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Source code for mmcv.runner.optimizer.default_constructor

# Copyright (c) OpenMMLab. All rights reserved.
import warnings
from typing import Dict, List, Optional, Union

import torch
import torch.nn as nn
from torch.nn import GroupNorm, LayerNorm

from mmcv.utils import _BatchNorm, _InstanceNorm, build_from_cfg, is_list_of
from mmcv.utils.ext_loader import check_ops_exist
from .builder import OPTIMIZER_BUILDERS, OPTIMIZERS


[docs]@OPTIMIZER_BUILDERS.register_module() class DefaultOptimizerConstructor: """Default constructor for optimizers. By default each parameter share the same optimizer settings, and we provide an argument ``paramwise_cfg`` to specify parameter-wise settings. It is a dict and may contain the following fields: - ``custom_keys`` (dict): Specified parameters-wise settings by keys. If one of the keys in ``custom_keys`` is a substring of the name of one parameter, then the setting of the parameter will be specified by ``custom_keys[key]`` and other setting like ``bias_lr_mult`` etc. will be ignored. It should be noted that the aforementioned ``key`` is the longest key that is a substring of the name of the parameter. If there are multiple matched keys with the same length, then the key with lower alphabet order will be chosen. ``custom_keys[key]`` should be a dict and may contain fields ``lr_mult`` and ``decay_mult``. See Example 2 below. - ``bias_lr_mult`` (float): It will be multiplied to the learning rate for all bias parameters (except for those in normalization layers and offset layers of DCN). - ``bias_decay_mult`` (float): It will be multiplied to the weight decay for all bias parameters (except for those in normalization layers, depthwise conv layers, offset layers of DCN). - ``norm_decay_mult`` (float): It will be multiplied to the weight decay for all weight and bias parameters of normalization layers. - ``dwconv_decay_mult`` (float): It will be multiplied to the weight decay for all weight and bias parameters of depthwise conv layers. - ``dcn_offset_lr_mult`` (float): It will be multiplied to the learning rate for parameters of offset layer in the deformable convs of a model. - ``bypass_duplicate`` (bool): If true, the duplicate parameters would not be added into optimizer. Default: False. Note: 1. If the option ``dcn_offset_lr_mult`` is used, the constructor will override the effect of ``bias_lr_mult`` in the bias of offset layer. So be careful when using both ``bias_lr_mult`` and ``dcn_offset_lr_mult``. If you wish to apply both of them to the offset layer in deformable convs, set ``dcn_offset_lr_mult`` to the original ``dcn_offset_lr_mult`` * ``bias_lr_mult``. 2. If the option ``dcn_offset_lr_mult`` is used, the constructor will apply it to all the DCN layers in the model. So be careful when the model contains multiple DCN layers in places other than backbone. Args: model (:obj:`nn.Module`): The model with parameters to be optimized. optimizer_cfg (dict): The config dict of the optimizer. Positional fields are - `type`: class name of the optimizer. Optional fields are - any arguments of the corresponding optimizer type, e.g., lr, weight_decay, momentum, etc. paramwise_cfg (dict, optional): Parameter-wise options. Example 1: >>> model = torch.nn.modules.Conv1d(1, 1, 1) >>> optimizer_cfg = dict(type='SGD', lr=0.01, momentum=0.9, >>> weight_decay=0.0001) >>> paramwise_cfg = dict(norm_decay_mult=0.) >>> optim_builder = DefaultOptimizerConstructor( >>> optimizer_cfg, paramwise_cfg) >>> optimizer = optim_builder(model) Example 2: >>> # assume model have attribute model.backbone and model.cls_head >>> optimizer_cfg = dict(type='SGD', lr=0.01, weight_decay=0.95) >>> paramwise_cfg = dict(custom_keys={ 'backbone': dict(lr_mult=0.1, decay_mult=0.9)}) >>> optim_builder = DefaultOptimizerConstructor( >>> optimizer_cfg, paramwise_cfg) >>> optimizer = optim_builder(model) >>> # Then the `lr` and `weight_decay` for model.backbone is >>> # (0.01 * 0.1, 0.95 * 0.9). `lr` and `weight_decay` for >>> # model.cls_head is (0.01, 0.95). """ def __init__(self, optimizer_cfg: Dict, paramwise_cfg: Optional[Dict] = None): if not isinstance(optimizer_cfg, dict): raise TypeError('optimizer_cfg should be a dict', f'but got {type(optimizer_cfg)}') self.optimizer_cfg = optimizer_cfg self.paramwise_cfg = {} if paramwise_cfg is None else paramwise_cfg self.base_lr = optimizer_cfg.get('lr', None) self.base_wd = optimizer_cfg.get('weight_decay', None) self._validate_cfg() def _validate_cfg(self) -> None: if not isinstance(self.paramwise_cfg, dict): raise TypeError('paramwise_cfg should be None or a dict, ' f'but got {type(self.paramwise_cfg)}') if 'custom_keys' in self.paramwise_cfg: if not isinstance(self.paramwise_cfg['custom_keys'], dict): raise TypeError( 'If specified, custom_keys must be a