分类目录:《深入浅出Pytorch函数》总目录
相关文章:
· 深入浅出Pytorch函数------torch.nn.init.calculate_gain
· 深入浅出Pytorch函数------torch.nn.init.uniform_
· 深入浅出Pytorch函数------torch.nn.init.normal_
· 深入浅出Pytorch函数------torch.nn.init.constant_
· 深入浅出Pytorch函数------torch.nn.init.ones_
· 深入浅出Pytorch函数------torch.nn.init.zeros_
· 深入浅出Pytorch函数------torch.nn.init.eye_
· 深入浅出Pytorch函数------torch.nn.init.dirac_
· 深入浅出Pytorch函数------torch.nn.init.xavier_uniform_
· 深入浅出Pytorch函数------torch.nn.init.xavier_normal_
· 深入浅出Pytorch函数------torch.nn.init.kaiming_uniform_
· 深入浅出Pytorch函数------torch.nn.init.kaiming_normal_
· 深入浅出Pytorch函数------torch.nn.init.trunc_normal_
· 深入浅出Pytorch函数------torch.nn.init.orthogonal_
· 深入浅出Pytorch函数------torch.nn.init.sparse_
torch.nn.init
模块中的所有函数都用于初始化神经网络参数,因此它们都在torc.no_grad()
模式下运行,autograd
不会将其考虑在内。
根据He, K等人于2015年在《Delving deep into rectifiers: Surpassing human-level performance on ImageNet classification》中描述的方法,用一个正态分布生成值,填充输入的张量或变量。结果张量中的值采样自 N ( 0 , std 2 ) N(0, \text{std}^2) N(0,std2),其中:
std = gain fan_mode \text{std} = \frac{\text{gain}}{\sqrt{\text{fan\_mode}}} std=fan_mode gain
这种方法也被称为He initialisation。
语法
torch.nn.init.kaiming_normal_(tensor, a=0, mode='fan_in', nonlinearity='leaky_relu')
参数
tensor
:[Tensor
] 一个 N N N维张量torch.Tensor
a
:[float
] 这层之后使用的rectifier的斜率系数(ReLU的默认值为0)mode
:[str
] 可以为fan_in
或fan_out
。若为fan_in
则保留前向传播时权值方差的量级,若为fan_out
则保留反向传播时的量级,默认值为fan_in
。nonlinearity
:[str
] 一个非线性函数,即一个nn.functional
的名称,推荐使用relu
或者leaky_relu
,默认值为leaky_relu
。
返回值
一个torch.Tensor
且参数tensor
也会更新
实例
w = torch.empty(3, 5)
nn.init.kaiming_normal_(w, mode='fan_out', nonlinearity='relu')
函数实现
def kaiming_normal_(
tensor: Tensor, a: float = 0, mode: str = 'fan_in', nonlinearity: str = 'leaky_relu'
):
r"""Fills the input `Tensor` with values according to the method
described in `Delving deep into rectifiers: Surpassing human-level
performance on ImageNet classification` - He, K. et al. (2015), using a
normal distribution. The resulting tensor will have values sampled from
:math:`\mathcal{N}(0, \text{std}^2)` where
.. math::
\text{std} = \frac{\text{gain}}{\sqrt{\text{fan\_mode}}}
Also known as He initialization.
Args:
tensor: an n-dimensional `torch.Tensor`
a: the negative slope of the rectifier used after this layer (only
used with ``'leaky_relu'``)
mode: either ``'fan_in'`` (default) or ``'fan_out'``. Choosing ``'fan_in'``
preserves the magnitude of the variance of the weights in the
forward pass. Choosing ``'fan_out'`` preserves the magnitudes in the
backwards pass.
nonlinearity: the non-linear function (`nn.functional` name),
recommended to use only with ``'relu'`` or ``'leaky_relu'`` (default).
Examples:
>>> w = torch.empty(3, 5)
>>> nn.init.kaiming_normal_(w, mode='fan_out', nonlinearity='relu')
"""
if 0 in tensor.shape:
warnings.warn("Initializing zero-element tensors is a no-op")
return tensor
fan = _calculate_correct_fan(tensor, mode)
gain = calculate_gain(nonlinearity, a)
std = gain / math.sqrt(fan)
with torch.no_grad():
return tensor.normal_(0, std)