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# ------------------------------------------------------------------------------------------
# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
# ------------------------------------------------------------------------------------------
import torch
import torch.nn as nn
import torch.nn.functional as F
import math
from typing import Optional, List
class LoRALayer():
def __init__(
self,
r: int,
lora_alpha: int,
lora_dropout: float,
merge_weights: bool,
):
self.r = r
self.lora_alpha = lora_alpha
# Optional dropout
if lora_dropout > 0.:
self.lora_dropout = nn.Dropout(p=lora_dropout)
else:
self.lora_dropout = lambda x: x
# Mark the weight as unmerged
self.merged = False
self.merge_weights = merge_weights
class Embedding(nn.Embedding, LoRALayer):
# LoRA implemented in a dense layer
def __init__(
self,
num_embeddings: int,
embedding_dim: int,
r: int = 0,
lora_alpha: int = 1,
merge_weights: bool = True,
**kwargs
):
nn.Embedding.__init__(self, num_embeddings, embedding_dim, **kwargs)
LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=0,
merge_weights=merge_weights)
# Actual trainable parameters
if r > 0:
self.lora_A = nn.Parameter(self.weight.new_zeros((r, num_embeddings)))
self.lora_B = nn.Parameter(self.weight.new_zeros((embedding_dim, r)))
self.scaling = self.lora_alpha / self.r
# Freezing the pre-trained weight matrix
self.weight.requires_grad = False
self.reset_parameters()
def reset_parameters(self):
nn.Embedding.reset_parameters(self)
if hasattr(self, 'lora_A'):
# initialize A the same way as the default for nn.Linear and B to zero
nn.init.zeros_(self.lora_A)
nn.init.normal_(self.lora_B)
def train(self, mode: bool = True):
nn.Embedding.train(self, mode)
if mode:
if self.merge_weights and self.merged:
# Make sure that the weights are not merged
if self.r > 0:
self.weight.data -= (self.lora_B @ self.lora_A).transpose(0, 1) * self.scaling
self.merged = False
else:
if self.merge_weights and not self.merged:
# Merge the weights and mark it
if self.r > 0:
self.weight.data += (self.lora_B @ self.lora_A).transpose(0, 1) * self.scaling
self.merged = True
def forward(self, x: torch.Tensor):
if self.r > 0 and not self.merged:
result = nn.Embedding.forward(self, x)
if self.r > 0:
after_A = F.embedding(
x, self.lora_A.transpose(0, 1), self.padding_idx, self.max_norm,
self.norm_type, self.scale_grad_by_freq, self.sparse
)
result += (after_A @ self.lora_B.transpose(0, 1)) * self.scaling
return result
else:
return nn.Embedding.forward(self, x)
class Linear(nn.Linear, LoRALayer):
# LoRA implemented in a dense layer
def __init__(
self,
in_features: int,
out_features: int,
r: int = 0,
lora_alpha: int = 1,
lora_dropout: float = 0.,
fan_in_fan_out: bool = False, # Set this to True if the layer to replace stores weight like (fan_in, fan_out)
merge_weights: bool = True,
**kwargs
):
nn.Linear.__init__(self, in_features, out_features, **kwargs)
LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=lora_dropout,
merge_weights=merge_weights)
self.fan_in_fan_out = fan_in_fan_out
# Actual trainable parameters
if r > 0:
self.lora_A = nn.Parameter(self.weight.new_zeros((r, in_features)))
self.lora_B = nn.Parameter(self.weight.new_zeros((out_features, r)))
self.scaling = self.lora_alpha / self.r
# Freezing the pre-trained weight matrix
self.weight.requires_grad = False
self.reset_parameters()
if fan_in_fan_out:
self.weight.data = self.weight.data.transpose(0, 1)
def reset_parameters(self):
nn.Linear.reset_parameters(self)
if hasattr(self, 'lora_A'):
# initialize A the same way as the default for nn.Linear and B to zero
nn.init.kaiming_uniform_(self.lora_A, a=math.sqrt(5))
nn.init.zeros_(self.lora_B)
def train(self, mode: bool = True):
def T(w):
return w.transpose(0, 1) if self.fan_in_fan_out else w
nn.Linear.train(self, mode)
if mode:
if self.merge_weights and self.merged:
# Make sure that the weights are not merged
if self.r > 0:
self.weight.data -= T(self.lora_B @ self.lora_A) * self.scaling
self.merged = False
else:
if self.merge_weights and not self.merged:
# Merge the weights and mark it
if self.r > 0:
self.weight.data += T(self.lora_B @ self.lora_A) * self.scaling
self.merged = True
def forward(self, x: torch.Tensor):
def T(w):
return w.transpose(0, 1) if self.fan_in_fan_out else w
if self.r > 0 and not self.merged:
result = F.linear(x, T(self.weight), bias=self.bias)
if self.r > 0:
result += (self.lora_dropout(x) @ self.lora_A.transpose(0, 1) @ self.lora_B.transpose(0, 1)) * self.scaling
return result
else:
return F.linear(x, T(self.weight), bias=self.bias)
class MergedLinear(nn.Linear, LoRALayer):
# LoRA implemented in a dense layer
def __init__(
self,
in_features: int,
out_features: int,
r: int = 0,
lora_alpha: int = 1,
lora_dropout: float = 0.,
enable_lora: List[bool] = [False],
fan_in_fan_out: bool = False,
merge_weights: bool = True,
**kwargs
):
nn.Linear.__init__(self, in_features, out_features, **kwargs)
LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=lora_dropout,
merge_weights=merge_weights)
