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# This file is modified from https://github.com/traveller59/second.pytorch
try:
from collections.abc import Iterable
except:
from collections import Iterable
import torch
from torch import nn
from torch._utils import _unflatten_dense_tensors
from torch.nn.utils import parameters_to_vector
bn_types = (nn.BatchNorm1d, nn.BatchNorm2d, nn.BatchNorm3d, nn.SyncBatchNorm)
def split_bn_bias(layer_groups):
"Split the layers in `layer_groups` into batchnorm (`bn_types`) and non-batchnorm groups."
split_groups = []
for l in layer_groups:
l1, l2 = [], []
for c in l.children():
if isinstance(c, bn_types):
l2.append(c)
else:
l1.append(c)
split_groups += [nn.Sequential(*l1), nn.Sequential(*l2)]
return split_groups
def get_master(layer_groups, flat_master: bool = False):
"Return two lists, one for the model parameters in FP16 and one for the master parameters in FP32."
split_groups = split_bn_bias(layer_groups)
model_params = [[param for param in lg.parameters() if param.requires_grad] for lg in split_groups]
if flat_master:
master_params = []
for lg in model_params:
if len(lg) != 0:
mp = parameters_to_vector([param.data.float() for param in lg])
mp = torch.nn.Parameter(mp, requires_grad=True)
if mp.grad is None: mp.grad = mp.new(*mp.size())
master_params.append([mp])
else:
master_params.append([])
return model_params, master_params
else:
master_params = [[param.clone().float().detach() for param in lg] for lg in model_params]
for mp in master_params:
for param in mp: param.requires_grad = True
return model_params, master_params
def model_g2master_g(model_params, master_params, flat_master: bool = False) -> None:
"Copy the `model_params` gradients to `master_params` for the optimizer step."
if flat_master:
for model_group, master_group in zip(model_params, master_params):
if len(master_group) != 0:
master_group[0].grad.data.copy_(parameters_to_vector([p.grad.data.float() for p in model_group]))
else:
for model_group, master_group in zip(model_params, master_params):
for model, master in zip(model_group, master_group):
if model.grad is not None:
if master.grad is None: master.grad = master.data.new(*master.data.size())
master.grad.data.copy_(model.grad.data)
else:
master.grad = None
def master2model(model_params, master_params, flat_master: bool = False) -> None:
"Copy `master_params` to `model_params`."
if flat_master:
for model_group, master_group in zip(model_params, master_params):
if len(model_group) != 0:
for model, master in zip(model_group, _unflatten_dense_tensors(master_group[0].data, model_group)):
model.data.copy_(master)
else:
for model_group, master_group in zip(model_params, master_params):
for model, master in zip(model_group, master_group): model.data.copy_(master.data)
def listify(p=None, q=None):
"Make `p` listy and the same length as `q`."
if p is None:
p = []
elif isinstance(p, str):
p = [p]
elif not isinstance(p, Iterable):
p = [p]
n = q if type(q) == int else len(p) if q is None else len(q)
if len(p) == 1: p = p * n
assert len(p) == n, f'List len mismatch ({len(p)} vs {n})'
return list(p)
def trainable_params(m: nn.Module):
"Return list of trainable params in `m`."
res = filter(lambda p: p.requires_grad, m.parameters())
return res
def is_tuple(x) -> bool: return isinstance(x, tuple)
# copy from fastai.
class OptimWrapper():
"Basic wrapper around `opt` to simplify hyper-parameters changes."
def __init__(self, opt, wd, true_wd: bool = False, bn_wd: bool = True):
self.opt, self.true_wd, self.bn_wd = opt, true_wd, bn_wd
self.opt_keys = list(self.opt.param_groups[0].keys())
self.opt_keys.remove('params')
self.read_defaults()
self.wd = wd
@classmethod
def create(cls, opt_func, lr,
layer_groups, **kwargs):
"Create an `optim.Optimizer` from `opt_func` with `lr`. Set lr on `layer_groups`."
split_groups = split_bn_bias(layer_groups)
opt = opt_func([{'params': trainable_params(l), 'lr': 0} for l in split_groups])
opt = cls(opt, **kwargs)
opt.lr, opt.opt_func = listify(lr, layer_groups), opt_func
return opt
def new(self, layer_groups):
"Create a new `OptimWrapper` from `self` with another `layer_groups` but the same hyper-parameters."
opt_func = getattr(self, 'opt_func', self.opt.__class__)
split_groups = split_bn_bias(layer_groups)
opt = opt_func([{'params': trainable_params(l), 'lr': 0} for l in split_groups])
return self.create(opt_func, self.lr, layer_groups, wd=self.wd, true_wd=self.true_wd, bn_wd=self.bn_wd)
def __repr__(self) -> str:
return f'OptimWrapper over {repr(self.opt)}.\nTrue weight decay: {self.true_wd}'
# Pytorch optimizer methods
def step(self) -> None:
"Set weight decay and step optimizer."
