You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
142 lines
5.3 KiB
142 lines
5.3 KiB
from typing import List |
|
import torch |
|
from torch import nn, BoolTensor, FloatTensor, LongTensor |
|
|
|
|
|
class GLU(nn.Module): |
|
def __init__(self, count_in_out: int, count_middle: int): |
|
super().__init__() |
|
self.gelu = nn.GELU() |
|
self.ln0 = nn.LayerNorm(count_in_out) |
|
self.ln1 = nn.LayerNorm(count_middle) |
|
self.fc0 = nn.Linear(count_in_out, count_middle, bias=False) |
|
self.fc1 = nn.Linear(count_in_out, count_middle, bias=False) |
|
self.fc2 = nn.Linear(count_middle, count_in_out, bias=False) |
|
|
|
def forward(self, z: FloatTensor) -> FloatTensor: |
|
z = self.ln0.forward(z) |
|
w = self.fc0.forward(z) |
|
w = self.gelu.forward(w) |
|
v = self.fc1.forward(z) |
|
z = self.ln1.forward(w * v) |
|
z = self.fc2.forward(z) |
|
return z |
|
|
|
|
|
class AttentionBase(nn.Module): |
|
def __init__(self, head_count: int, embed_count: int): |
|
super().__init__() |
|
self.head_count = head_count |
|
self.embed_count = embed_count |
|
|
|
self.k_proj = nn.Linear(embed_count, embed_count, bias=False) |
|
self.v_proj = nn.Linear(embed_count, embed_count, bias=False) |
|
self.q_proj = nn.Linear(embed_count, embed_count, bias=False) |
|
self.out_proj = nn.Linear(embed_count, embed_count, bias=False) |
|
|
|
def forward( |
|
self, |
|
keys: FloatTensor, |
|
values: FloatTensor, |
|
queries: FloatTensor, |
|
attention_mask: BoolTensor |
|
) -> FloatTensor: |
|
keys = keys.reshape(keys.shape[:2] + (self.head_count, -1)) |
|
values = values.reshape(values.shape[:2] + (self.head_count, -1)) |
|
queries = queries.reshape(queries.shape[:2] + (self.head_count, -1)) |
|
queries /= queries.shape[-1] ** 0.5 |
|
|
|
attention_bias = (1 - attention_mask.to(torch.float32)) * -1e12 |
|
attention_weights: FloatTensor = torch.einsum( |
|
'bqhc,bkhc->bhqk', |
|
queries, |
|
keys |
|
) |
|
attention_weights += attention_bias[:, None, None, :] |
|
attention_weights = torch.softmax(attention_weights, -1) |
|
attention_output: FloatTensor = torch.einsum( |
|
"bhqk,bkhc->bqhc", |
|
attention_weights, |
|
values |
|
) |
|
shape = attention_output.shape[:2] + (self.embed_count,) |
|
attention_output = attention_output.reshape(shape) |
|
attention_output = self.out_proj.forward(attention_output) |
|
return attention_output |
|
|
|
|
|
class EncoderSelfAttention(AttentionBase): |
|
def forward( |
|
self, |
|
encoder_state: FloatTensor, |
|
attention_mask: BoolTensor |
|
) -> FloatTensor: |
|
keys = self.k_proj.forward(encoder_state) |
|
values = self.v_proj.forward(encoder_state) |
|
queries = self.q_proj.forward(encoder_state) |
|
return super().forward(keys, values, queries, attention_mask) |
|
|
|
|
|
class EncoderLayer(nn.Module): |
|
def __init__(self, embed_count: int, head_count: int, glu_embed_count: int): |
|
super().__init__() |
|
self.pre_self_attn_layer_norm = nn.LayerNorm(embed_count) |
|
self.self_attn = EncoderSelfAttention(head_count, embed_count) |
|
self.self_attn_layer_norm = nn.LayerNorm(embed_count) |
|
self.glu = GLU(embed_count, glu_embed_count) |
|
|
|
def forward( |
|
self, |
|
encoder_state: FloatTensor, |
|
attention_mask: BoolTensor |
|
) -> FloatTensor: |
|
residual = encoder_state |
|
encoder_state = self.pre_self_attn_layer_norm.forward(encoder_state) |
|
encoder_state = self.self_attn.forward(encoder_state, attention_mask) |
|
encoder_state = self.self_attn_layer_norm.forward(encoder_state) |
|
encoder_state = residual + encoder_state |
|
residual = encoder_state |
|
encoder_state = self.glu.forward(encoder_state) |
|
encoder_state = residual + encoder_state |
|
return encoder_state |
|
|
|
|
|
class DalleBartEncoder(nn.Module): |
|
def __init__( |
|
self, |
|
layer_count: int, |
|
embed_count: int, |
|
attention_head_count: int, |
|
text_vocab_count: int, |
|
text_token_count: int, |
|
glu_embed_count: int, |
|
device: str |
|
): |
|
super().__init__() |
|
self.text_vocab_count = text_vocab_count |
|
self.embed_tokens = nn.Embedding(text_vocab_count, embed_count) |
|
self.embed_positions = nn.Embedding(text_token_count, embed_count) |
|
self.layers: List[EncoderLayer] = nn.ModuleList([ |
|
EncoderLayer( |
|
embed_count = embed_count, |
|
head_count = attention_head_count, |
|
glu_embed_count = glu_embed_count |
|
) |
|
for _ in range(layer_count) |
|
]) |
|
self.layernorm_embedding = nn.LayerNorm(embed_count) |
|
self.final_ln = nn.LayerNorm(embed_count) |
|
token_indices = torch.arange(text_token_count, device=device) |
|
self.pose_tokens = torch.stack([token_indices] * 2) |
|
|
|
def forward(self, text_tokens: LongTensor) -> FloatTensor: |
|
attention_mask = text_tokens.not_equal(1) |
|
encoder_state = ( |
|
self.embed_tokens.forward(text_tokens) + |
|
self.embed_positions.forward(self.pose_tokens) |
|
) |
|
encoder_state = self.layernorm_embedding.forward(encoder_state) |
|
for layer in self.layers: |
|
encoder_state = layer.forward(encoder_state, attention_mask) |
|
encoder_state = self.final_ln.forward(encoder_state) |
|
return encoder_state |