assert out_features % len(enable_lora) == 0, \
'The length of enable_lora must divide out_features'
self.enable_lora = enable_lora
self.fan_in_fan_out = fan_in_fan_out
# Actual trainable parameters
if r > 0 and any(enable_lora):
self.lora_A = nn.Parameter(
self.weight.new_zeros((r * sum(enable_lora), in_features)))
self.lora_B = nn.Parameter(
self.weight.new_zeros((out_features // len(enable_lora) * sum(enable_lora), r))
) # weights for Conv1D with groups=sum(enable_lora)
self.scaling = self.lora_alpha / self.r
# Freezing the pre-trained weight matrix
self.weight.requires_grad = False
# Compute the indices
self.lora_ind = self.weight.new_zeros(
(out_features, ), dtype=torch.bool
).view(len(enable_lora), -1)
self.lora_ind[enable_lora, :] = True
self.lora_ind = self.lora_ind.view(-1)
self.reset_parameters()
if fan_in_fan_out:
self.weight.data = self.weight.data.transpose(0, 1)
def reset_parameters(self):
nn.Linear.reset_parameters(self)
if hasattr(self, 'lora_A'):
# initialize A the same way as the default for nn.Linear and B to zero
nn.init.kaiming_uniform_(self.lora_A, a=math.sqrt(5))
nn.init.zeros_(self.lora_B)
def zero_pad(self, x):
result = x.new_zeros((*x.shape[:-1], self.out_features))
result = result.view(-1, self.out_features)
result[:, self.lora_ind] = x.reshape(
-1, self.out_features // len(self.enable_lora) * sum(self.enable_lora)
)
return result.view((*x.shape[:-1], self.out_features))
def train(self, mode: bool = True):
def T(w):
return w.transpose(0, 1) if self.fan_in_fan_out else w
nn.Linear.train(self, mode)
print(f"lora.train, scaling = {self.scaling}, mode = {mode}, merge_weights = {self.merge_weights}, merged = {self.merged}")
if mode:
if self.merge_weights and self.merged:
# Make sure that the weights are not merged
if self.r > 0 and any(self.enable_lora):
delta_w = F.conv1d(
self.lora_A.data.unsqueeze(0),
self.lora_B.data.unsqueeze(-1),
groups=sum(self.enable_lora)
).squeeze(0)
self.weight.data -= self.zero_pad(T(delta_w * self.scaling))
self.merged = False
else:
if self.merge_weights and not self.merged:
# Merge the weights and mark it
if self.r > 0 and any(self.enable_lora):
delta_w = F.conv1d(
self.lora_A.data.unsqueeze(0),
self.lora_B.data.unsqueeze(-1),
groups=sum(self.enable_lora)
).squeeze(0)
self.weight.data += self.zero_pad(T(delta_w * self.scaling))
self.merged = True
def forward(self, x: torch.Tensor):
def T(w):
return w.transpose(0, 1) if self.fan_in_fan_out else w
if self.merged:
return F.linear(x, T(self.weight), bias=self.bias)
else:
result = F.linear(x, T(self.weight), bias=self.bias)
if self.r > 0:
after_A = F.linear(self.lora_dropout(x), self.lora_A)
after_B = F.conv1d(
after_A.transpose(-2, -1),
self.lora_B.unsqueeze(-1),
groups=sum(self.enable_lora)
).transpose(-2, -1)
result += self.zero_pad(after_B) * self.scaling
return result
class ConvLoRA(nn.Module, LoRALayer):
def __init__(self, conv_module, in_channels, out_channels, kernel_size, r=0, lora_alpha=1, lora_dropout=0., merge_weights=True, **kwargs):
super(ConvLoRA, self).__init__()
self.conv = conv_module(in_channels, out_channels, kernel_size, **kwargs)
LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=lora_dropout, merge_weights=merge_weights)
assert isinstance(kernel_size, int)
# Actual trainable parameters
if r > 0:
self.lora_A = nn.Parameter(
self.conv.weight.new_zeros((r * kernel_size, in_channels * kernel_size))
)
self.lora_B = nn.Parameter(
self.conv.weight.new_zeros((out_channels//self.conv.groups*kernel_size, r*kernel_size))
)
self.scaling = self.lora_alpha / self.r
# Freezing the pre-trained weight matrix
self.conv.weight.requires_grad = False
self.reset_parameters()
self.merged = False
def reset_parameters(self):
self.conv.reset_parameters()
if hasattr(self, 'lora_A'):
# initialize A the same way as the default for nn.Linear and B to zero
nn.init.kaiming_uniform_(self.lora_A, a=math.sqrt(5))
nn.init.zeros_(self.lora_B)
def train(self, mode=True):
super(ConvLoRA, self).train(mode)
if mode:
if self.merge_weights and self.merged:
# Make sure that the weights are not merged
self.conv.weight.data -= (self.lora_B @ self.lora_A).view(self.conv.weight.shape) * self.scaling
self.merged = False
else:
if self.merge_weights and not self.merged:
# Merge the weights and mark it
self.conv.weight.data += (self.lora_B @ self.lora_A).view(self.conv.weight.shape) * self.scaling
self.merged = True
def forward(self, x):
if self.r > 0 and not self.merged:
return self.conv._conv_forward(
x,
self.conv.weight + (self.lora_B @ self.lora_A).view(self.conv.weight.shape) * self.scaling,
self.conv.bias
)
return self.conv(x)
class Conv2d(ConvLoRA):
def __init__(self, *args, **kwargs):
super(Conv2d, self).__init__(nn.Conv2d, *args, **kwargs)
class Conv1d(ConvLoRA):
def __init__(self, *args, **kwargs):
super(Conv1d, self).__init__(nn.Conv1d, *args, **kwargs)
# Can Extend to other ones like this
class Conv3d(ConvLoRA):
def __init__(self, *args, **kwargs):
super(Conv3d, self).__init__(nn.Conv3d, *args, **kwargs)
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