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# coding=utf-8
# Copyright 2024 the HuggingFace Inc. team. All rights reserved.
#
# This code is based on EleutherAI's GPT-NeoX library and the GPT-NeoX
# and OPT implementations in this library. It has been modified from its
# original forms to accommodate minor architectural differences compared
# to GPT-NeoX and OPT used by the Meta AI team that trained the model.
#
# 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 torch import nn
from transformers.activations import ACT2FN
import torch.nn.functional as F
class MLP(nn.Module):
def __init__(self, activation, input_size, intermediate_size, output_size):
super().__init__()
self.input_size = input_size
self.intermediate_size = intermediate_size
self.output_size = output_size
self.gate_proj = nn.Linear(input_size, intermediate_size, bias=False)
self.up_proj = nn.Linear(input_size, intermediate_size, bias=False)
self.down_proj = nn.Linear(intermediate_size, output_size, bias=False)
self.act_fn = ACT2FN[activation]
def forward(self, x):
return self.down_proj(self.act_fn(self.gate_proj(x)) * self.up_proj(x))
# Copied from transformers.models.llama.modeling_llama.LlamaRMSNorm
class RMSNorm(nn.Module):
def __init__(self, hidden_size, eps=1e-6):
"""
RMSNorm is equivalent to T5LayerNorm
"""
super().__init__()
self.weight = nn.Parameter(torch.ones(hidden_size))
self.variance_epsilon = eps
def forward(self, hidden_states):
input_dtype = hidden_states.dtype
hidden_states = hidden_states.to(torch.float32)
variance = hidden_states.pow(2).mean(-1, keepdim=True)
hidden_states = hidden_states * torch.rsqrt(variance + self.variance_epsilon)
return self.weight * hidden_states.to(input_dtype)
class DecoupledEmbedding(nn.Embedding):
# Derived from https://pytorch.org/docs/stable/_modules/torch/nn/modules/sparse.html#Embedding
"""
Implements a decoupling of parameters to allow freezing (or not) a subset of the embeddings.
In practise, the regular `weight` can be trained or frozen (i.e. `partially_freeze=True`), and if `num_additional_embeddings` > 0, then it will create `num_additional_embeddings` additional parameters that are always trained.
If `num_additional_embeddings=0`, then the module defaults back to the regular behavior of `nn.Embedding`.
"""
def __init__(
self,
num_embeddings,
num_additional_embeddings,
embedding_dim,
partially_freeze=False,
device=None,
dtype=None,
padding_idx=None,
**kwargs,
) -> None:
"""
num_additional_embeddings: int. Number of additional embeddings. Only useful when you `partially_freeze=True`.
partially_freeze: bool. If True, the regular `weight` will be frozen. `additional_weight` is never frozen.
Note: there are a lot of other parameters to initialize a standard `nn.Embedding` such as `padding_idx`, `max_norm` or `norm_type`. We are not supporting these.
"""
if padding_idx is not None and padding_idx > num_embeddings:
raise ValueError(f"padding_idx must be within num_embeddings. Got {padding_idx} and {num_embeddings}")
super().__init__(
num_embeddings=num_embeddings,
embedding_dim=embedding_dim,
device=device,
dtype=dtype,
padding_idx=padding_idx,
**kwargs,
)
self.num_embeddings = num_embeddings
self.padding_idx = padding_idx
self.num_additional_embeddings = num_additional_embeddings
self.partially_freeze = partially_freeze
if partially_freeze:
self.weight.requires_grad_(False)
if self.num_additional_embeddings > 0:
self.additional_embedding = nn.Embedding(
num_embeddings=self.num_additional_embeddings,
embedding_dim=embedding_dim,
device=device,
dtype=dtype,
)
def forward(self, input_ids):
"""
we have 2 embeddings, with different indices - one pretrained self.weight and another
self.additional_embedding.weight that is being trained.
