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import logging
from itertools import islice
from typing import Collection, Optional
from torch import nn as nn
from timm.models import group_parameters
_logger = logging.getLogger(__name__)
def param_groups_weight_decay(
model: nn.Module,
weight_decay: float = 1e-5,
no_weight_decay_list: Collection[str] = (),
):
no_weight_decay_list = set(no_weight_decay_list)
decay = []
no_decay = []
for name, param in model.named_parameters():
if not param.requires_grad:
continue
if param.ndim <= 1 or name.endswith(".bias") or name in no_weight_decay_list:
no_decay.append(param)
else:
decay.append(param)
return [
{'params': no_decay, 'weight_decay': 0.},
{'params': decay, 'weight_decay': weight_decay}]
def _group(it, size):
it = iter(it)
return iter(lambda: tuple(islice(it, size)), ())
def auto_group_layers(model, layers_per_group=12, num_groups=None):
def _in_head(n, hp):
if not hp:
return True
elif isinstance(hp, (tuple, list)):
return any([n.startswith(hpi) for hpi in hp])
else:
return n.startswith(hp)
head_prefix = getattr(model, 'pretrained_cfg', {}).get('classifier', None)
names_trunk = []
names_head = []
for n, _ in model.named_parameters():
names_head.append(n) if _in_head(n, head_prefix) else names_trunk.append(n)
# group non-head layers
num_trunk_layers = len(names_trunk)
if num_groups is not None:
layers_per_group = -(num_trunk_layers // -num_groups)
names_trunk = list(_group(names_trunk, layers_per_group))
num_trunk_groups = len(names_trunk)
layer_map = {n: i for i, l in enumerate(names_trunk) for n in l}
layer_map.update({n: num_trunk_groups for n in names_head})
return layer_map
_layer_map = auto_group_layers # backward compat
def param_groups_layer_decay(
model: nn.Module,
weight_decay: float = 0.05,
no_weight_decay_list: Collection[str] = (),
weight_decay_exclude_1d: bool = True,
layer_decay: float = .75,
end_layer_decay: Optional[float] = None,
verbose: bool = False,
):
"""
Parameter groups for layer-wise lr decay & weight decay
Based on BEiT: https://github.com/microsoft/unilm/blob/master/beit/optim_factory.py#L58
"""
no_weight_decay_list = set(no_weight_decay_list)
param_group_names = {} # NOTE for debugging
param_groups = {}
if hasattr(model, 'group_matcher'):
# FIXME interface needs more work
layer_map = group_parameters(model, model.group_matcher(coarse=False), reverse=True)
else:
# fallback
layer_map = auto_group_layers(model)
num_layers = max(layer_map.values()) + 1
layer_max = num_layers - 1
layer_scales = list(layer_decay ** (layer_max - i) for i in range(num_layers))
for name, param in model.named_parameters():
if not param.requires_grad:
continue
# no decay: all 1D parameters and model specific ones
if (weight_decay_exclude_1d and param.ndim <= 1) or name in no_weight_decay_list:
g_decay = "no_decay"
this_decay = 0.
else:
g_decay = "decay"
this_decay = weight_decay
layer_id = layer_map.get(name, layer_max)
group_name = "layer_%d_%s" % (layer_id, g_decay)
if group_name not in param_groups:
this_scale = layer_scales[layer_id]
param_group_names[group_name] = {
"lr_scale": this_scale,
"weight_decay": this_decay,
"param_names": [],
}
param_groups[group_name] = {
"lr_scale": this_scale,
"weight_decay": this_decay,
"params": [],
}
param_group_names[group_name]["param_names"].append(name)
param_groups[group_name]["params"].append(param)
if verbose:
import json
_logger.info("parameter groups: \n%s" % json.dumps(param_group_names, indent=2))
return list(param_groups.values())
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