, but got {groups}.")
self.groups = groups
self.shape = P.Shape()
self.reshape = P.Reshape()
self.transpose = P.Transpose()
@staticmethod
@constexpr
def _check_input_dim(shape, channels, groups, cls_name):
dim = len(shape)
if dim < 3:
raise ValueError(f"For {cls_name}, the in_shape must have more than 2 dims, but got {dim}.")
if channels % groups != 0:
raise ValueError(f"For {cls_name}, number of channels must be divisible by groups, "
f"but got {channels} channels and {groups} groups.")
def construct(self, x):
x_shape = self.shape(x)
n, c = x_shape[0], x_shape[1]
self._check_input_dim(x_shape, c, self.groups, self.cls_name)
out = self.reshape(x, (n, self.groups, c // self.groups, -1))
out = self.transpose(out, (0, 2, 1, 3))
return self.reshape(out, x_shape)