Source code for mmengine.model.weight_init
# Copyright (c) OpenMMLab. All rights reserved.
import copy
import math
import warnings
import numpy as np
import torch
import torch.nn as nn
from torch import Tensor
from mmengine.logging import print_log
from mmengine.registry import WEIGHT_INITIALIZERS, build_from_cfg
[docs]def update_init_info(module, init_info):
"""Update the `_params_init_info` in the module if the value of parameters
are changed.
Args:
module (obj:`nn.Module`): The module of PyTorch with a user-defined
attribute `_params_init_info` which records the initialization
information.
init_info (str): The string that describes the initialization.
"""
assert hasattr(
module,
'_params_init_info'), f'Can not find `_params_init_info` in {module}'
for name, param in module.named_parameters():
assert param in module._params_init_info, (
f'Find a new :obj:`Parameter` '
f'named `{name}` during executing the '
f'`init_weights` of '
f'`{module.__class__.__name__}`. '
f'Please do not add or '
f'replace parameters during executing '
f'the `init_weights`. ')
# The parameter has been changed during executing the
# `init_weights` of module
mean_value = param.data.mean().cpu()
if module._params_init_info[param]['tmp_mean_value'] != mean_value:
module._params_init_info[param]['init_info'] = init_info
module._params_init_info[param]['tmp_mean_value'] = mean_value
[docs]def constant_init(module, val, bias=0):
if hasattr(module, 'weight') and module.weight is not None:
nn.init.constant_(module.weight, val)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
[docs]def xavier_init(module, gain=1, bias=0, distribution='normal'):
assert distribution in ['uniform', 'normal']
if hasattr(module, 'weight') and module.weight is not None:
if distribution == 'uniform':
nn.init.xavier_uniform_(module.weight, gain=gain)
else:
nn.init.xavier_normal_(module.weight, gain=gain)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
[docs]def normal_init(module, mean=0, std=1, bias=0):
if hasattr(module, 'weight') and module.weight is not None:
nn.init.normal_(module.weight, mean, std)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
[docs]def trunc_normal_init(module: nn.Module,
mean: float = 0,
std: float = 1,
a: float = -2,
b: float = 2,
bias: float = 0) -> None:
if hasattr(module, 'weight') and module.weight is not None:
trunc_normal_(module.weight, mean, std, a, b) # type: ignore
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias) # type: ignore
[docs]def uniform_init(module, a=0, b=1, bias=0):
if hasattr(module, 'weight') and module.weight is not None:
nn.init.uniform_(module.weight, a, b)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
[docs]def kaiming_init(module,
a=0,
mode='fan_out',
nonlinearity='relu',
bias=0,
distribution='normal'):
assert distribution in ['uniform', 'normal']
if hasattr(module, 'weight') and module.weight is not None:
if distribution == 'uniform':
nn.init.kaiming_uniform_(
module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
else:
nn.init.kaiming_normal_(
module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
if hasattr(module, 'bias') and module.bias is not None:
nn.init.constant_(module.bias, bias)
[docs]def caffe2_xavier_init(module, bias=0):
# `XavierFill` in Caffe2 corresponds to `kaiming_uniform_` in PyTorch
# Acknowledgment to FAIR's internal code
kaiming_init(
module,
a=1,
mode='fan_in',
nonlinearity='leaky_relu',
bias=bias,
distribution='uniform')
[docs]def bias_init_with_prob(prior_prob):
"""initialize conv/fc bias value according to a given probability value."""
bias_init = float(-np.log((1 - prior_prob) / prior_prob))
return bias_init
def _get_bases_name(m):
return [b.__name__ for b in m.__class__.__bases__]
[docs]class BaseInit:
def __init__(self, *, bias=0, bias_prob=None, layer=None):
self.wholemodule = False
if not isinstance(bias, (int, float)):
raise TypeError(f'bias must be a number, but got a {type(bias)}')
if bias_prob is not None:
if not isinstance(bias_prob, float):
raise TypeError(f'bias_prob type must be float, \
but got {type(bias_prob)}')
if layer is not None:
if not isinstance(layer, (str, list)):
raise TypeError(f'layer must be a str or a list of str, \
but got a {type(layer)}')
else:
layer = []
if bias_prob is not None:
self.bias = bias_init_with_prob(bias_prob)
else:
self.bias = bias
self.layer = [layer] if isinstance(layer, str) else layer
def _get_init_info(self):
info = f'{self.__class__.__name__}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Constant')
class ConstantInit(BaseInit):
"""Initialize module parameters with constant values.
