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			610 lines
		
	
	
		
			21 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
			
		
		
	
	
			610 lines
		
	
	
		
			21 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
| # Copyright (c) Sebastian Raschka under Apache License 2.0 (see LICENSE.txt).
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| # Source for "Build a Large Language Model From Scratch"
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| #   - https://www.manning.com/books/build-a-large-language-model-from-scratch
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| # Code: https://github.com/rasbt/LLMs-from-scratch
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| 
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| 
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| import os
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| import time
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| import urllib.request
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| 
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| import matplotlib.pyplot as plt
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| import torch
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| import torch.nn as nn
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| from torch.utils.data import Dataset, DataLoader
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| import tiktoken
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| 
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| # NEW imports (see Appendix A):
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| import platform
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| from torch.utils.data.distributed import DistributedSampler
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| from torch.nn.parallel import DistributedDataParallel as DDP
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| from torch.distributed import init_process_group, destroy_process_group
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| 
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| 
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| # NEW: function to initialize a distributed process group (1 process / GPU)
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| # this allows communication among processes
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| # (see Appendix A):
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| def ddp_setup(rank, world_size):
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|     """
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|     Arguments:
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|         rank: a unique process ID
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|         world_size: total number of processes in the group
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|     """
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|     # Only set MASTER_ADDR and MASTER_PORT if not already defined by torchrun
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|     if "MASTER_ADDR" not in os.environ:
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|         os.environ["MASTER_ADDR"] = "localhost"
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|     if "MASTER_PORT" not in os.environ:
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|         os.environ["MASTER_PORT"] = "12345"
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| 
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|     # initialize process group
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|     if platform.system() == "Windows":
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|         # Disable libuv because PyTorch for Windows isn't built with support
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|         os.environ["USE_LIBUV"] = "0"
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|         # Windows users may have to use "gloo" instead of "nccl" as backend
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|         # gloo: Facebook Collective Communication Library
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|         init_process_group(backend="gloo", rank=rank, world_size=world_size)
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|     else:
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|         # nccl: NVIDIA Collective Communication Library
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|         init_process_group(backend="nccl", rank=rank, world_size=world_size)
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| 
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|     torch.cuda.set_device(rank)
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| 
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| 
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| #####################################
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| # Chapter 2
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| #####################################
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| 
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| 
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| class GPTDatasetV1(Dataset):
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|     def __init__(self, txt, tokenizer, max_length, stride):
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|         self.input_ids = []
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|         self.target_ids = []
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| 
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|         # Tokenize the entire text
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|         token_ids = tokenizer.encode(txt, allowed_special={"<|endoftext|>"})
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| 
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|         # Use a sliding window to chunk the book into overlapping sequences of max_length
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|         for i in range(0, len(token_ids) - max_length, stride):
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|             input_chunk = token_ids[i:i + max_length]
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|             target_chunk = token_ids[i + 1: i + max_length + 1]
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|             self.input_ids.append(torch.tensor(input_chunk))
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|             self.target_ids.append(torch.tensor(target_chunk))
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| 
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|     def __len__(self):
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|         return len(self.input_ids)
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| 
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|     def __getitem__(self, idx):
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|         return self.input_ids[idx], self.target_ids[idx]
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| 
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| 
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| # NEW: Modify to set shuffle=False and use a sampler
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| # (See Appendix A):
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| def create_dataloader_v1(txt, batch_size=4, max_length=256,
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|                          stride=128, drop_last=True, num_workers=0):
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|     # Initialize the tokenizer
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|     tokenizer = tiktoken.get_encoding("gpt2")
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| 
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|     # Create dataset
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|     dataset = GPTDatasetV1(txt, tokenizer, max_length, stride)
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| 
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|     # Create dataloader
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|     dataloader = DataLoader(
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|         dataset=dataset,
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|         batch_size=batch_size,
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|         shuffle=False,  # NEW: False because of DistributedSampler below
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|         drop_last=drop_last,
