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from typing import List, Dict, Optional, Tuple
import torch
import torch.optim._functional as F
from torch import Tensor
__all__ : List[str] = []
# Define a TorchScript compatible Functional Rprop Optimizer
# where we use these optimizer in a functional way.
# Instead of using the `param.grad` when updating parameters,
# we explicitly allow the distributed optimizer pass gradients to
# the `step` function. In this way, we could separate the gradients
# and parameters and allow multithreaded trainer to update the
# parameters without data traces on accumulating to the same .grad.
# NOTE: This should be only used by distributed optimizer internals
# and not meant to expose to the user.
@torch.jit.script
class _FunctionalRprop(object):
def __init__(
self,
params: List[Tensor],
lr: float = 1e-2,
etas: Tuple[float, float] = (0.5, 1.2),
step_sizes: Tuple[float, float] = (1e-6, 50),
foreach: bool = False,
maximize: bool = False,
_allow_empty_param_list: bool = False,
):
self.defaults = {
"lr": lr,
}
self.etas = etas
self.step_sizes = step_sizes
self.foreach = foreach
self.maximize = maximize
if len(params) == 0 and not _allow_empty_param_list:
raise ValueError("optimizer got an empty parameter list")
# NOTE: we only have one param_group and don't allow user to add additional
# param group as it's not a common use case.
self.param_group = {"params": params}
self.state = torch.jit.annotate(Dict[torch.Tensor, Dict[str, torch.Tensor]], {})
def step(self, gradients: List[Optional[Tensor]]):
params = self.param_group['params']
params_with_grad = []
grads = []
prevs = []
step_sizes = []
lr = self.defaults['lr']
etaminus, etaplus = self.etas
step_size_min, step_size_max = self.step_sizes
if len(params) != len(gradients):
raise ValueError(
"the gradients passed in does not equal to the size of the parameters!"
+ f"Params length: {len(params)}. "
+ f"Gradients length: {len(gradients)}"
)
for param, gradient in zip(params, gradients):
if gradient is not None:
params_with_grad.append(param)
grads.append(gradient)
# Lazy state initialization
if param not in self.state:
self.state[param] = {}
state = self.state[param]
state['step'] = torch.tensor(0.0)
state['prev'] = torch.zeros_like(param, memory_format=torch.preserve_format)
state['step_size'] = torch.full_like(gradient, lr)
state = self.state[param]
prevs.append(state['prev'])
step_sizes.append(state['step_size'])
state['step'] += 1
with torch.no_grad():
F.rprop(params_with_grad,
grads,
prevs,
step_sizes,
step_size_min=step_size_min,
step_size_max=step_size_max,
etaminus=etaminus,
etaplus=etaplus,
foreach=self.foreach,
maximize=self.maximize)
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