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	* updated .gitignore * removed unused GELU import * fixed model_configs, fixed all tensors on same device * removed unused tiktoken * update * update hparam search * remove redundant tokenizer argument --------- Co-authored-by: rasbt <mail@sebastianraschka.com>
		
			
				
	
	
		
			542 lines
		
	
	
		
			20 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
			
		
		
	
	
			542 lines
		
	
	
		
			20 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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# This file collects all the relevant code that we covered thus far
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# throughout Chapters 2-6.
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# This file can be run as a standalone script.
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import os
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from pathlib import Path
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import urllib
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import zipfile
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import matplotlib.pyplot as plt
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import numpy as np
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import pandas as pd
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import tiktoken
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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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#####################################
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# Chapter 2
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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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        # Tokenize the entire text
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        token_ids = tokenizer.encode(txt, allowed_special={"<|endoftext|>"})
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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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    def __len__(self):
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        return len(self.input_ids)
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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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def create_dataloader_v1(txt, batch_size=4, max_length=256,
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                         stride=128, shuffle=True, drop_last=True):
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    # Initialize the tokenizer
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    tokenizer = tiktoken.get_encoding("gpt2")
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    # Create dataset
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    dataset = GPTDatasetV1(txt, tokenizer, max_length, stride)
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    # Create dataloader
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    dataloader = DataLoader(
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        dataset, batch_size=batch_size, shuffle=shuffle, drop_last=drop_last)
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    return dataloader
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#####################################
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# Chapter 3
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#####################################
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class MultiHeadAttention(nn.Module):
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    def __init__(self, d_in, d_out, context_length, dropout, num_heads, qkv_bias=False):
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        super().__init__()
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        assert d_out % num_heads == 0, "d_out must be divisible by n_heads"
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        self.d_out = d_out
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        self.num_heads = num_heads
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        self.head_dim = d_out // num_heads  # Reduce the projection dim to match desired output dim
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        self.W_query = nn.Linear(d_in, d_out, bias=qkv_bias)
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        self.W_key = nn.Linear(d_in, d_out, bias=qkv_bias)
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        self.W_value = nn.Linear(d_in, d_out, bias=qkv_bias)
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        self.out_proj = nn.Linear(d_out, d_out)  # Linear layer to combine head outputs
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        self.dropout = nn.Dropout(dropout)
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        self.register_buffer('mask', torch.triu(torch.ones(context_length, context_length), diagonal=1))
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    def forward(self, x):
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        b, num_tokens, d_in = x.shape
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        keys = self.W_key(x)  # Shape: (b, num_tokens, d_out)
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        queries = self.W_query(x)
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        values = self.W_value(x)
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        # We implicitly split the matrix by adding a `num_heads` dimension
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        # Unroll last dim: (b, num_tokens, d_out) -> (b, num_tokens, num_heads, head_dim)
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        keys = keys.view(b, num_tokens, self.num_heads, self.head_dim)
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        values = values.view(b, num_tokens, self.num_heads, self.head_dim)
