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""" | ||
Helpers to train with 16-bit precision. | ||
""" | ||
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import numpy as np | ||
import torch as th | ||
import torch.nn as nn | ||
from torch._utils import _flatten_dense_tensors, _unflatten_dense_tensors | ||
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from diffusion import logger | ||
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INITIAL_LOG_LOSS_SCALE = 20.0 | ||
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def convert_module_to_f16(l): | ||
""" | ||
Convert primitive modules to float16. | ||
""" | ||
if isinstance(l, (nn.Conv1d, nn.Conv2d, nn.Conv3d)): | ||
l.weight.data = l.weight.data.half() | ||
if l.bias is not None: | ||
l.bias.data = l.bias.data.half() | ||
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def convert_module_to_f32(l): | ||
""" | ||
Convert primitive modules to float32, undoing convert_module_to_f16(). | ||
""" | ||
if isinstance(l, (nn.Conv1d, nn.Conv2d, nn.Conv3d)): | ||
l.weight.data = l.weight.data.float() | ||
if l.bias is not None: | ||
l.bias.data = l.bias.data.float() | ||
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def make_master_params(param_groups_and_shapes): | ||
""" | ||
Copy model parameters into a (differently-shaped) list of full-precision | ||
parameters. | ||
""" | ||
master_params = [] | ||
for param_group, shape in param_groups_and_shapes: | ||
master_param = nn.Parameter( | ||
_flatten_dense_tensors( | ||
[param.detach().float() for (_, param) in param_group] | ||
).view(shape) | ||
) | ||
master_param.requires_grad = True | ||
master_params.append(master_param) | ||
return master_params | ||
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def model_grads_to_master_grads(param_groups_and_shapes, master_params): | ||
""" | ||
Copy the gradients from the model parameters into the master parameters | ||
from make_master_params(). | ||
""" | ||
for master_param, (param_group, shape) in zip( | ||
master_params, param_groups_and_shapes | ||
): | ||
master_param.grad = _flatten_dense_tensors( | ||
[param_grad_or_zeros(param) for (_, param) in param_group] | ||
).view(shape) | ||
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def master_params_to_model_params(param_groups_and_shapes, master_params): | ||
""" | ||
Copy the master parameter data back into the model parameters. | ||
""" | ||
# Without copying to a list, if a generator is passed, this will | ||
# silently not copy any parameters. | ||
for master_param, (param_group, _) in zip(master_params, param_groups_and_shapes): | ||
for (_, param), unflat_master_param in zip( | ||
param_group, unflatten_master_params(param_group, master_param.view(-1)) | ||
): | ||
param.detach().copy_(unflat_master_param) | ||
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def unflatten_master_params(param_group, master_param): | ||
return _unflatten_dense_tensors(master_param, [param for (_, param) in param_group]) | ||
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def get_param_groups_and_shapes(named_model_params): | ||
named_model_params = list(named_model_params) | ||
scalar_vector_named_params = ( | ||
[(n, p) for (n, p) in named_model_params if p.ndim <= 1], | ||
(-1), | ||
) | ||
matrix_named_params = ( | ||
[(n, p) for (n, p) in named_model_params if p.ndim > 1], | ||
(1, -1), | ||
) | ||
return [scalar_vector_named_params, matrix_named_params] | ||
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def master_params_to_state_dict( | ||
model, param_groups_and_shapes, master_params, use_fp16 | ||
): | ||
if use_fp16: | ||
state_dict = model.state_dict() | ||
for master_param, (param_group, _) in zip( | ||
master_params, param_groups_and_shapes | ||
): | ||
for (name, _), unflat_master_param in zip( | ||
param_group, unflatten_master_params(param_group, master_param.view(-1)) | ||
): | ||
assert name in state_dict | ||
state_dict[name] = unflat_master_param | ||
else: | ||
state_dict = model.state_dict() | ||
for i, (name, _value) in enumerate(model.named_parameters()): | ||
assert name in state_dict | ||
state_dict[name] = master_params[i] | ||
return state_dict | ||
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def state_dict_to_master_params(model, state_dict, use_fp16): | ||
if use_fp16: | ||
named_model_params = [ | ||
(name, state_dict[name]) for name, _ in model.named_parameters() | ||
] | ||
param_groups_and_shapes = get_param_groups_and_shapes(named_model_params) | ||
master_params = make_master_params(param_groups_and_shapes) | ||
else: | ||
