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from typing import Optional, Union | |
import lightning.pytorch as pl | |
import torch | |
from lightning import LightningModule, Trainer | |
from lightning.pytorch.callbacks import Callback | |
from torch import Tensor, nn | |
from torch.utils._foreach_utils import ( | |
_group_tensors_by_device_and_dtype, | |
_has_foreach_support, | |
) | |
def grad_norm( | |
parameters: Union[Tensor, list[Tensor]], | |
norm_type: float = 2.0, | |
) -> float: | |
""" | |
Returns the norm of the gradients of the given parameters. | |
Args: | |
parameters (Iterable[Tensor] or Tensor): an iterable of Tensors or a | |
single Tensor that will have gradients normalized | |
norm_type (float): type of the used p-norm. | |
Returns: | |
Total norm of the parameter gradients (viewed as a single vector). | |
""" # noqa: E501 | |
if isinstance(parameters, Tensor): | |
parameters = [parameters] | |
grads = [p.grad for p in parameters if p.grad is not None] | |
if len(grads) == 0: | |
return None | |
first_device = grads[0].device | |
grouped_grads: dict[ | |
tuple[torch.device, torch.dtype], list[list[Tensor]] | |
] = _group_tensors_by_device_and_dtype( | |
[[g.detach() for g in grads]] | |
) # type: ignore[assignment] | |
norms = [] | |
for (device, _), ([grads], _) in grouped_grads.items(): | |
if _has_foreach_support(grads, device=device): | |
norms.extend(torch._foreach_norm(grads, norm_type)) | |
else: | |
norms.extend([torch.norm(g, norm_type) for g in grads]) | |
return torch.norm(torch.stack([norm.to(first_device) for norm in norms]), norm_type) | |
class GradNormMonitor(Callback): | |
""" | |
Callback that computes the gradient norm of the model parameters. | |
""" | |
def __init__( | |
self, | |
norm_type: float = 2.0, | |
logging_interval: str = "step", | |
sub_module: Optional[Union[str, list[str]]] = None, | |
) -> None: | |
""" | |
Args: | |
norm_type (float): type of the used p-norm. | |
logging_interval (str): "step" or "epoch". | |
""" | |
super().__init__() | |
self.norm_type = norm_type | |
self.logging_interval = logging_interval | |
self.sub_module = sub_module | |
def on_after_backward(self, trainer: Trainer, model: LightningModule) -> None: | |
""" | |
Computes the gradient norm of the model parameters and logs it to the logger. | |
Args: | |
trainer (Trainer): The trainer object | |
model (LightningModule): The current lightningModule | |
""" | |
lightning_model = model | |
if self.sub_module is None: | |
return self.log_sub_module_grad_norm(lightning_model, model, "") | |
sub_modules = self.sub_module | |
if isinstance(sub_modules, str): | |
sub_modules = [sub_modules] | |
for sub_module in sub_modules: | |
self.log_sub_module_grad_norm( | |
lightning_model, getattr(model, sub_module), f"/{sub_module}" | |
) | |
def log_sub_module_grad_norm( | |
self, lightning_model: LightningModule, model: nn.Module, path: str | |
) -> None: | |
grad_norm_val = grad_norm(model.parameters(), self.norm_type) | |
if grad_norm_val is None: | |
return | |
on_step = self.logging_interval == "step" | |
lightning_model.log( | |
f"train{path}/grad_norm", | |
grad_norm_val, | |
on_step=on_step, | |
on_epoch=not on_step, | |
) | |