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|         num_workers=num_workers,
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|         pin_memory=True,
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|         # NEW: chunk batches across GPUs without overlapping samples:
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|         sampler=DistributedSampler(dataset)  # NEW
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|     )
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|     return dataloader
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| 
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| 
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| #####################################
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| # Chapter 3
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| #####################################
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| class PyTorchMultiHeadAttention(nn.Module):
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|     def __init__(self, d_in, d_out, num_heads, dropout=0.0, qkv_bias=False):
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|         super().__init__()
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| 
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|         assert d_out % num_heads == 0, "embed_dim is indivisible by num_heads"
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| 
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|         self.num_heads = num_heads
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|         self.head_dim = d_out // num_heads
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|         self.d_out = d_out
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| 
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|         self.qkv = nn.Linear(d_in, 3 * d_out, bias=qkv_bias)
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|         self.proj = nn.Linear(d_out, d_out)
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|         self.dropout = dropout
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| 
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|     def forward(self, x):
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|         batch_size, num_tokens, embed_dim = x.shape
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| 
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|         # (b, num_tokens, embed_dim) --> (b, num_tokens, 3 * embed_dim)
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|         qkv = self.qkv(x)
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| 
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|         # (b, num_tokens, 3 * embed_dim) --> (b, num_tokens, 3, num_heads, head_dim)
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|         qkv = qkv.view(batch_size, num_tokens, 3, self.num_heads, self.head_dim)
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| 
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|         # (b, num_tokens, 3, num_heads, head_dim) --> (3, b, num_heads, num_tokens, head_dim)
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|         qkv = qkv.permute(2, 0, 3, 1, 4)
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| 
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|         # (3, b, num_heads, num_tokens, head_dim) -> 3 times (b, num_heads, num_tokens, head_dim)
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|         queries, keys, values = qkv
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| 
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|         use_dropout = 0. if not self.training else self.dropout
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| 
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|         context_vec = nn.functional.scaled_dot_product_attention(
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|             queries, keys, values, attn_mask=None, dropout_p=use_dropout, is_causal=True)
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| 
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|         # Combine heads, where self.d_out = self.num_heads * self.head_dim
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|         context_vec = context_vec.transpose(1, 2).contiguous().view(batch_size, num_tokens, self.d_out)
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| 
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|         context_vec = self.proj(context_vec)
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| 
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|         return context_vec
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| 
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| 
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| #####################################
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| # Chapter 4
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| #####################################
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| 
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| 
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| class FeedForward(nn.Module):
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|     def __init__(self, cfg):
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|         super().__init__()
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|         self.layers = nn.Sequential(
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|             nn.Linear(cfg["emb_dim"], 4 * cfg["emb_dim"]),
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|             nn.GELU(approximate="tanh"),
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|             nn.Linear(4 * cfg["emb_dim"], cfg["emb_dim"]),
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|         )
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| 
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|     def forward(self, x):
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|         return self.layers(x)
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| 
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| 
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| class TransformerBlock(nn.Module):
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|     def __init__(self, cfg):
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|         super().__init__()
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|         self.att = PyTorchMultiHeadAttention(
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|             d_in=cfg["emb_dim"],
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|             d_out=cfg["emb_dim"],
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|             num_heads=cfg["n_heads"],
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|             dropout=cfg["drop_rate"],
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|             qkv_bias=cfg["qkv_bias"])
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|         self.ff = FeedForward(cfg)
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|         self.norm1 = nn.LayerNorm(cfg["emb_dim"])
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|         self.norm2 = nn.LayerNorm(cfg["emb_dim"])
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|         self.drop_shortcut = nn.Dropout(cfg["drop_rate"])
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| 
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|     def forward(self, x):
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|         # Shortcut connection for attention block
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|         shortcut = x
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|         x = self.norm1(x)
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|         x = self.att(x)   # Shape [batch_size, num_tokens, emb_size]
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|         x = self.drop_shortcut(x)
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|         x = x + shortcut  # Add the original input back
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| 
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|         # Shortcut connection for feed-forward block
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|         shortcut = x
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|         x = self.norm2(x)
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|         x = self.ff(x)
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|         x = self.drop_shortcut(x)
