# Copyright 2022 Cerebras Systems.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import torch
from modelzoo.common.pytorch.optim.CSOptimizer import CSOptimizer
[docs]class RMSprop(CSOptimizer):
"""
RMSprop optimizer implemented to perform the required
pre-initialization of the optimizer state.
"""
[docs] def __init__(
self,
params,
lr=1e-2,
alpha=0.99,
eps=1e-8,
weight_decay=0,
momentum=0,
centered=False,
):
if not 0.0 <= lr:
raise ValueError("Invalid learning rate: {}".format(lr))
if not 0.0 <= eps:
raise ValueError("Invalid epsilon value: {}".format(eps))
if not 0.0 <= momentum:
raise ValueError("Invalid momentum value: {}".format(momentum))
if not 0.0 <= weight_decay:
raise ValueError(
"Invalid weight_decay value: {}".format(weight_decay)
)
if not 0.0 <= alpha:
raise ValueError("Invalid alpha value: {}".format(alpha))
defaults = dict(
lr=lr,
momentum=momentum,
alpha=alpha,
eps=eps,
centered=centered,
weight_decay=weight_decay,
)
super(RMSprop, self).__init__(params, defaults)
[docs] def state_names_to_sparsify(self):
return ["square_avg", "momentum_buffer", "grad_avg"]
[docs] def preinitialize(self):
"""
Allocates tensors for the optimizer state to allow direct compilation
of the model before the first step.
"""
for group in self.param_groups:
for p in group['params']:
self.state[p]["square_avg"] = torch.zeros_like(
p, device="cpu"
).to(p.device)
if group['momentum'] > 0:
self.state[p]["momentum_buffer"] = torch.zeros_like(
p, device="cpu"
).to(p.device)
if group['centered']:
self.state[p]["grad_avg"] = torch.zeros_like(
p, device="cpu"
).to(p.device)
@torch.no_grad()
def step(self, closure=None):
"""Performs a single optimization step.
Args:
closure (callable, optional): A closure that reevaluates the model
and returns the loss.
"""
loss = None
if closure is not None:
loss = closure()
for group in self.param_groups:
lr = group["lr"]
alpha = group["alpha"]
weight_decay = group["weight_decay"]
momentum = group["momentum"]
eps = group["eps"]
centered = group["centered"]
for p in group["params"]:
if p.grad is None:
continue
grad = p.grad
if grad.is_sparse:
raise RuntimeError(
"RMSprop does not support sparse gradients."
)
state = self.state[p]
square_avg = state["square_avg"]
if weight_decay != 0:
grad = grad.add(p, alpha=weight_decay)
square_avg.mul_(alpha).addcmul_(grad, grad, value=1.0 - alpha)
if centered:
grad_avg = state["grad_avg"]
grad_avg.mul_(alpha).add_(grad, alpha=1 - alpha)
avg = (
square_avg.addcmul(grad_avg, grad_avg, value=-1.0)
.sqrt_()
.add_(eps)
)
else:
avg = square_avg.sqrt().add_(eps)
if momentum > 0.0:
momentum_buffer = state["momentum_buffer"]
momentum_buffer.mul_(momentum).addcdiv_(grad, avg)
p.add_(-lr * momentum_buffer)
else:
p.addcdiv_(-lr * grad, avg)
return loss