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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import torch
from torch.optim import Optimizer
from bitsandbytes.optim.optimizer import Optimizer1State
class LARS(Optimizer1State):
def __init__(self, params, lr, momentum=0, dampening=0,
weight_decay=0, nesterov=False, optim_bits=32, args=None,
min_8bit_size=4096, percentile_clipping=100, max_unorm=0.02):
if momentum == 0:
raise NotImplementedError(f'LARS without momentum is not supported!')
super(LARS, self).__init__('lars', params, lr, (momentum, dampening), 0.0,
weight_decay, optim_bits, args, min_8bit_size, percentile_clipping, max_unorm=max_unorm, block_wise=False)
class LARS8bit(Optimizer1State):
def __init__(self, params, lr, momentum=0, dampening=0,
weight_decay=0, nesterov=False, args=None,
min_8bit_size=4096, percentile_clipping=100, max_unorm=0.02):
if momentum == 0:
raise NotImplementedError(f'LARS without momentum is not supported!')
super(LARS8bit, self).__init__('lars', params, lr, (momentum, dampening), 0.0,
weight_decay, 8, args, min_8bit_size, percentile_clipping, max_unorm=max_unorm, block_wise=False)
class LARS32bit(Optimizer1State):
def __init__(self, params, lr, momentum=0, dampening=0,
weight_decay=0, nesterov=False, args=None,
min_8bit_size=4096, percentile_clipping=100, max_unorm=0.02):
if momentum == 0:
raise NotImplementedError(f'LARS without momentum is not supported!')
super(LARS32bit, self).__init__('lars', params, lr, (momentum, dampening), 0.0,
weight_decay, 32, args, min_8bit_size, percentile_clipping, max_unorm=max_unorm, block_wise=False)
class PytorchLARS(Optimizer):
def __init__(self, params, lr=0.01, momentum=0, dampening=0,
weight_decay=0, nesterov=False, max_unorm=0.02):
if lr < 0.0:
raise ValueError("Invalid learning rate: {}".format(lr))
if momentum < 0.0:
raise ValueError("Invalid momentum value: {}".format(momentum))
if weight_decay < 0.0:
raise ValueError("Invalid weight_decay value: {}".format(weight_decay))
defaults = dict(lr=lr, momentum=momentum, dampening=dampening,
weight_decay=weight_decay, nesterov=nesterov, max_unorm=max_unorm)
if nesterov and (momentum <= 0 or dampening != 0):
raise ValueError("Nesterov momentum requires a momentum and zero dampening")
super(PytorchLARS, self).__init__(params, defaults)
def __setstate__(self, state):
super(PytorchLARS, self).__setstate__(state)
for group in self.param_groups:
group.setdefault('nesterov', False)
@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:
with torch.enable_grad():
loss = closure()
for group in self.param_groups:
params_with_grad = []
d_p_list = []
momentum_buffer_list = []
weight_decay = group['weight_decay']
momentum = group['momentum']
dampening = group['dampening']
nesterov = group['nesterov']
max_unorm = group['max_unorm']
lr = group['lr']
for p in group['params']:
if p.grad is None: continue
state = self.state[p]
d_p = p.grad
if weight_decay != 0:
d_p = d_p.add(param, alpha=weight_decay)
if momentum != 0:
buf = state.get('momentum_buffer', None)
if buf is None:
buf = torch.clone(d_p).detach()
state['momentum_buffer']= buf
else:
buf.mul_(momentum).add_(d_p, alpha=1 - dampening)
if nesterov:
update = d_p + buf*momentum
else:
update = buf
update_scale = 1.0
if max_unorm > 0.0:
assert p.dtype == torch.float32
pnorm = torch.norm(p.detach())
unorm = torch.norm(update)
if unorm > max_unorm*pnorm:
update_scale = max_unorm*pnorm/unorm
p.add_(update, alpha=-lr*update_scale)
return loss
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