# weight decay outside of optimizer step (AdamW)
if self.true_wd:
for lr, wd, pg1, pg2 in zip(self._lr, self._wd, self.opt.param_groups[::2], self.opt.param_groups[1::2]):
for p in pg1['params']:
# When some parameters are fixed: Shaoshuai Shi
if p.requires_grad is False:
continue
p.data.mul_(1 - wd * lr)
if self.bn_wd:
for p in pg2['params']:
# When some parameters are fixed: Shaoshuai Shi
if p.requires_grad is False:
continue
p.data.mul_(1 - wd * lr)
self.set_val('weight_decay', listify(0, self._wd))
self.opt.step()
def zero_grad(self) -> None:
"Clear optimizer gradients."
self.opt.zero_grad()
# Passthrough to the inner opt.
def __getattr__(self, k: str):
return getattr(self.opt, k, None)
def clear(self):
"Reset the state of the inner optimizer."
sd = self.state_dict()
sd['state'] = {}
self.load_state_dict(sd)
# Hyperparameters as properties
@property
def lr(self) -> float:
return self._lr[-1]
@lr.setter
def lr(self, val: float) -> None:
self._lr = self.set_val('lr', listify(val, self._lr))
@property
def mom(self) -> float:
return self._mom[-1]
@mom.setter
def mom(self, val: float) -> None:
if 'momentum' in self.opt_keys:
self.set_val('momentum', listify(val, self._mom))
elif 'betas' in self.opt_keys:
self.set_val('betas', (listify(val, self._mom), self._beta))
self._mom = listify(val, self._mom)
@property
def beta(self) -> float:
return None if self._beta is None else self._beta[-1]
@beta.setter
def beta(self, val: float) -> None:
"Set beta (or alpha as makes sense for given optimizer)."
if val is None: return
if 'betas' in self.opt_keys:
self.set_val('betas', (self._mom, listify(val, self._beta)))
elif 'alpha' in self.opt_keys:
self.set_val('alpha', listify(val, self._beta))
self._beta = listify(val, self._beta)
@property
def wd(self) -> float:
return self._wd[-1]
@wd.setter
def wd(self, val: float) -> None:
"Set weight decay."
if not self.true_wd: self.set_val('weight_decay', listify(val, self._wd), bn_groups=self.bn_wd)
self._wd = listify(val, self._wd)
# Helper functions
def read_defaults(self) -> None:
"Read the values inside the optimizer for the hyper-parameters."
self._beta = None
if 'lr' in self.opt_keys: self._lr = self.read_val('lr')
if 'momentum' in self.opt_keys: self._mom = self.read_val('momentum')
if 'alpha' in self.opt_keys: self._beta = self.read_val('alpha')
if 'betas' in self.opt_keys: self._mom, self._beta = self.read_val('betas')
if 'weight_decay' in self.opt_keys: self._wd = self.read_val('weight_decay')
def set_val(self, key: str, val, bn_groups: bool = True):
"Set `val` inside the optimizer dictionary at `key`."
if is_tuple(val): val = [(v1, v2) for v1, v2 in zip(*val)]
for v, pg1, pg2 in zip(val, self.opt.param_groups[::2], self.opt.param_groups[1::2]):
pg1[key] = v
if bn_groups: pg2[key] = v
return val
def read_val(self, key: str):
"Read a hyperparameter `key` in the optimizer dictionary."
val = [pg[key] for pg in self.opt.param_groups[::2]]
if is_tuple(val[0]): val = [o[0] for o in val], [o[1] for o in val]
return val
class FastAIMixedOptim(OptimWrapper):
@classmethod
def create(cls, opt_func, lr,
layer_groups, model, flat_master=False, loss_scale=512.0, **kwargs):
"Create an `optim.Optimizer` from `opt_func` with `lr`. Set lr on `layer_groups`."
opt = OptimWrapper.create(opt_func, lr, layer_groups, **kwargs)
opt.model_params, opt.master_params = get_master(layer_groups, flat_master)
opt.flat_master = flat_master
opt.loss_scale = loss_scale
opt.model = model
# Changes the optimizer so that the optimization step is done in FP32.
# opt = self.learn.opt
mom, wd, beta = opt.mom, opt.wd, opt.beta
lrs = [lr for lr in opt._lr for _ in range(2)]
opt_params = [{'params': mp, 'lr': lr} for mp, lr in zip(opt.master_params, lrs)]
opt.opt = opt_func(opt_params)
opt.mom, opt.wd, opt.beta = mom, wd, beta
return opt
def step(self):
model_g2master_g(self.model_params, self.master_params, self.flat_master)
for group in self.master_params:
for param in group: param.grad.div_(self.loss_scale)
super(FastAIMixedOptim, self).step()
self.model.zero_grad()
# Update the params from master to model.
master2model(self.model_params, self.master_params, self.flat_master)
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