Args:
val (int | float): the value to fill the weights in the module with
bias (int | float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self, val, **kwargs):
super().__init__(**kwargs)
self.val = val
def __call__(self, module):
def init(m):
if self.wholemodule:
constant_init(m, self.val, self.bias)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
constant_init(m, self.val, self.bias)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: val={self.val}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Xavier')
class XavierInit(BaseInit):
r"""Initialize module parameters with values according to the method
described in `Understanding the difficulty of training deep feedforward
neural networks - Glorot, X. & Bengio, Y. (2010).
<http://proceedings.mlr.press/v9/glorot10a/glorot10a.pdf>`_
Args:
gain (int | float): an optional scaling factor. Defaults to 1.
bias (int | float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
distribution (str): distribution either be ``'normal'``
or ``'uniform'``. Defaults to ``'normal'``.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self, gain=1, distribution='normal', **kwargs):
super().__init__(**kwargs)
self.gain = gain
self.distribution = distribution
def __call__(self, module):
def init(m):
if self.wholemodule:
xavier_init(m, self.gain, self.bias, self.distribution)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
xavier_init(m, self.gain, self.bias, self.distribution)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: gain={self.gain}, ' \
f'distribution={self.distribution}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Normal')
class NormalInit(BaseInit):
r"""Initialize module parameters with the values drawn from the normal
distribution :math:`\mathcal{N}(\text{mean}, \text{std}^2)`.
Args:
mean (int | float):the mean of the normal distribution. Defaults to 0.
std (int | float): the standard deviation of the normal distribution.
Defaults to 1.
bias (int | float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self, mean=0, std=1, **kwargs):
super().__init__(**kwargs)
self.mean = mean
self.std = std
def __call__(self, module):
def init(m):
if self.wholemodule:
normal_init(m, self.mean, self.std, self.bias)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
normal_init(m, self.mean, self.std, self.bias)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: mean={self.mean},' \
f' std={self.std}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='TruncNormal')
class TruncNormalInit(BaseInit):
r"""Initialize module parameters with the values drawn from the normal
distribution :math:`\mathcal{N}(\text{mean}, \text{std}^2)` with values
outside :math:`[a, b]`.
Args:
mean (float): the mean of the normal distribution. Defaults to 0.
std (float): the standard deviation of the normal distribution.
Defaults to 1.
a (float): The minimum cutoff value.
b ( float): The maximum cutoff value.
bias (float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self,
mean: float = 0,
std: float = 1,
a: float = -2,
b: float = 2,
**kwargs) -> None:
super().__init__(**kwargs)
self.mean = mean
self.std = std
self.a = a
self.b = b
def __call__(self, module: nn.Module) -> None:
def init(m):
if self.wholemodule:
trunc_normal_init(m, self.mean, self.std, self.a, self.b,
self.bias)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
trunc_normal_init(m, self.mean, self.std, self.a, self.b,
self.bias)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: a={self.a}, b={self.b},' \
f' mean={self.mean}, std={self.std}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Uniform')
class UniformInit(BaseInit):
r"""Initialize module parameters with values drawn from the uniform
distribution :math:`\mathcal{U}(a, b)`.
Args:
a (int | float): the lower bound of the uniform distribution.
Defaults to 0.
b (int | float): the upper bound of the uniform distribution.
Defaults to 1.
bias (int | float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self, a=0, b=1, **kwargs):
super().__init__(**kwargs)
self.a = a
self.b = b
def __call__(self, module):
def init(m):
if self.wholemodule:
uniform_init(m, self.a, self.b, self.bias)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
uniform_init(m, self.a, self.b, self.bias)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: a={self.a},' \
f' b={self.b}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Kaiming')
class KaimingInit(BaseInit):
r"""Initialize module parameters with the values according to the method
described in `Delving deep into rectifiers: Surpassing human-level
performance on ImageNet classification - He, K. et al. (2015).
<https://www.cv-foundation.org/openaccess/content_iccv_2015/
papers/He_Delving_Deep_into_ICCV_2015_paper.pdf>`_
Args:
a (int | float): the negative slope of the rectifier used after this
layer (only used with ``'leaky_relu'``). Defaults to 0.
mode (str): either ``'fan_in'`` 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. Defaults to ``'fan_out'``.
nonlinearity (str): the non-linear function (`nn.functional` name),
recommended to use only with ``'relu'`` or ``'leaky_relu'`` .
Defaults to 'relu'.
bias (int | float): the value to fill the bias. Defaults to 0.
bias_prob (float, optional): the probability for bias initialization.
Defaults to None.
distribution (str): distribution either be ``'normal'`` or
``'uniform'``. Defaults to ``'normal'``.
layer (str | list[str], optional): the layer will be initialized.
Defaults to None.
