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Zero
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# Copyright 2023-present the HuggingFace Inc. team.
#
# 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.
# Based on https://github.com/THUDM/P-tuning-v2/blob/main/model/prefix_encoder.py
# with some refactor
import torch
class PrefixEncoder(torch.nn.Module):
r"""
The `torch.nn` model to encode the prefix.
Args:
config ([`PrefixTuningConfig`]): The configuration of the prefix encoder.
Example:
```py
>>> from peft import PrefixEncoder, PrefixTuningConfig
>>> config = PrefixTuningConfig(
... peft_type="PREFIX_TUNING",
... task_type="SEQ_2_SEQ_LM",
... num_virtual_tokens=20,
... token_dim=768,
... num_transformer_submodules=1,
... num_attention_heads=12,
... num_layers=12,
... encoder_hidden_size=768,
... )
>>> prefix_encoder = PrefixEncoder(config)
```
**Attributes**:
- **embedding** (`torch.nn.Embedding`) -- The embedding layer of the prefix encoder.
- **transform** (`torch.nn.Sequential`) -- The two-layer MLP to transform the prefix embeddings if
`prefix_projection` is `True`.
- **prefix_projection** (`bool`) -- Whether to project the prefix embeddings.
Input shape: (`batch_size`, `num_virtual_tokens`)
Output shape: (`batch_size`, `num_virtual_tokens`, `2*layers*hidden`)
"""
def __init__(self, config):
super().__init__()
self.prefix_projection = config.prefix_projection
token_dim = config.token_dim
num_layers = config.num_layers
encoder_hidden_size = config.encoder_hidden_size
num_virtual_tokens = config.num_virtual_tokens
if self.prefix_projection and not config.inference_mode:
# Use a two-layer MLP to encode the prefix
self.embedding = torch.nn.Embedding(num_virtual_tokens, token_dim)
self.transform = torch.nn.Sequential(
torch.nn.Linear(token_dim, encoder_hidden_size),
torch.nn.Tanh(),
torch.nn.Linear(encoder_hidden_size, num_layers * 2 * token_dim),
)
else:
self.embedding = torch.nn.Embedding(num_virtual_tokens, num_layers * 2 * token_dim)
def forward(self, prefix: torch.Tensor):
if self.prefix_projection:
prefix_tokens = self.embedding(prefix)
past_key_values = self.transform(prefix_tokens)
else:
past_key_values = self.embedding(prefix)
return past_key_values
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