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        queries = queries.view(b, num_tokens, self.num_heads, self.head_dim)
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        # Transpose: (b, num_tokens, num_heads, head_dim) -> (b, num_heads, num_tokens, head_dim)
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        keys = keys.transpose(1, 2)
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        queries = queries.transpose(1, 2)
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        values = values.transpose(1, 2)
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        # Compute scaled dot-product attention (aka self-attention) with a causal mask
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        attn_scores = queries @ keys.transpose(2, 3)  # Dot product for each head
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        # Original mask truncated to the number of tokens and converted to boolean
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        mask_bool = self.mask.bool()[:num_tokens, :num_tokens]
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        # Use the mask to fill attention scores
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        attn_scores.masked_fill_(mask_bool, -torch.inf)
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        attn_weights = torch.softmax(attn_scores / keys.shape[-1]**0.5, dim=-1)
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        attn_weights = self.dropout(attn_weights)
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        # Shape: (b, num_tokens, num_heads, head_dim)
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        context_vec = (attn_weights @ values).transpose(1, 2)
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        # Combine heads, where self.d_out = self.num_heads * self.head_dim
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        context_vec = context_vec.reshape(b, num_tokens, self.d_out)
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        context_vec = self.out_proj(context_vec)  # optional projection
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        return context_vec
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#####################################
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# Chapter 4
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#####################################
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class LayerNorm(nn.Module):
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    def __init__(self, emb_dim):
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        super().__init__()
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        self.eps = 1e-5
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        self.scale = nn.Parameter(torch.ones(emb_dim))
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        self.shift = nn.Parameter(torch.zeros(emb_dim))
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    def forward(self, x):
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        mean = x.mean(dim=-1, keepdim=True)
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        var = x.var(dim=-1, keepdim=True, unbiased=False)
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        norm_x = (x - mean) / torch.sqrt(var + self.eps)
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        return self.scale * norm_x + self.shift
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class GELU(nn.Module):
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    def __init__(self):
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        super().__init__()
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    def forward(self, x):
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        return 0.5 * x * (1 + torch.tanh(
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            torch.sqrt(torch.tensor(2.0 / torch.pi)) *
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            (x + 0.044715 * torch.pow(x, 3))
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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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            GELU(),
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            nn.Linear(4 * cfg["emb_dim"], cfg["emb_dim"]),
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        )
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    def forward(self, x):
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        return self.layers(x)
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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 = MultiHeadAttention(
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            d_in=cfg["emb_dim"],
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            d_out=cfg["emb_dim"],
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            context_length=cfg["context_length"],
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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 = LayerNorm(cfg["emb_dim"])
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        self.norm2 = LayerNorm(cfg["emb_dim"])
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        self.drop_resid = nn.Dropout(cfg["drop_rate"])
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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_resid(x)
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        x = x + shortcut  # Add the original input back
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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_resid(x)
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        x = x + shortcut  # Add the original input back
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        return x
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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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        self.trf_blocks = nn.Sequential(