"""
def __init__(self,
a=0,
mode='fan_out',
nonlinearity='relu',
distribution='normal',
**kwargs):
super().__init__(**kwargs)
self.a = a
self.mode = mode
self.nonlinearity = nonlinearity
self.distribution = distribution
def __call__(self, module):
def init(m):
if self.wholemodule:
kaiming_init(m, self.a, self.mode, self.nonlinearity,
self.bias, self.distribution)
else:
layername = m.__class__.__name__
basesname = _get_bases_name(m)
if len(set(self.layer) & set([layername] + basesname)):
kaiming_init(m, self.a, self.mode, self.nonlinearity,
self.bias, self.distribution)
module.apply(init)
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: a={self.a}, mode={self.mode}, ' \
f'nonlinearity={self.nonlinearity}, ' \
f'distribution ={self.distribution}, bias={self.bias}'
return info
[docs]@WEIGHT_INITIALIZERS.register_module(name='Caffe2Xavier')
class Caffe2XavierInit(KaimingInit):
# `XavierFill` in Caffe2 corresponds to `kaiming_uniform_` in PyTorch
# Acknowledgment to FAIR's internal code
def __init__(self, **kwargs):
super().__init__(
a=1,
mode='fan_in',
nonlinearity='leaky_relu',
distribution='uniform',
**kwargs)
def __call__(self, module):
super().__call__(module)
[docs]@WEIGHT_INITIALIZERS.register_module(name='Pretrained')
class PretrainedInit:
"""Initialize module by loading a pretrained model.
Args:
checkpoint (str): the checkpoint file of the pretrained model should
be load.
prefix (str, optional): the prefix of a sub-module in the pretrained
model. it is for loading a part of the pretrained model to
initialize. For example, if we would like to only load the
backbone of a detector model, we can set ``prefix='backbone.'``.
Defaults to None.
map_location (str): map tensors into proper locations. Defaults to cpu.
"""
def __init__(self, checkpoint, prefix=None, map_location='cpu'):
self.checkpoint = checkpoint
self.prefix = prefix
self.map_location = map_location
def __call__(self, module):
from mmengine.runner.checkpoint import (_load_checkpoint_with_prefix,
load_checkpoint,
load_state_dict)
if self.prefix is None:
print_log(f'load model from: {self.checkpoint}', logger='current')
load_checkpoint(
module,
self.checkpoint,
map_location=self.map_location,
strict=False,
logger='current')
else:
print_log(
f'load {self.prefix} in model from: {self.checkpoint}',
logger='current')
state_dict = _load_checkpoint_with_prefix(
self.prefix, self.checkpoint, map_location=self.map_location)
load_state_dict(module, state_dict, strict=False, logger='current')
if hasattr(module, '_params_init_info'):
update_init_info(module, init_info=self._get_init_info())
def _get_init_info(self):
info = f'{self.__class__.__name__}: load from {self.checkpoint}'
return info
def _initialize(module, cfg, wholemodule=False):
func = build_from_cfg(cfg, WEIGHT_INITIALIZERS)
# wholemodule flag is for override mode, there is no layer key in override
# and initializer will give init values for the whole module with the name
# in override.
func.wholemodule = wholemodule
func(module)
def _initialize_override(module, override, cfg):
if not isinstance(override, (dict, list)):
raise TypeError(f'override must be a dict or a list of dict, \
but got {type(override)}')
override = [override] if isinstance(override, dict) else override
for override_ in override:
cp_override = copy.deepcopy(override_)
name = cp_override.pop('name', None)
if name is None:
raise ValueError('`override` must contain the key "name",'
f'but got {cp_override}')
# if override only has name key, it means use args in init_cfg
if not cp_override:
cp_override.update(cfg)
# if override has name key and other args except type key, it will
# raise error
elif 'type' not in cp_override.keys():
raise ValueError(
f'`override` need "type" key, but got {cp_override}')
if hasattr(module, name):
_initialize(getattr(module, name), cp_override, wholemodule=True)
else:
raise RuntimeError(f'module did not have attribute {name}, '
f'but init_cfg is {cp_override}.')
[docs]def initialize(module, init_cfg):
r"""Initialize a module.
Args:
module (``torch.nn.Module``): the module will be initialized.
init_cfg (dict | list[dict]): initialization configuration dict to
define initializer. OpenMMLab has implemented 6 initializers
including ``Constant``, ``Xavier``, ``Normal``, ``Uniform``,
``Kaiming``, and ``Pretrained``.
