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from transformers import PreTrainedModel
import torch
import torch.nn as nn
from torch.nn import functional as F
from .config import BharatAIConfig
batch_size = 4
block_size = 128
max_iters = 10
learning_rate = 3e-4
eval_iters = 100
device = 'cuda' if torch.cuda.is_available() else 'cpu'
print(device)
# n_embd = 384
# n_head = 4
# n_layer = 4
dropout = 0.2
# vocab_size=1000
# model architecture
class Head(nn.Module):
""" one head of self-attention """
def __init__(self, n_embd, head_size):
super().__init__()
self.key = nn.Linear(n_embd, head_size, bias=False)
self.query = nn.Linear(n_embd, head_size, bias=False)
self.value = nn.Linear(n_embd, head_size, bias=False)
self.register_buffer('tril', torch.tril(torch.ones(block_size, block_size)))
self.dropout = nn.Dropout(dropout)
def forward(self, x):
# input of size (batch, time-step, channels)
# output of size (batch, time-step, head size)
B,T,C = x.shape
k = self.key(x) # (B,T,hs)
q = self.query(x) # (B,T,hs)
# compute attention scores ("affinities")
wei = q @ k.transpose(-2,-1) * k.shape[-1]**-0.5 # (B, T, hs) @ (B, hs, T) -> (B, T, T)
wei = wei.masked_fill(self.tril[:T, :T] == 0, float('-inf')) # (B, T, T)
wei = F.softmax(wei, dim=-1) # (B, T, T)
wei = self.dropout(wei)
# perform the weighted aggregation of the values
v = self.value(x) # (B,T,hs)
out = wei @ v # (B, T, T) @ (B, T, hs) -> (B, T, hs)
return out
class MultiHeadAttention(nn.Module):
""" multiple heads of self-attention in parallel """
def __init__(self, num_heads, head_size, n_embd):
super().__init__()
self.heads = nn.ModuleList([Head(n_embd,head_size) for _ in range(num_heads)])
self.proj = nn.Linear(head_size * num_heads, n_embd)
self.dropout = nn.Dropout(dropout)
def forward(self, x):
out = torch.cat([h(x) for h in self.heads], dim=-1) # (B, T, F) -> (B, T, [h1, h1, h1, h1, h2, h2, h2, h2, h3, h3, h3, h3])
out = self.dropout(self.proj(out))
return out
class FeedFoward(nn.Module):
""" a simple linear layer followed by a non-linearity """
def __init__(self, n_embd):
super().__init__()
self.net = nn.Sequential(
nn.Linear(n_embd, 4 * n_embd),
nn.ReLU(),
nn.Linear(4 * n_embd, n_embd),
nn.Dropout(dropout),
)
def forward(self, x):
return self.net(x)
class Block(nn.Module):
""" Transformer block: communication followed by computation """
def __init__(self, n_embd, n_head):
# n_embd: embedding dimension, n_head: the number of heads we'd like
super().__init__()
head_size = n_embd // n_head
self.sa = MultiHeadAttention(n_head, head_size,n_embd)
self.ffwd = FeedFoward(n_embd)
self.ln1 = nn.LayerNorm(n_embd)
self.ln2 = nn.LayerNorm(n_embd)
def forward(self, x):
y = self.sa(x)
x = self.ln1(x + y)
y = self.ffwd(x)
x = self.ln2(x + y)
return x
class BharatAI(PreTrainedModel):
config_class = BharatAIConfig
def __init__(self, config):
super().__init__(config)
self.token_embedding_table = nn.Embedding(config.vocab_size, config.n_embd)
self.position_embedding_table = nn.Embedding(block_size, config.n_embd)
self.blocks = nn.Sequential(*[Block(config.n_embd, n_head=config.n_head) for _ in range(config.n_layer)])
self.ln_f = nn.LayerNorm(config.n_embd) # final layer norm
self.lm_head = nn.Linear(config.n_embd, config.vocab_size)
self.apply(self._init_weights)
def _init_weights(self, module):
if isinstance(module, nn.Linear):
torch.nn.init.normal_(module.weight, mean=0.0, std=0.02)
if module.bias is not None:
torch.nn.init.zeros_(module.bias)
elif isinstance(module, nn.Embedding):
torch.nn.init.normal_(module.weight, mean=0.0, std=0.02)
def forward(self, index, targets=None):
B, T = index.shape
# idx and targets are both (B,T) tensor of integers
tok_emb = self.token_embedding_table(index) # (B,T,C)
pos_emb = self.position_embedding_table(torch.arange(T, device=device)) # (T,C)
x = tok_emb + pos_emb # (B,T,C)
x = self.blocks(x) # (B,T,C)
x = self.ln_f(x) # (B,T,C)
logits = self.lm_head(x) # (B,T,vocab_size)
if targets is None:
loss = None
else:
B, T, C = logits.shape
logits = logits.view(B*T, C)
targets = targets.view(B*T)
loss = F.cross_entropy(logits, targets)
return logits, loss
def generate(self, index, max_new_tokens):
# index is (B, T) array of indices in the current context
for _ in range(max_new_tokens):
# crop idx to the last block_size tokens
index_cond = index[:, -block_size:]
# get the predictions
logits, loss = self.forward(index_cond)
# focus only on the last time step
logits = logits[:, -1, :] # becomes (B, C)
# apply softmax to get probabilities
probs = F.softmax(logits, dim=-1) # (B, C)
# sample from the distribution
index_next = torch.multinomial(probs, num_samples=1) # (B, 1)
# append sampled index to the running sequence
index = torch.cat((index, index_next), dim=1) # (B, T+1)
return index
# config = BharatAIConfig(
# vocab_size=1000,
# n_embd=384,
# n_head=4,
# n_layer=4,
# dropout=0.2,
# # any other parameters you want to set
# )
# model = CustomAI(config)
# # model.load_state_dict(torch.load('/content/BharatAI.pth'))
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