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|         x = x + shortcut  # Add the original input back
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| 
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|         return x
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| 
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| 
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| class GPTModel(nn.Module):
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|     def __init__(self, cfg):
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|         super().__init__()
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|         self.tok_emb = nn.Embedding(cfg["vocab_size"], cfg["emb_dim"])
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|         self.pos_emb = nn.Embedding(cfg["context_length"], cfg["emb_dim"])
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|         self.drop_emb = nn.Dropout(cfg["drop_rate"])
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| 
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|         self.trf_blocks = nn.Sequential(
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|             *[TransformerBlock(cfg) for _ in range(cfg["n_layers"])])
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| 
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|         self.final_norm = nn.LayerNorm(cfg["emb_dim"])
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|         self.out_head = nn.Linear(cfg["emb_dim"], cfg["vocab_size"], bias=False)
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| 
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|     def forward(self, in_idx):
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|         batch_size, seq_len = in_idx.shape
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|         tok_embeds = self.tok_emb(in_idx)
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|         pos_embeds = self.pos_emb(torch.arange(seq_len, device=in_idx.device))
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|         x = tok_embeds + pos_embeds  # Shape [batch_size, num_tokens, emb_size]
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|         x = self.drop_emb(x)
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|         x = self.trf_blocks(x)
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|         x = self.final_norm(x)
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|         logits = self.out_head(x)
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|         return logits
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| 
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| 
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| def generate_text_simple(model, idx, max_new_tokens, context_size):
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|     # idx is (B, T) array of indices in the current context
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|     for _ in range(max_new_tokens):
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| 
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|         # Crop current context if it exceeds the supported context size
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|         # E.g., if LLM supports only 5 tokens, and the context size is 10
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|         # then only the last 5 tokens are used as context
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|         idx_cond = idx[:, -context_size:]
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| 
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|         # Get the predictions
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|         with torch.no_grad():
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|             logits = model(idx_cond)
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| 
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|         # Focus only on the last time step
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|         # (batch, n_token, vocab_size) becomes (batch, vocab_size)
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|         logits = logits[:, -1, :]
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| 
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|         # Get the idx of the vocab entry with the highest logits value
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|         idx_next = torch.argmax(logits, dim=-1, keepdim=True)  # (batch, 1)
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| 
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|         # Append sampled index to the running sequence
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|         idx = torch.cat((idx, idx_next), dim=1)  # (batch, n_tokens+1)
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| 
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|     return idx
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| 
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| #####################################
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| # Chapter 5
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| #####################################
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| 
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| 
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| def text_to_token_ids(text, tokenizer):
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|     encoded = tokenizer.encode(text)
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|     encoded_tensor = torch.tensor(encoded).unsqueeze(0)  # add batch dimension
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|     return encoded_tensor
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| 
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| 
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| def token_ids_to_text(token_ids, tokenizer):
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|     flat = token_ids.squeeze(0)  # remove batch dimension
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|     return tokenizer.decode(flat.tolist())
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| 
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| 
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| def calc_loss_batch(input_batch, target_batch, model, device):
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|     input_batch, target_batch = input_batch.to(device), target_batch.to(device)
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|     logits = model(input_batch)
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|     loss = torch.nn.functional.cross_entropy(logits.flatten(0, 1), target_batch.flatten())
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|     return loss
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| 
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| 
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| def calc_loss_loader(data_loader, model, device, num_batches=None):
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|     total_loss = 0.
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|     if len(data_loader) == 0:
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|         return float("nan")
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|     elif num_batches is None:
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|         num_batches = len(data_loader)
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|     else:
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|         num_batches = min(num_batches, len(data_loader))
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|     for i, (input_batch, target_batch) in enumerate(data_loader):
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|         if i < num_batches:
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|             loss = calc_loss_batch(input_batch, target_batch, model, device)
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|             total_loss += loss.item()
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|         else:
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|             break
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|     return total_loss / num_batches
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| 
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| 
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| def evaluate_model(model, train_loader, val_loader, device, eval_iter):
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|     model.eval()
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|     with torch.no_grad():