Example:
>>> module = nn.Linear(2, 3, bias=True)
>>> init_cfg = dict(type='Constant', layer='Linear', val =1 , bias =2)
>>> initialize(module, init_cfg)
>>> module = nn.Sequential(nn.Conv1d(3, 1, 3), nn.Linear(1,2))
>>> # define key ``'layer'`` for initializing layer with different
>>> # configuration
>>> init_cfg = [dict(type='Constant', layer='Conv1d', val=1),
dict(type='Constant', layer='Linear', val=2)]
>>> initialize(module, init_cfg)
>>> # define key``'override'`` to initialize some specific part in
>>> # module
>>> class FooNet(nn.Module):
>>> def __init__(self):
>>> super().__init__()
>>> self.feat = nn.Conv2d(3, 16, 3)
>>> self.reg = nn.Conv2d(16, 10, 3)
>>> self.cls = nn.Conv2d(16, 5, 3)
>>> model = FooNet()
>>> init_cfg = dict(type='Constant', val=1, bias=2, layer='Conv2d',
>>> override=dict(type='Constant', name='reg', val=3, bias=4))
>>> initialize(model, init_cfg)
>>> model = ResNet(depth=50)
>>> # Initialize weights with the pretrained model.
>>> init_cfg = dict(type='Pretrained',
checkpoint='torchvision://resnet50')
>>> initialize(model, init_cfg)
>>> # Initialize weights of a sub-module with the specific part of
>>> # a pretrained model by using "prefix".
>>> url = 'http://download.openmmlab.com/mmdetection/v2.0/retinanet/'\
>>> 'retinanet_r50_fpn_1x_coco/'\
>>> 'retinanet_r50_fpn_1x_coco_20200130-c2398f9e.pth'
>>> init_cfg = dict(type='Pretrained',
checkpoint=url, prefix='backbone.')
"""
if not isinstance(init_cfg, (dict, list)):
raise TypeError(f'init_cfg must be a dict or a list of dict, \
but got {type(init_cfg)}')
if isinstance(init_cfg, dict):
init_cfg = [init_cfg]
for cfg in init_cfg:
# should deeply copy the original config because cfg may be used by
# other modules, e.g., one init_cfg shared by multiple bottleneck
# blocks, the expected cfg will be changed after pop and will change
# the initialization behavior of other modules
cp_cfg = copy.deepcopy(cfg)
override = cp_cfg.pop('override', None)
_initialize(module, cp_cfg)
if override is not None:
cp_cfg.pop('layer', None)
_initialize_override(module, override, cp_cfg)
else:
# All attributes in module have same initialization.
pass
def _no_grad_trunc_normal_(tensor: Tensor, mean: float, std: float, a: float,
b: float) -> Tensor:
# Method based on
# https://people.sc.fsu.edu/~jburkardt/presentations/truncated_normal.pdf
# Modified from
# https://github.com/pytorch/pytorch/blob/master/torch/nn/init.py
def norm_cdf(x):
# Computes standard normal cumulative distribution function
return (1. + math.erf(x / math.sqrt(2.))) / 2.
if (mean < a - 2 * std) or (mean > b + 2 * std):
warnings.warn(
'mean is more than 2 std from [a, b] in nn.init.trunc_normal_. '
'The distribution of values may be incorrect.',
stacklevel=2)
with torch.no_grad():
# Values are generated by using a truncated uniform distribution and
# then using the inverse CDF for the normal distribution.
# Get upper and lower cdf values
lower = norm_cdf((a - mean) / std)
upper = norm_cdf((b - mean) / std)
# Uniformly fill tensor with values from [lower, upper], then translate
# to [2lower-1, 2upper-1].
tensor.uniform_(2 * lower - 1, 2 * upper - 1)
# Use inverse cdf transform for normal distribution to get truncated
# standard normal
tensor.erfinv_()
# Transform to proper mean, std
tensor.mul_(std * math.sqrt(2.))
tensor.add_(mean)
# Clamp to ensure it's in the proper range
tensor.clamp_(min=a, max=b)
return tensor
def trunc_normal_(tensor: Tensor,
mean: float = 0.,
std: float = 1.,
a: float = -2.,
b: float = 2.) -> Tensor:
r"""Fills the input Tensor with values drawn from a truncated
normal distribution. The values are effectively drawn from the
normal distribution :math:`\mathcal{N}(\text{mean}, \text{std}^2)`
with values outside :math:`[a, b]` redrawn until they are within
the bounds. The method used for generating the random values works
best when :math:`a \leq \text{mean} \leq b`.
Modified from
https://github.com/pytorch/pytorch/blob/master/torch/nn/init.py
Args:
tensor (``torch.Tensor``): an n-dimensional `torch.Tensor`.
mean (float): the mean of the normal distribution.
std (float): the standard deviation of the normal distribution.
a (float): the minimum cutoff value.
b (float): the maximum cutoff value.
"""
return _no_grad_trunc_normal_(tensor, mean, std, a, b)