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# Copyright (c) 2022, Tri Dao.
""""
The implementation was adopted from
https://github.com/Dao-AILab/flash-attention/blob/43950dda456e095969d842fca7a73c5bfe3cecd0/flash_attn/models/bert.py
"""
import torch
import torch.nn as nn
from torch import Tensor
class BertEmbeddings(nn.Module):
def __init__(
self,
embed_dim,
vocab_size,
max_position_embeddings,
type_vocab_size,
padding_idx=None,
device=None,
dtype=None,
):
"""
If max_position_embeddings <= 0, there's no position embeddings
If type_vocab_size <= 0, there's no token type embeddings
"""
factory_kwargs = {"device": device, "dtype": dtype}
super().__init__()
self.word_embeddings = nn.Embedding(
vocab_size, embed_dim, padding_idx=padding_idx, **factory_kwargs
)
self.max_position_embeddings = max_position_embeddings
self.type_vocab_size = type_vocab_size
if self.max_position_embeddings > 0:
self.position_embeddings = nn.Embedding(
max_position_embeddings, embed_dim, **factory_kwargs
)
if self.type_vocab_size > 0:
self.token_type_embeddings = nn.Embedding(type_vocab_size, embed_dim, **factory_kwargs)
def forward(self, input_ids, position_ids=None, token_type_ids=None):
"""
input_ids: (batch, seqlen)
position_ids: (batch, seqlen)
token_type_ids: (batch, seqlen)
"""
batch_size, seqlen = input_ids.shape
embeddings = self.word_embeddings(input_ids)
if self.max_position_embeddings > 0:
if position_ids is None:
position_ids = torch.arange(seqlen, dtype=torch.long, device=input_ids.device)
position_embeddings = self.position_embeddings(position_ids)
embeddings = embeddings + position_embeddings
if self.type_vocab_size > 0:
if token_type_ids is None:
token_type_ids = torch.zeros(seqlen, dtype=torch.long, device=input_ids.device)
token_type_embeddings = self.token_type_embeddings(token_type_ids)
embeddings = embeddings + token_type_embeddings
return embeddings
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