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|         train_loss = calc_loss_loader(train_loader, model, device, num_batches=eval_iter)
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|         val_loss = calc_loss_loader(val_loader, model, device, num_batches=eval_iter)
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|     model.train()
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|     return train_loss, val_loss
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| 
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| 
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| def generate_and_print_sample(model, device, start_context):
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|     model.eval()
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| 
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|     # NEW: Modify for DDP
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|     context_size = model.module.pos_emb.weight.shape[0] if isinstance(model, DDP) else model.pos_emb.weight.shape[0]
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|     encoded = text_to_token_ids(start_context, tiktoken.get_encoding("gpt2")).to(device)
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|     with torch.no_grad():
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|         token_ids = generate_text_simple(
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|             model=model, idx=encoded,
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|             max_new_tokens=50, context_size=context_size
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|         )
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|         decoded_text = token_ids_to_text(token_ids, tiktoken.get_encoding("gpt2"))
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|         print(decoded_text.replace("\n", " "))  # Compact print format
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|     model.train()
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| 
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| 
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| def train_model_simple_with_timing(model, train_loader, val_loader, optimizer, device,
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|                                    num_epochs, eval_freq, eval_iter, start_context, tokenizer):
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|     train_losses, val_losses, track_tokens = [], [], []
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|     total_tokens, global_step, last_tokens = 0, -1, 0
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| 
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|     # NEW: Determine the current rank (default to 0 if not distributed)
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|     rank = torch.distributed.get_rank() if torch.distributed.is_initialized() else 0
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|     # world_size = torch.distributed.get_world_size() if torch.distributed.is_initialized() else 1
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| 
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|     # Variables for cumulative average tokens/sec
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|     cumulative_tokens, cumulative_time = 0.0, 0.0
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| 
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|     # CUDA-specific timing setup
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|     use_cuda = device.type == "cuda"
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|     if use_cuda:
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|         t_start = torch.cuda.Event(enable_timing=True)
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|         t_end = torch.cuda.Event(enable_timing=True)
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|         torch.cuda.synchronize()  # Ensure all prior CUDA operations are done
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|         t_start.record()          # Start the timer for the first interval
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|     else:
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|         t0 = time.time()          # Start the timer for the first interval
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| 
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|     # Main training loop
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|     for epoch in range(num_epochs):
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|         # NEW: set epoch for DistributedSampler so each process gets a unique shuffle order
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|         if isinstance(train_loader.sampler, DistributedSampler):
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|             train_loader.sampler.set_epoch(epoch)
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| 
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|         model.train()
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|         for inp_batch, tgt_batch in train_loader:
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|             optimizer.zero_grad()
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|             global_step += 1
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| 
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|             # Forward and backward pass
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|             loss = calc_loss_batch(inp_batch, tgt_batch, model, device)
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|             loss.backward()
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|             optimizer.step()
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| 
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|             total_tokens += inp_batch.numel()
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| 
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|             # At evaluation intervals, measure elapsed time and tokens per second
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|             if global_step % eval_freq == 0:
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|                 # End timing for the current interval
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|                 if use_cuda:
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|                     t_end.record()
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|                     torch.cuda.synchronize()  # Wait for all CUDA ops to complete.
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|                     elapsed = t_start.elapsed_time(t_end) / 1000  # Convert ms to seconds
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|                     t_start.record()  # Reset timer for the next interval
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|                 else:
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|                     elapsed = time.time() - t0
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|                     t0 = time.time()  # Reset timer for the next interval
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| 
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|                 # Calculate local tokens processed during this interval
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|                 local_interval = total_tokens - last_tokens
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|                 last_tokens = total_tokens
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| 
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|                 # Aggregate the tokens processed over all devices
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|                 local_tensor = torch.tensor([local_interval], device=device, dtype=torch.float)
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|                 global_tensor = local_tensor.clone()
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|                 torch.distributed.all_reduce(global_tensor, op=torch.distributed.ReduceOp.SUM)
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|                 global_interval = global_tensor.item()
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| 
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|                 # Global tokens per second for this interval
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|                 global_tps = global_interval / elapsed if elapsed > 0 else 0