in order to make a lookup of the input ids, we:
1. find out the indices of the entries belonging to the 2nd embedding
2. extract those values while subtracting the size of the first embedding (num_embeddings),
since the 2nd embedding starts from 0 and not num_embeddings
3. perform the 2nd embedding lookup
4. now we handle the 1st embedding, we overwrite indices belonging to the 2nd embedding with a padding index
5. perform the 1st embedding lookup
6. now we overwrite the values in the 1st embedding lookup with the values of the 2nd embedding lookup
note: for the 1st embedding lookup we could have looked up only the low indices and not do
the padding, but then we have to create a new tensor and populate it with 2 tensors that are
spread out across various indices - i.e. not a simple concat - I haven't benchmarked the
complex case if it's any faster, given that seqlens are usually relatively short it's
probably not faster or if faster not by much - but might be a good idea to measure.
"""
if self.num_additional_embeddings == 0:
return self.additional_embedding(input_ids)
# Clone so that we don't modify the original input_ids later on
input_ids = input_ids.clone()
additional_vocab_indices = torch.where(input_ids >= self.num_embeddings)
input_ids_additional_vocab = input_ids[additional_vocab_indices]
additional_embeddings = self.additional_embedding(input_ids_additional_vocab - self.num_embeddings)
# for successful lookup replace input_ids with 0, the results of these will be discarded anyway
input_ids[additional_vocab_indices] = 0
full_vector = F.embedding(input_ids, self.weight)
# overwrite the records with high indices
full_vector[additional_vocab_indices] = additional_embeddings
return full_vector
def extra_repr(self) -> str:
return "num_embeddings={}, num_additional_embeddings={}, embedding_dim={}, partially_freeze={}".format(
self.num_embeddings,
self.num_additional_embeddings,
self.embedding_dim,
self.partially_freeze,
)
@classmethod
def from_pretrained(cls, embeddings, freeze=True, **kwargs):
raise NotImplementedError
class DecoupledLinear(nn.Linear):
# Derived from https://pytorch.org/docs/stable/_modules/torch/nn/modules/linear.html#Linear
"""
Implements a decoupling of parameters to allow freezing (or not) a subset of the parameters.
In practise, the regular `weight` can be trained or frozen (i.e. `partially_freeze=True`), and if `out_additional_features` > 0, then it will create `out_additional_features * in_features` additional parameters that are always trained.
If `out_additional_features=0`, then the module defaults back to the regular behavior of `nn.Linear`.
"""
def __init__(
self,
in_features: int,
out_features: int,
out_additional_features: int = 0,
bias: bool = True,
partially_freeze: bool = True,
device=None,
dtype=None,
) -> None:
"""
out_additional_features: int. Number of additional trainable dimensions. Only makes sense when `partially_freeze=True`.
partially_freeze: bool. If True, the regular `weight` will be frozen and extra parameters (if any) will be trainable. If False, default to the regular behavior of nn.Linear.
"""
super().__init__(in_features, out_features, bias, device, dtype)
self.out_additional_features = out_additional_features
self.partially_freeze = partially_freeze
self.in_features = in_features
self.out_features = out_features
if partially_freeze:
self.weight.requires_grad_(False)
if bias:
self.bias.requires_grad_(False)
if out_additional_features > 0:
self.additional_fc = nn.Linear(
in_features=in_features,
out_features=out_additional_features,
bias=bias,
device=device,
dtype=dtype,
)
def forward(self, input: torch.Tensor) -> torch.Tensor:
output = F.linear(input, self.weight, self.bias)
if self.out_additional_features > 0:
additional_features = self.additional_fc(input)
output = torch.cat((output, additional_features), -1)
return output
def extra_repr(self) -> str:
"""Overwriting `nn.Linear.extra_repr` to include new parameters."""
return "in_features={}, out_features={}, out_additional_features={}, bias={}, partially_freeze={}".format(
self.in_features,
self.out_features,
self.out_additional_features,
self.bias is not None,
self.partially_freeze,
)
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