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            *[TransformerBlock(cfg) for _ in range(cfg["n_layers"])])
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        self.final_norm = 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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    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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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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        # 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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        # Get the predictions
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        with torch.no_grad():
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            logits = model(idx_cond)
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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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        # 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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        # 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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    return idx
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#####################################
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# Chapter 5
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#####################################
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def assign(left, right):
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    if left.shape != right.shape:
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        raise ValueError(f"Shape mismatch. Left: {left.shape}, Right: {right.shape}")
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    return torch.nn.Parameter(torch.tensor(right))
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def load_weights_into_gpt(gpt, params):
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    gpt.pos_emb.weight = assign(gpt.pos_emb.weight, params['wpe'])
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    gpt.tok_emb.weight = assign(gpt.tok_emb.weight, params['wte'])
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    for b in range(len(params["blocks"])):
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        q_w, k_w, v_w = np.split(
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            (params["blocks"][b]["attn"]["c_attn"])["w"], 3, axis=-1)
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        gpt.trf_blocks[b].att.W_query.weight = assign(
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            gpt.trf_blocks[b].att.W_query.weight, q_w.T)
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        gpt.trf_blocks[b].att.W_key.weight = assign(
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            gpt.trf_blocks[b].att.W_key.weight, k_w.T)
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        gpt.trf_blocks[b].att.W_value.weight = assign(
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            gpt.trf_blocks[b].att.W_value.weight, v_w.T)
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        q_b, k_b, v_b = np.split(
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            (params["blocks"][b]["attn"]["c_attn"])["b"], 3, axis=-1)
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        gpt.trf_blocks[b].att.W_query.bias = assign(
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            gpt.trf_blocks[b].att.W_query.bias, q_b)
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        gpt.trf_blocks[b].att.W_key.bias = assign(
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            gpt.trf_blocks[b].att.W_key.bias, k_b)
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        gpt.trf_blocks[b].att.W_value.bias = assign(
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            gpt.trf_blocks[b].att.W_value.bias, v_b)
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        gpt.trf_blocks[b].att.out_proj.weight = assign(
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            gpt.trf_blocks[b].att.out_proj.weight,
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            params["blocks"][b]["attn"]["c_proj"]["w"].T)
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        gpt.trf_blocks[b].att.out_proj.bias = assign(
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            gpt.trf_blocks[b].att.out_proj.bias,
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            params["blocks"][b]["attn"]["c_proj"]["b"])
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        gpt.trf_blocks[b].ff.layers[0].weight = assign(
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            gpt.trf_blocks[b].ff.layers[0].weight,
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            params["blocks"][b]["mlp"]["c_fc"]["w"].T)
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        gpt.trf_blocks[b].ff.layers[0].bias = assign(
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            gpt.trf_blocks[b].ff.layers[0].bias,
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            params["blocks"][b]["mlp"]["c_fc"]["b"])
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        gpt.trf_blocks[b].ff.layers[2].weight = assign(
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            gpt.trf_blocks[b].ff.layers[2].weight,
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            params["blocks"][b]["mlp"]["c_proj"]["w"].T)
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        gpt.trf_blocks[b].ff.layers[2].bias = assign(
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            gpt.trf_blocks[b].ff.layers[2].bias,
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            params["blocks"][b]["mlp"]["c_proj"]["b"])
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        gpt.trf_blocks[b].norm1.scale = assign(