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| 
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|                 # Update cumulative tokens (local) and aggregate globally
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|                 cumulative_tokens += local_interval
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|                 local_cum_tensor = torch.tensor([cumulative_tokens], device=device, dtype=torch.float)
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|                 global_cum_tensor = local_cum_tensor.clone()
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|                 torch.distributed.all_reduce(global_cum_tensor, op=torch.distributed.ReduceOp.SUM)
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|                 global_cumulative_tokens = global_cum_tensor.item()
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|                 cumulative_time += elapsed
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|                 global_avg_tps = global_cumulative_tokens / cumulative_time if cumulative_time > 0 else 0
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| 
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|                 # Evaluate model performance (this may add overhead)
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|                 train_loss, val_loss = evaluate_model(model, train_loader, val_loader, device, eval_iter)
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|                 train_losses.append(train_loss)
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|                 val_losses.append(val_loss)
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|                 track_tokens.append(total_tokens)
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| 
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|                 # NEW: Only print logs once per GPU (choosing the rank 0 GPU)
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|                 if rank == 0:
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|                     print(f"Ep {epoch+1}, Step {global_step:06d}, "
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|                           f"Train: {train_loss:.3f}, Val: {val_loss:.3f}, "
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|                           f"Step tok/sec: {round(global_tps)}, Global avg tok/sec: {round(global_avg_tps)}")
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| 
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|         # NEW Only rank 0 prints the generated sample and memory usage stats
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|         if rank == 0 and epoch % 5 == 0:
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|             generate_and_print_sample(model, device, start_context)
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| 
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|             # Memory stats
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|             if torch.cuda.is_available():
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|                 current_device = torch.cuda.current_device()
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|                 allocated = torch.cuda.memory_allocated(current_device) / 1024**3  # Convert to GB
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|                 reserved = torch.cuda.memory_reserved(current_device) / 1024**3    # Convert to GB
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| 
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|                 print(f"\nAllocated memory: {allocated:.4f} GB")
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|                 print(f"Reserved memory: {reserved:.4f} GB\n")
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| 
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|     return train_losses, val_losses, track_tokens
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| 
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| 
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| def plot_losses(epochs_seen, tokens_seen, train_losses, val_losses):
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|     fig, ax1 = plt.subplots()
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| 
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|     # Plot training and validation loss against epochs
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|     ax1.plot(epochs_seen, train_losses, label="Training loss")
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|     ax1.plot(epochs_seen, val_losses, linestyle="-.", label="Validation loss")
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|     ax1.set_xlabel("Epochs")
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|     ax1.set_ylabel("Loss")
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|     ax1.legend(loc="upper right")
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| 
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|     # Create a second x-axis for tokens seen
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|     ax2 = ax1.twiny()  # Create a second x-axis that shares the same y-axis
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|     ax2.plot(tokens_seen, train_losses, alpha=0)  # Invisible plot for aligning ticks
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|     ax2.set_xlabel("Tokens seen")
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| 
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|     fig.tight_layout()  # Adjust layout to make room
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|     # plt.show()
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| 
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| 
 | |
| #####################################
 | |
| # Main function calls
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| #####################################
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| 
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| # NEW: Add rank and world_size
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| def main(gpt_config, settings, rank, world_size):
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| 
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|     ddp_setup(rank, world_size)  # NEW: initialize process groups
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|     device = torch.device("cuda", rank)
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| 
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|     torch.manual_seed(123)
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| 
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|     # NEW: Print info only on 1 GPU
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|     if rank == 0:
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|         print(f"PyTorch version: {torch.__version__}")
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|         if torch.cuda.is_available():
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|             print(f"CUDA version: {torch.version.cuda}")
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| 
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|             capability = torch.cuda.get_device_capability()
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|             if capability[0] >= 7:  # Volta (7.0+), Turing (7.5+), Ampere (8.0+), Hopper (9.0+)
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|                 torch.set_float32_matmul_precision("high")
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|                 print("Uses tensor cores")
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|             else:
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|                 print("Tensor cores not supported on this GPU. Using default precision.")
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|         print()
 | |
| 
 | |
|     ##############################
 | |
|     # Download data if necessary
 | |
|     ##############################
 | |
| 
 | |
|     file_path = "middlemarch.txt"
 | |
|     url = "https://www.gutenberg.org/cache/epub/145/pg145.txt"
 | |
| 
 | |
|     # NEW: Only download 1 time
 | |
|     if rank == 0:
 | |
|         if not os.path.exists(file_path):
 | |
|             with urllib.request.urlopen(url) as response:
 | |
|                 text_data = response.read().decode('utf-8')
 | |
|             with open(file_path, "w", encoding="utf-8") as file:
 | |
|                 file.write(text_data)
 | |
| 
 | |
|     # NEW: All processes wait until rank 0 is done, using the GPU index.
