Created NORA. She has been designed from zero. At this point, I have determined the best hyperparamers for her to train. Next step is to help her communicate on discord and see how she handles it.
This commit is contained in:
100
model.py
Normal file
100
model.py
Normal file
@ -0,0 +1,100 @@
|
||||
"""
|
||||
model.py
|
||||
|
||||
Defines a Transformer‐based language model from scratch, using PyTorch’s nn.Transformer.
|
||||
No pretrained weights—everything is initialized randomly.
|
||||
"""
|
||||
|
||||
import torch
|
||||
import torch.nn as nn
|
||||
import math
|
||||
|
||||
|
||||
class PositionalEncoding(nn.Module):
|
||||
def __init__(self, d_model: int, max_len: int = 10_000):
|
||||
super().__init__()
|
||||
pe = torch.zeros(max_len, d_model)
|
||||
position = torch.arange(0, max_len, dtype=torch.float).unsqueeze(1)
|
||||
div_term = torch.exp(
|
||||
torch.arange(0, d_model, 2).float() * (-math.log(10000.0) / d_model)
|
||||
)
|
||||
pe[:, 0::2] = torch.sin(position * div_term)
|
||||
pe[:, 1::2] = torch.cos(position * div_term)
|
||||
pe = pe.unsqueeze(0) # shape: (1, max_len, d_model)
|
||||
self.register_buffer("pe", pe)
|
||||
|
||||
def forward(self, x: torch.Tensor) -> torch.Tensor:
|
||||
"""
|
||||
x: (batch_size, seq_length, d_model)
|
||||
returns x + positional encodings for the first seq_length positions.
|
||||
"""
|
||||
x = x + self.pe[:, : x.size(1), :]
|
||||
return x
|
||||
|
||||
|
||||
class NoraTransformerLM(nn.Module):
|
||||
def __init__(
|
||||
self,
|
||||
vocab_size: int,
|
||||
d_model: int = 512,
|
||||
nhead: int = 8,
|
||||
num_layers: int = 6,
|
||||
dim_feedforward: int = 2048,
|
||||
dropout: float = 0.1,
|
||||
max_seq_len: int = 512,
|
||||
):
|
||||
super().__init__()
|
||||
self.model_type = "TransformerLM"
|
||||
self.d_model = d_model
|
||||
self.vocab_size = vocab_size
|
||||
|
||||
# Token embedding + positional encoding
|
||||
self.token_embed = nn.Embedding(vocab_size, d_model)
|
||||
self.pos_encoder = PositionalEncoding(d_model, max_len=max_seq_len)
|
||||
|
||||
# Transformer encoder layers
|
||||
encoder_layers = nn.TransformerEncoderLayer(
|
||||
d_model=d_model,
|
||||
nhead=nhead,
|
||||
dim_feedforward=dim_feedforward,
|
||||
dropout=dropout,
|
||||
activation="gelu",
|
||||
)
|
||||
self.transformer_encoder = nn.TransformerEncoder(
|
||||
encoder_layers, num_layers=num_layers
|
||||
)
|
||||
|
||||
# Final linear layer to project to vocabulary
|
||||
self.fc_out = nn.Linear(d_model, vocab_size)
|
||||
|
||||
# Initialization
|
||||
self._init_weights()
|
||||
|
||||
def _init_weights(self):
|
||||
nn.init.normal_(self.token_embed.weight, mean=0, std=self.d_model ** -0.5)
|
||||
nn.init.zeros_(self.fc_out.bias)
|
||||
nn.init.normal_(self.fc_out.weight, mean=0, std=self.d_model ** -0.5)
|
||||
|
||||
def forward(self, src: torch.Tensor) -> torch.Tensor:
|
||||
"""
|
||||
src: (batch_size, seq_length), token IDs
|
||||
returns: logits (batch_size, seq_length, vocab_size)
|
||||
"""
|
||||
|
||||
# Embed tokens and add positional encoding
|
||||
x = self.token_embed(src) * math.sqrt(self.d_model) # (B, S, D)
|
||||
x = self.pos_encoder(x) # (B, S, D)
|
||||
# PyTorch Transformer expects (S, B, D)
|
||||
x = x.permute(1, 0, 2) # (seq_length, batch_size, d_model)
|
||||
|
||||
# Create a causal mask so each position can only attend to previous positions
|
||||
seq_len = x.size(0)
|
||||
mask = torch.triu(torch.ones(seq_len, seq_len, device=x.device), diagonal=1).bool()
|
||||
|
||||
# Pass through Transformer encoder
|
||||
x = self.transformer_encoder(x, mask=mask) # (seq_length, batch_size, d_model)
|
||||
|
||||
# Back to (B, S, D)
|
||||
x = x.permute(1, 0, 2) # (batch_size, seq_length, d_model)
|
||||
logits = self.fc_out(x) # (batch_size, seq_length, vocab_size)
|
||||
return logits
|
Reference in New Issue
Block a user