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# Copyright 2023 Salesforce.com, inc.
# Copyright 2023 The HuggingFace Team. All rights reserved.
#
# 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.
from typing import Optional, Tuple, Union
import torch
from torch import nn
from transformers import CLIPPreTrainedModel
from transformers.modeling_outputs import BaseModelOutputWithPooling
from transformers.models.clip.configuration_clip import CLIPTextConfig
from transformers.models.clip.modeling_clip import CLIPEncoder
def _expand_mask(mask: torch.Tensor, dtype: torch.dtype, tgt_len: Optional[int] = None):
"""
Expands attention_mask from `[bsz, seq_len]` to `[bsz, 1, tgt_seq_len, src_seq_len]`.
"""
bsz, src_len = mask.size()
tgt_len = tgt_len if tgt_len is not None else src_len
expanded_mask = mask[:, None, None, :].expand(bsz, 1, tgt_len, src_len).to(dtype)
inverted_mask = 1.0 - expanded_mask
return inverted_mask.masked_fill(inverted_mask.to(torch.bool), torch.finfo(dtype).min)
# This is a modified version of the CLIPTextModel from transformers.models.clip.modeling_clip
# Which allows for an extra input of "context embeddings", which are the query embeddings used in Qformer
# They pass through the clip model, along with the text embeddings, and interact with them using self attention
class ContextCLIPTextModel(CLIPPreTrainedModel):
config_class = CLIPTextConfig
_no_split_modules = ["CLIPEncoderLayer"]
def __init__(self, config: CLIPTextConfig):
super().__init__(config)
self.text_model = ContextCLIPTextTransformer(config)
# Initialize weights and apply final processing
self.post_init()
def forward(
self,
ctx_embeddings: torch.Tensor = None,
ctx_begin_pos: list = None,
input_ids: Optional[torch.Tensor] = None,
attention_mask: Optional[torch.Tensor] = None,
position_ids: Optional[torch.Tensor] = None,
output_attentions: Optional[bool] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
) -> Union[Tuple, BaseModelOutputWithPooling]:
return self.text_model(
ctx_embeddings=ctx_embeddings,
ctx_begin_pos=ctx_begin_pos,
input_ids=input_ids,
attention_mask=attention_mask,
position_ids=position_ids,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
class ContextCLIPTextTransformer(nn.Module):
def __init__(self, config: CLIPTextConfig):
super().__init__()
self.config = config
embed_dim = config.hidden_size
self.embeddings = ContextCLIPTextEmbeddings(config)
self.encoder = CLIPEncoder(config)
self.final_layer_norm = nn.LayerNorm(embed_dim)
def forward(
self,
ctx_embeddings: torch.Tensor,
ctx_begin_pos: list,
input_ids: Optional[torch.Tensor] = None,
attention_mask: Optional[torch.Tensor] = None,
position_ids: Optional[torch.Tensor] = None,
output_attentions: Optional[bool] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
) -> Union[Tuple, BaseModelOutputWithPooling]:
r"""
Returns:
"""
output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
output_hidden_states = (
output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
)
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
if input_ids is None:
raise ValueError("You have to specify either input_ids")
input_shape = input_ids.size()
input_ids = input_ids.view(-1, input_shape[-1])
hidden_states = self.embeddings(
input_ids=input_ids,
position_ids=position_ids,
ctx_embeddings=ctx_embeddings,
ctx_begin_pos=ctx_begin_pos,
)
bsz, seq_len = input_shape
if ctx_embeddings is not None:
seq_len += ctx_embeddings.size(1)
# CLIP's text model uses causal mask, prepare it here.
# https://github.com/openai/CLIP/blob/cfcffb90e69f37bf2ff1e988237a0fbe41f33c04/clip/model.py#L324
causal_attention_mask = self._build_causal_attention_mask(bsz, seq_len, hidden_states.dtype).to(
hidden_states.device
)
# expand attention_mask
if attention_mask is not None:
# [bsz, seq_len] -> [bsz, 1, tgt_seq_len, src_seq_len]
attention_mask = _expand_mask(attention_mask, hidden_states.dtype)
encoder_outputs = self.encoder(
inputs_embeds=hidden_states,
attention_mask=attention_mask,
causal_attention_mask=causal_attention_mask,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
last_hidden_state = encoder_outputs[0]
last_hidden_state = self.final_layer_norm(last_hidden_state)
# text_embeds.shape = [batch_size, sequence_length, transformer.width]
# take features from the eot embedding (eot_token is the highest number in each sequence)
# casting to torch.int for onnx compatibility: argmax doesn't support int64 inputs with opset 14
pooled_output = last_hidden_state[
torch.arange(last_hidden_state.shape[0], device=input_ids.device),
input_ids.to(torch.int).argmax(dim=-1),
]
if not return_dict:
return (last_hidden_state, pooled_output) + encoder_outputs[1:]
return BaseModelOutputWithPooling(
last_hidden_state=last_hidden_state,
pooler_output=pooled_output,
hidden_states=encoder_outputs.hidden_states,
attentions=encoder_outputs.attentions,
)
def _build_causal_attention_mask(self, bsz, seq_len, dtype):
# lazily create causal attention mask, with full attention between the vision tokens
# pytorch uses additive attention mask; fill with -inf
mask = torch.empty(bsz, seq_len, seq_len, dtype=dtype)
mask.fill_(torch.tensor(torch.finfo(dtype).min))
mask.triu_(1) # zero out the lower diagonal
mask = mask.unsqueeze(1) # expand mask
return mask
class ContextCLIPTextEmbeddings(nn.Module):
def __init__(self, config: CLIPTextConfig):
super().__init__()
embed_dim = config.hidden_size
self.token_embedding = nn.Embedding(config.vocab_size, embed_dim)
self.position_embedding = nn.Embedding(config.max_position_embeddings, embed_dim)
# position_ids (1, len position emb) is contiguous in memory and exported when serialized
self.register_buffer("position_ids", torch.arange(config.max_position_embeddings).expand((1, -1)))
def forward(
self,
ctx_embeddings: torch.Tensor,
ctx_begin_pos: list,
input_ids: Optional[torch.LongTensor] = None,
position_ids: Optional[torch.LongTensor] = None,
inputs_embeds: Optional[torch.FloatTensor] = None,
) -> torch.Tensor:
if ctx_embeddings is None:
ctx_len = 0
else:
ctx_len = ctx_embeddings.shape[1]
seq_length = (input_ids.shape[-1] if input_ids is not None else inputs_embeds.shape[-2]) + ctx_len
if position_ids is None:
position_ids = self.position_ids[:, :seq_length]
if inputs_embeds is None:
inputs_embeds = self.token_embedding(input_ids)
# for each input embeddings, add the ctx embeddings at the correct position
input_embeds_ctx = []
bsz = inputs_embeds.shape[0]
if ctx_embeddings is not None:
for i in range(bsz):
cbp = ctx_begin_pos[i]
prefix = inputs_embeds[i, :cbp]
# remove the special token embedding
suffix = inputs_embeds[i, cbp:]
input_embeds_ctx.append(torch.cat([prefix, ctx_embeddings[i], suffix], dim=0))
inputs_embeds = torch.stack(input_embeds_ctx, dim=0)
position_embeddings = self.position_embedding(position_ids)
embeddings = inputs_embeds + position_embeddings
return embeddings
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