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# Copyright 2020 Huawei Technologies Co., Ltd |
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# |
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# Licensed under the Apache License, Version 2.0 (the "License"); |
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# you may not use this file except in compliance with the License. |
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# You may obtain a copy of the License at |
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# |
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# http://www.apache.org/licenses/LICENSE-2.0 |
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# |
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# Unless required by applicable law or agreed to in writing, software |
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# distributed under the License is distributed on an "AS IS" BASIS, |
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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# See the License for the specific language governing permissions and |
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# limitations under the License. |
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# ============================================================================ |
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"""weight initial""" |
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import math |
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import numpy as np |
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from mindspore.common import initializer as init |
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import mindspore.nn as nn |
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from mindspore import Tensor |
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def calculate_gain(nonlinearity, param=None): |
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r"""Return the recommended gain value for the given nonlinearity function. |
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The values are as follows: |
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================= ==================================================== |
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nonlinearity gain |
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================= ==================================================== |
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Linear / Identity :math:`1` |
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Conv{1,2,3}D :math:`1` |
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Sigmoid :math:`1` |
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Tanh :math:`\frac{5}{3}` |
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ReLU :math:`\sqrt{2}` |
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Leaky Relu :math:`\sqrt{\frac{2}{1 + \text{negative\_slope}^2}}` |
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================= ==================================================== |
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Args: |
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nonlinearity: the non-linear function (`nn.functional` name) |
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param: optional parameter for the non-linear function |
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""" |
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linear_fns = ['linear', 'conv1d', 'conv2d', 'conv3d', 'conv_transpose1d', 'conv_transpose2d', 'conv_transpose3d'] |
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gain = 0 |
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if nonlinearity in linear_fns or nonlinearity == 'sigmoid': |
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gain = 1 |
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elif nonlinearity == 'tanh': |
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gain = 5.0 / 3 |
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elif nonlinearity == 'relu': |
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gain = math.sqrt(2.0) |
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elif nonlinearity == 'leaky_relu': |
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if param is None: |
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negative_slope = 0.01 |
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elif not isinstance(param, bool) and isinstance(param, int) or isinstance(param, float): |
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# True/False are instances of int, hence check above |
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negative_slope = param |
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else: |
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raise ValueError("negative_slope {} not a valid number".format(param)) |
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gain = math.sqrt(2.0 / (1 + negative_slope ** 2)) |
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else: |
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raise ValueError("Unsupported nonlinearity {}".format(nonlinearity)) |
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return gain |
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def _calculate_correct_fan(array, mode): |
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mode = mode.lower() |
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valid_modes = ['fan_in', 'fan_out'] |
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if mode not in valid_modes: |
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raise ValueError("Mode {} not supported, please use one of {}".format(mode, valid_modes)) |
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fan_in, fan_out = _calculate_fan_in_and_fan_out(array) |
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return fan_in if mode == 'fan_in' else fan_out |
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def kaiming_uniform_(array, a=0, mode='fan_in', nonlinearity='leaky_relu'): |
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r"""Fills the input `Tensor` with values according to the method |
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described in `Delving deep into rectifiers: Surpassing human-level |
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performance on ImageNet classification` - He, K. et al. (2015), using a |
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uniform distribution. The resulting tensor will have values sampled from |
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:math:`\mathcal{U}(-\text{bound}, \text{bound})` where |
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.. math:: |
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\text{bound} = \text{gain} \times \sqrt{\frac{3}{\text{fan\_mode}}} |
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Also known as He initialization. |
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Args: |
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array: an n-dimensional `tensor` |
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a: the negative slope of the rectifier used after this layer (only |
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used with ``'leaky_relu'``) |
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mode: either ``'fan_in'`` (default) or ``'fan_out'``. Choosing ``'fan_in'`` |
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preserves the magnitude of the variance of the weights in the |
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forward pass. Choosing ``'fan_out'`` preserves the magnitudes in the |
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backwards pass. |
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nonlinearity: the non-linear function (`nn.functional` name), |
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recommended to use only with ``'relu'`` or ``'leaky_relu'`` (default). |
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""" |
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fan = _calculate_correct_fan(array, mode) |
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gain = calculate_gain(nonlinearity, a) |
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std = gain / math.sqrt(fan) |
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bound = math.sqrt(3.0) * std # Calculate uniform bounds from standard deviation |
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return np.random.uniform(-bound, bound, array.shape) |