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            gpt.trf_blocks[b].norm1.scale,
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            params["blocks"][b]["ln_1"]["g"])
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        gpt.trf_blocks[b].norm1.shift = assign(
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            gpt.trf_blocks[b].norm1.shift,
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            params["blocks"][b]["ln_1"]["b"])
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        gpt.trf_blocks[b].norm2.scale = assign(
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            gpt.trf_blocks[b].norm2.scale,
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            params["blocks"][b]["ln_2"]["g"])
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        gpt.trf_blocks[b].norm2.shift = assign(
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            gpt.trf_blocks[b].norm2.shift,
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            params["blocks"][b]["ln_2"]["b"])
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    gpt.final_norm.scale = assign(gpt.final_norm.scale, params["g"])
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    gpt.final_norm.shift = assign(gpt.final_norm.shift, params["b"])
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    gpt.out_head.weight = assign(gpt.out_head.weight, params["wte"])
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def text_to_token_ids(text, tokenizer):
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    encoded = tokenizer.encode(text, allowed_special={'<|endoftext|>'})
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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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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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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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        # Reduce the number of batches to match the total number of batches in the data loader
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        # if num_batches exceeds the number of batches in the data loader
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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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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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# Chapter 6
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#####################################
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def download_and_unzip_spam_data(url, zip_path, extracted_path, data_file_path):
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    if data_file_path.exists():
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        print(f"{data_file_path} already exists. Skipping download and extraction.")
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        return
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    # Downloading the file
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    with urllib.request.urlopen(url) as response:
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        with open(zip_path, "wb") as out_file:
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            out_file.write(response.read())
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    # Unzipping the file
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    with zipfile.ZipFile(zip_path, "r") as zip_ref:
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        zip_ref.extractall(extracted_path)
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    # Add .tsv file extension
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    original_file_path = Path(extracted_path) / "SMSSpamCollection"
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    os.rename(original_file_path, data_file_path)
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    print(f"File downloaded and saved as {data_file_path}")
 | 
						|
 | 
						|
 | 
						|
def create_balanced_dataset(df):
 | 
						|
 | 
						|
    # Count the instances of "spam"
 | 
						|
    num_spam = df[df["Label"] == "spam"].shape[0]
 | 
						|
 | 
						|
    # Randomly sample "ham' instances to match the number of 'spam' instances
 | 
						|
    ham_subset = df[df["Label"] == "ham"].sample(num_spam, random_state=123)
 | 
						|
 | 
						|
    # Combine ham "subset" with "spam"
 | 
						|
    balanced_df = pd.concat([ham_subset, df[df["Label"] == "spam"]])
 | 
						|
 | 
						|
    return balanced_df
 | 
						|
 | 
						|
 | 
						|
def random_split(df, train_frac, validation_frac):
 | 
						|
    # Shuffle the entire DataFrame
 | 
						|
    df = df.sample(frac=1, random_state=123).reset_index(drop=True)
 | 
						|
 | 
						|
    # Calculate split indices
 | 
						|
    train_end = int(len(df) * train_frac)
 | 
						|
    validation_end = train_end + int(len(df) * validation_frac)
 | 
						|
 | 
						|
    # Split the DataFrame
 | 
						|
    train_df = df[:train_end]
 | 
						|
    validation_df = df[train_end:validation_end]
 | 
						|
    test_df = df[validation_end:]
 | 
						|
 | 
						|
    return train_df, validation_df, test_df
 | 
						|
 | 
						|
 | 
						|
class SpamDataset(Dataset):
 | 
						|
    def __init__(self, csv_file, tokenizer, max_length=None, pad_token_id=50256):
 | 
						|
        self.data = pd.read_csv(csv_file)
 | 
						|
 | 
						|
        # Pre-tokenize texts
 | 
						|
        self.encoded_texts = [
 | 
						|
            tokenizer.encode(text) for text in self.data["Text"]
 | 
						|
        ]
 | 
						|
 | 
						|
        if max_length is None:
 | 
						|
            self.max_length = self._longest_encoded_length()
 | 
						|
        else:
 | 
						|
            self.max_length = max_length
 | 
						|
            # Truncate sequences if they are longer than max_length
 | 
						|
            self.encoded_texts = [
 | 
						|