dict, ' f'but got {type(self.paramwise_cfg["custom_keys"])}') if self.base_wd is None: for key in self.paramwise_cfg['custom_keys']: if 'decay_mult' in self.paramwise_cfg['custom_keys'][key]: raise ValueError('base_wd should not be None') # get base lr and weight decay # weight_decay must be explicitly specified if mult is specified if ('bias_decay_mult' in self.paramwise_cfg or 'norm_decay_mult' in self.paramwise_cfg or 'dwconv_decay_mult' in self.paramwise_cfg): if self.base_wd is None: raise ValueError('base_wd should not be None') def _is_in(self, param_group: Dict, param_group_list: List) -> bool: assert is_list_of(param_group_list, dict) param = set(param_group['params']) param_set = set() for group in param_group_list: param_set.update(set(group['params'])) return not param.isdisjoint(param_set)
[docs] def add_params(self, params: List[Dict], module: nn.Module, prefix: str = '', is_dcn_module: Union[int, float, None] = None) -> None: """Add all parameters of module to the params list. The parameters of the given module will be added to the list of param groups, with specific rules defined by paramwise_cfg. Args: params (list[dict]): A list of param groups, it will be modified in place. module (nn.Module): The module to be added. prefix (str): The prefix of the module is_dcn_module (int|float|None): If the current module is a submodule of DCN, `is_dcn_module` will be passed to control conv_offset layer's learning rate. Defaults to None. """ # get param-wise options custom_keys = self.paramwise_cfg.get('custom_keys', {}) # first sort with alphabet order and then sort with reversed len of str sorted_keys = sorted(sorted(custom_keys.keys()), key=len, reverse=True) bias_lr_mult = self.paramwise_cfg.get('bias_lr_mult', 1.) bias_decay_mult = self.paramwise_cfg.get('bias_decay_mult', 1.) norm_decay_mult = self.paramwise_cfg.get('norm_decay_mult', 1.) dwconv_decay_mult = self.paramwise_cfg.get('dwconv_decay_mult', 1.) bypass_duplicate = self.paramwise_cfg.get('bypass_duplicate', False) dcn_offset_lr_mult = self.paramwise_cfg.get('dcn_offset_lr_mult', 1.) # special rules for norm layers and depth-wise conv layers is_norm = isinstance(module, (_BatchNorm, _InstanceNorm, GroupNorm, LayerNorm)) is_dwconv = ( isinstance(module, torch.nn.Conv2d) and module.in_channels == module.groups) for name, param in module.named_parameters(recurse=False): param_group = {'params': [param]} if not param.requires_grad: params.append(param_group) continue if bypass_duplicate and self._is_in(param_group, params): warnings.warn(f'{prefix} is duplicate. It is skipped since ' f'bypass_duplicate={bypass_duplicate}') continue # if the parameter match one of the custom keys, ignore other rules is_custom = False for key in sorted_keys: if key in f'{prefix}.{name}': is_custom = True lr_mult = custom_keys[key].get('lr_mult', 1.) param_group['lr'] = self.base_lr * lr_mult if self.base_wd is not None: decay_mult = custom_keys[key].get('decay_mult', 1.) param_group['weight_decay'] = self.base_wd * decay_mult break if not is_custom: # bias_lr_mult affects all bias parameters # except for norm.bias dcn.conv_offset.bias if name == 'bias' and not (is_norm or is_dcn_module): param_group['lr'] = self.base_lr * bias_lr_mult if (prefix.find('conv_offset') != -1 and is_dcn_module and isinstance(module, torch.nn.Conv2d)): # deal with both dcn_offset's bias & weight param_group['lr'] = self.base_lr * dcn_offset_lr_mult # apply weight decay policies if self.base_wd is not None: # norm decay if is_norm: param_group[ 'weight_decay'] = self.base_wd * norm_decay_mult # depth-wise conv elif is_dwconv: param_group[ 'weight_decay'] = self.base_wd * dwconv_decay_mult # bias lr and decay elif name == 'bias' and not is_dcn_module: # TODO: current bias_decay_mult will have affect on DCN param_group[ 'weight_decay'] = self.base_wd * bias_decay_mult params.append(param_group) if check_ops_exist(): from mmcv.ops import DeformConv2d, ModulatedDeformConv2d is_dcn_module = isinstance(module, (DeformConv2d, ModulatedDeformConv2d)) else: is_dcn_module = False for child_name, child_mod in module.named_children(): child_prefix = f'{prefix}.{child_name}' if prefix else child_name self.add_params( params, child_mod, prefix=child_prefix, is_dcn_module=is_dcn_module)
def __call__(self, model: nn.Module): if hasattr(model, 'module'): model = model.module optimizer_cfg = self.optimizer_cfg.copy() # if no paramwise option is specified, just use the global setting if not self.paramwise_cfg: optimizer_cfg['params'] = model.parameters() return build_from_cfg(optimizer_cfg, OPTIMIZERS) # set param-wise lr and weight decay recursively params: List[Dict] = [] self.add_params(params, model) optimizer_cfg['params'] = params return build_from_cfg(optimizer_cfg, OPTIMIZERS)
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