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def kaiming_normal_(array, a=0, mode='fan_in', nonlinearity='leaky_relu'): |
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r"""Fills the input `Tensor` with values according to the method |
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described in `Delving deep into rectifiers: Surpassing human-level |
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performance on ImageNet classification` - He, K. et al. (2015), using a |
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normal distribution. The resulting tensor will have values sampled from |
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:math:`\mathcal{N}(0, \text{std}^2)` where |
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.. math:: |
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\text{std} = \frac{\text{gain}}{\sqrt{\text{fan\_mode}}} |
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Also known as He initialization. |
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Args: |
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array: an n-dimensional `tensor` |
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a: the negative slope of the rectifier used after this layer (only |
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used with ``'leaky_relu'``) |
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mode: either ``'fan_in'`` (default) or ``'fan_out'``. Choosing ``'fan_in'`` |
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preserves the magnitude of the variance of the weights in the |
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forward pass. Choosing ``'fan_out'`` preserves the magnitudes in the |
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backwards pass. |
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nonlinearity: the non-linear function (`nn.functional` name), |
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recommended to use only with ``'relu'`` or ``'leaky_relu'`` (default). |
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""" |
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fan = _calculate_correct_fan(array, mode) |
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gain = calculate_gain(nonlinearity, a) |
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std = gain / math.sqrt(fan) |
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return np.random.normal(0, std, array.shape) |
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def _calculate_fan_in_and_fan_out(array): |
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"""calculate the fan_in and fan_out for input array""" |
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dimensions = len(array.shape) |
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if dimensions < 2: |
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raise ValueError("Fan in and fan out can not be computed for array with fewer than 2 dimensions") |
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num_input_fmaps = array.shape[1] |
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num_output_fmaps = array.shape[0] |
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receptive_field_size = 1 |
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if dimensions > 2: |
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receptive_field_size = array[0][0].size |
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fan_in = num_input_fmaps * receptive_field_size |
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fan_out = num_output_fmaps * receptive_field_size |
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return fan_in, fan_out |
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def assignment(arr, num): |
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"""Assign the value of num to arr""" |
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if arr.shape == (): |
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arr = arr.reshape((1)) |
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arr[:] = num |
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arr = arr.reshape(()) |
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else: |
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if isinstance(num, np.ndarray): |
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arr[:] = num[:] |
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else: |
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arr[:] = num |
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return arr |
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class KaimingUniform(init.Initializer): |
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def __init__(self, a=0, mode='fan_in', nonlinearity='leaky_relu'): |
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super(KaimingUniform, self).__init__() |
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self.a = a |
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self.mode = mode |
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self.nonlinearity = nonlinearity |
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def _initialize(self, arr): |
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tmp = kaiming_uniform_(arr, self.a, self.mode, self.nonlinearity) |
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assignment(arr, tmp) |
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class KaimingNormal(init.Initializer): |
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def __init__(self, a=0, mode='fan_in', nonlinearity='leaky_relu'): |
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super(KaimingNormal, self).__init__() |
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self.a = a |
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self.mode = mode |
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self.nonlinearity = nonlinearity |
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def _initialize(self, arr): |
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tmp = kaiming_normal_(arr, self.a, self.mode, self.nonlinearity) |
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assignment(arr, tmp) |
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def default_recurisive_init(custom_cell): |
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"""weight init for conv2d and dense""" |
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for _, cell in custom_cell.cells_and_names(): |
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if isinstance(cell, nn.Conv2d): |
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cell.weight.default_input = init.initializer(KaimingUniform(a=math.sqrt(5)), |
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cell.weight.default_input.shape(), |
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cell.weight.default_input.dtype()) |
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if cell.bias is not None: |
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fan_in, _ = _calculate_fan_in_and_fan_out(cell.weight.default_input.asnumpy()) |
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bound = 1 / math.sqrt(fan_in) |
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cell.bias.default_input = Tensor(np.random.uniform(-bound, bound, |
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cell.bias.default_input.shape()), |
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cell.bias.default_input.dtype()) |
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elif isinstance(cell, nn.Dense): |
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cell.weight.default_input = init.initializer(KaimingUniform(a=math.sqrt(5)), |
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cell.weight.default_input.shape(), |
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cell.weight.default_input.dtype()) |
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if cell.bias is not None: |
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fan_in, _ = _calculate_fan_in_and_fan_out(cell.weight.default_input.asnumpy()) |
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bound = 1 / math.sqrt(fan_in) |
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cell.bias.default_input = Tensor(np.random.uniform(-bound, bound, |
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cell.bias.default_input.shape()), |
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cell.bias.default_input.dtype()) |
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elif isinstance(cell, (nn.BatchNorm2d, nn.BatchNorm1d)): |
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pass |