                encoded_text[:self.max_length]
 | 
						|
                for encoded_text in self.encoded_texts
 | 
						|
            ]
 | 
						|
 | 
						|
        # Pad sequences to the longest sequence
 | 
						|
        self.encoded_texts = [
 | 
						|
            encoded_text + [pad_token_id] * (self.max_length - len(encoded_text))
 | 
						|
            for encoded_text in self.encoded_texts
 | 
						|
        ]
 | 
						|
 | 
						|
    def __getitem__(self, index):
 | 
						|
        encoded = self.encoded_texts[index]
 | 
						|
        label = self.data.iloc[index]["Label"]
 | 
						|
        return torch.tensor(encoded, dtype=torch.long), torch.tensor(label, dtype=torch.long)
 | 
						|
 | 
						|
    def __len__(self):
 | 
						|
        return len(self.data)
 | 
						|
 | 
						|
    def _longest_encoded_length(self):
 | 
						|
        max_length = 0
 | 
						|
        for encoded_text in self.encoded_texts:
 | 
						|
            encoded_length = len(encoded_text)
 | 
						|
            if encoded_length > max_length:
 | 
						|
                max_length = encoded_length
 | 
						|
        return max_length
 | 
						|
 | 
						|
 | 
						|
@torch.no_grad()  # Disable gradient tracking for efficiency
 | 
						|
def calc_accuracy_loader(data_loader, model, device, num_batches=None):
 | 
						|
    model.eval()
 | 
						|
    correct_predictions, num_examples = 0, 0
 | 
						|
 | 
						|
    if num_batches is None:
 | 
						|
        num_batches = len(data_loader)
 | 
						|
    else:
 | 
						|
        num_batches = min(num_batches, len(data_loader))
 | 
						|
    for i, (input_batch, target_batch) in enumerate(data_loader):
 | 
						|
        if i < num_batches:
 | 
						|
            input_batch, target_batch = input_batch.to(device), target_batch.to(device)
 | 
						|
            logits = model(input_batch)[:, -1, :]  # Logits of last output token
 | 
						|
            predicted_labels = torch.argmax(logits, dim=-1)
 | 
						|
 | 
						|
            num_examples += predicted_labels.shape[0]
 | 
						|
            correct_predictions += (predicted_labels == target_batch).sum().item()
 | 
						|
        else:
 | 
						|
            break
 | 
						|
    return correct_predictions / num_examples
 | 
						|
 | 
						|
 | 
						|
def calc_loss_batch(input_batch, target_batch, model, device):
 | 
						|
    input_batch, target_batch = input_batch.to(device), target_batch.to(device)
 | 
						|
    logits = model(input_batch)[:, -1, :]  # Logits of last output token
 | 
						|
    loss = torch.nn.functional.cross_entropy(logits, target_batch)
 | 
						|
    return loss
 | 
						|
 | 
						|
 | 
						|
# Overall the same as `train_model_simple` in chapter 5
 | 
						|
def train_classifier_simple(model, train_loader, val_loader, optimizer, device, num_epochs,
 | 
						|
                            eval_freq, eval_iter):
 | 
						|
    # Initialize lists to track losses and tokens seen
 | 
						|
    train_losses, val_losses, train_accs, val_accs = [], [], [], []
 | 
						|
    examples_seen, global_step = 0, -1
 | 
						|
 | 
						|
    # Main training loop
 | 
						|
    for epoch in range(num_epochs):
 | 
						|
        model.train()  # Set model to training mode
 | 
						|
 | 
						|
        for input_batch, target_batch in train_loader:
 | 
						|
            optimizer.zero_grad()  # Reset loss gradients from previous batch iteration
 | 
						|
            loss = calc_loss_batch(input_batch, target_batch, model, device)
 | 
						|
            loss.backward()  # Calculate loss gradients
 | 
						|
            optimizer.step()  # Update model weights using loss gradients
 | 
						|
            examples_seen += input_batch.shape[0]  # New: track examples instead of tokens
 | 
						|
            global_step += 1
 | 
						|
 | 
						|
            # Optional evaluation step
 | 
						|
            if global_step % eval_freq == 0:
 | 
						|
                train_loss, val_loss = evaluate_model(
 | 
						|
                    model, train_loader, val_loader, device, eval_iter)
 | 
						|
                train_losses.append(train_loss)
 | 
						|
                val_losses.append(val_loss)
 | 
						|
                print(f"Ep {epoch+1} (Step {global_step:06d}): "
 | 
						|
                      f"Train loss {train_loss:.3f}, Val loss {val_loss:.3f}")
 | 
						|
 | 
						|
        # Calculate accuracy after each epoch
 | 
						|
        train_accuracy = calc_accuracy_loader(train_loader, model, device, num_batches=eval_iter)
 | 
						|
        val_accuracy = calc_accuracy_loader(val_loader, model, device, num_batches=eval_iter)
 | 
						|
        print(f"Training accuracy: {train_accuracy*100:.2f}% | ", end="")
 | 
						|
        print(f"Validation accuracy: {val_accuracy*100:.2f}%")
 | 
						|
        train_accs.append(train_accuracy)
 | 
						|
        val_accs.append(val_accuracy)
 | 
						|
 | 
						|
    return train_losses, val_losses, train_accs, val_accs, examples_seen
 | 
						|
 | 
						|
 | 
						|
def plot_values(epochs_seen, examples_seen, train_values, val_values, label="loss"):
 | 
						|
    fig, ax1 = plt.subplots(figsize=(5, 3))
 | 
						|
 | 
						|
    # Plot training and validation loss against epochs
 | 
						|
    ax1.plot(epochs_seen, train_values, label=f"Training {label}")
 | 
						|
    ax1.plot(epochs_seen, val_values, linestyle="-.", label=f"Validation {label}")
 | 
						|
    ax1.set_xlabel("Epochs")
 | 
						|
    ax1.set_ylabel(label.capitalize())
 | 
						|
    ax1.legend()
 | 
						|
 | 
						|
    # Create a second x-axis for tokens seen
 | 
						|
    ax2 = ax1.twiny()  # Create a second x-axis that shares the same y-axis
 | 
						|
    ax2.plot(examples_seen, train_values, alpha=0)  # Invisible plot for aligning ticks
 | 
						|
    ax2.set_xlabel("Examples seen")
 | 
						|
 | 
						|
    fig.tight_layout()  # Adjust layout to make room
 | 
						|
    plt.savefig(f"{label}-plot.pdf")
 | 
						|
    plt.show()
 |