 | |
|     torch.distributed.barrier(device_ids=[device.index])
 | |
| 
 | |
|     with open(file_path, "r", encoding="utf-8") as file:
 | |
|         text_data = file.read()
 | |
| 
 | |
|     ##############################
 | |
|     # Initialize model
 | |
|     ##############################
 | |
| 
 | |
|     model = GPTModel(gpt_config)
 | |
|     model = torch.compile(model)
 | |
|     model = model.to(device)
 | |
|     model = model.to(torch.bfloat16)
 | |
|     # NEW: Wrap model with DDP
 | |
|     model = DDP(model, device_ids=[rank])
 | |
|     optimizer = torch.optim.AdamW(
 | |
|         model.parameters(), lr=settings["learning_rate"], weight_decay=settings["weight_decay"],
 | |
|         fused=True
 | |
|     )
 | |
| 
 | |
|     ##############################
 | |
|     # Set up dataloaders
 | |
|     ##############################
 | |
| 
 | |
|     # Train/validation ratio
 | |
|     train_ratio = 0.90
 | |
|     split_idx = int(train_ratio * len(text_data))
 | |
| 
 | |
|     train_loader = create_dataloader_v1(
 | |
|         text_data[:split_idx],
 | |
|         batch_size=settings["batch_size"],
 | |
|         max_length=gpt_config["context_length"],
 | |
|         stride=gpt_config["context_length"],
 | |
|         drop_last=True,
 | |
|         num_workers=4
 | |
|     )
 | |
| 
 | |
|     val_loader = create_dataloader_v1(
 | |
|         text_data[split_idx:],
 | |
|         batch_size=settings["batch_size"],
 | |
|         max_length=gpt_config["context_length"],
 | |
|         stride=gpt_config["context_length"],
 | |
|         drop_last=False,
 | |
|         num_workers=4
 | |
|     )
 | |
| 
 | |
|     ##############################
 | |
|     # Train model
 | |
|     ##############################
 | |
| 
 | |
|     tokenizer = tiktoken.get_encoding("gpt2")
 | |
| 
 | |
|     train_losses, val_losses, tokens_seen = train_model_simple_with_timing(
 | |
|         model=model,
 | |
|         train_loader=train_loader,
 | |
|         val_loader=val_loader,
 | |
|         optimizer=optimizer,
 | |
|         device=device,
 | |
|         num_epochs=settings["num_epochs"],
 | |
|         eval_freq=5,
 | |
|         eval_iter=1,
 | |
|         start_context="Every effort moves you",
 | |
|         tokenizer=tokenizer
 | |
|     )
 | |
| 
 | |
|     # NEW: Clean up distributed processes
 | |
|     destroy_process_group()
 | |
| 
 | |
|     return train_losses, val_losses, tokens_seen, model
 | |
| 
 | |
| 
 | |
| if __name__ == "__main__":
 | |
| 
 | |
|     # NEW: Extract rank and world size from environment variables
 | |
|     if "WORLD_SIZE" in os.environ:
 | |
|         world_size = int(os.environ["WORLD_SIZE"])
 | |
|     else:
 | |
|         world_size = 1
 | |
| 
 | |
|     if "LOCAL_RANK" in os.environ:
 | |
|         rank = int(os.environ["LOCAL_RANK"])
 | |
|     elif "RANK" in os.environ:
 | |
|         rank = int(os.environ["RANK"])
 | |
|     else:
 | |
|         rank = 0
 | |
| 
 | |
|     GPT_CONFIG_124M = {
 | |
|         "vocab_size": 50304,     # Vocabulary size
 | |
|         "context_length": 1024,  # Input tokens per training example
 | |
|         "emb_dim": 768,          # Embedding dimension
 | |
|         "n_heads": 12,           # Number of attention heads
 | |
|         "n_layers": 12,          # Number of layers
 | |
|         "drop_rate": 0.1,        # Dropout rate
 | |
|         "qkv_bias": False        # Query-key-value bias
 | |
|     }
 | |
| 
 | |
|     OTHER_SETTINGS = {
 | |
|         "learning_rate": 5e-4,  # * world_size,  # NEW: Increase learning rate to account for multiple GPUs
 | |
|         "num_epochs": 50,
 | |
|         "batch_size": 32,
 | |
|         "weight_decay": 0.1
 | |
|     }
 | |
| 
 | |
|     ###########################
 | |
|     # Initiate training
 | |
|     ###########################
 | |
| 
 | |
|     train_losses, val_losses, tokens_seen, model = main(
 | |
|         GPT_CONFIG_124M, OTHER_SETTINGS,
 | |
|         rank, world_size  # NEW
 | |
|     )
 | |
| 
 | |
|     ###########################
 | |
|     # After training
 | |
|     ###########################
 | |
| 
 | |
|     # NEW: Only create 1 plot
 | |
|     if rank == 0:
 | |
|         # Plot results
 | |
|         epochs_tensor = torch.linspace(0, OTHER_SETTINGS["num_epochs"], len(train_losses))
 | |
|         plot_losses(epochs_tensor, tokens_seen, train_losses, val_losses)
 | |
|         plt.savefig("loss.pdf")
 | |
| 
 | |
|     # Save and load model
 | |
|     #
 | |
|     # compiled = hasattr(model, "_orig_mod")
 | |
|     # if compiled:
 | |
|     #     torch.save(model._orig_mod.state_dict(), "model.pth")
 | |
|     # else:
 | |
|     #     torch.save(model.state_dict(), "model.pth")
 | |
|     #
 | |
|     # model = GPTModel(GPT_CONFIG_124M)
 | |
|     # model.load_state_dict(torch.load("model.pth", weights_only=True))
 | 