master_params = [state_dict[name] for name, _ in model.named_parameters()] | ||
return master_params | ||
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def zero_master_grads(master_params): | ||
for param in master_params: | ||
param.grad = None | ||
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def zero_grad(model_params): | ||
for param in model_params: | ||
# Taken from https://pytorch.org/docs/stable/_modules/torch/optim/optimizer.html#Optimizer.add_param_group | ||
if param.grad is not None: | ||
param.grad.detach_() | ||
param.grad.zero_() | ||
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def param_grad_or_zeros(param): | ||
if param.grad is not None: | ||
return param.grad.data.detach() | ||
else: | ||
return th.zeros_like(param) | ||
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class MixedPrecisionTrainer: | ||
def __init__( | ||
self, | ||
*, | ||
model, | ||
use_fp16=False, | ||
fp16_scale_growth=1e-3, | ||
initial_lg_loss_scale=INITIAL_LOG_LOSS_SCALE, | ||
): | ||
self.model = model | ||
self.use_fp16 = use_fp16 | ||
self.fp16_scale_growth = fp16_scale_growth | ||
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self.model_params = list(self.model.parameters()) | ||
self.master_params = self.model_params | ||
self.param_groups_and_shapes = None | ||
self.lg_loss_scale = initial_lg_loss_scale | ||
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if self.use_fp16: | ||
self.param_groups_and_shapes = get_param_groups_and_shapes( | ||
self.model.named_parameters() | ||
) | ||
self.master_params = make_master_params(self.param_groups_and_shapes) | ||
self.model.convert_to_fp16() | ||
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def zero_grad(self): | ||
zero_grad(self.model_params) | ||
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def backward(self, loss: th.Tensor): | ||
if self.use_fp16: | ||
loss_scale = 2 ** self.lg_loss_scale | ||
(loss * loss_scale).backward() | ||
else: | ||
loss.backward() | ||
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def optimize(self, opt: th.optim.Optimizer): | ||
if self.use_fp16: | ||
return self._optimize_fp16(opt) | ||
else: | ||
return self._optimize_normal(opt) | ||
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def _optimize_fp16(self, opt: th.optim.Optimizer): | ||
logger.logkv_mean("lg_loss_scale", self.lg_loss_scale) | ||
model_grads_to_master_grads(self.param_groups_and_shapes, self.master_params) | ||
grad_norm, param_norm = self._compute_norms(grad_scale=2 ** self.lg_loss_scale) | ||
if check_overflow(grad_norm): | ||
self.lg_loss_scale -= 1 | ||
logger.log(f"Found NaN, decreased lg_loss_scale to {self.lg_loss_scale}") | ||
zero_master_grads(self.master_params) | ||
return False | ||
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logger.logkv_mean("grad_norm", grad_norm) | ||
logger.logkv_mean("param_norm", param_norm) | ||
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self.master_params[0].grad.mul_(1.0 / (2 ** self.lg_loss_scale)) | ||
opt.step() | ||
zero_master_grads(self.master_params) | ||
master_params_to_model_params(self.param_groups_and_shapes, self.master_params) | ||
self.lg_loss_scale += self.fp16_scale_growth | ||
return True | ||
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def _optimize_normal(self, opt: th.optim.Optimizer): | ||
grad_norm, param_norm = self._compute_norms() | ||
logger.logkv_mean("grad_norm", grad_norm) | ||
logger.logkv_mean("param_norm", param_norm) | ||
opt.step() | ||
return True | ||
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def _compute_norms(self, grad_scale=1.0): | ||
grad_norm = 0.0 | ||
param_norm = 0.0 | ||
for p in self.master_params: | ||
with th.no_grad(): | ||
param_norm += th.norm(p, p=2, dtype=th.float32).item() ** 2 | ||
if p.grad is not None: | ||
grad_norm += th.norm(p.grad, p=2, dtype=th.float32).item() ** 2 | ||
return np.sqrt(grad_norm) / grad_scale, np.sqrt(param_norm) | ||
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def master_params_to_state_dict(self, master_params): | ||
return master_params_to_state_dict( | ||
self.model, self.param_groups_and_shapes, master_params, self.use_fp16 | ||
) | ||
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def state_dict_to_master_params(self, state_dict): | ||
return state_dict_to_master_params(self.model, state_dict, self.use_fp16) | ||
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def check_overflow(value): | ||
return (value == float("inf")) or (value == -float("inf")) or (value != value) |
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