mirror of
https://github.com/frankwxu/AI4DigitalForensics.git
synced 2026-04-10 11:23:42 +00:00
269 lines
11 KiB
Plaintext
269 lines
11 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "71a7ed1e",
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"metadata": {},
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"source": [
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"# https://raw.githubusercontent.com/karpathy/ng-video-lecture/refs/heads/master/gpt.py\n",
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"# https://www.youtube.com/watch?v=kCc8FmEb1nY"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "28cdaf16",
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"metadata": {},
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"outputs": [],
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"source": [
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"import torch\n",
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"import torch.nn as nn\n",
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"from torch.nn import functional as F\n",
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"\n",
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"# hyperparameters\n",
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"batch_size = 64 # how many independent sequences will we process in parallel?\n",
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"block_size = 256 # what is the maximum context length for predictions?\n",
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"max_iters = 5000\n",
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"eval_interval = 500\n",
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"learning_rate = 3e-4\n",
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"device = 'cuda' if torch.cuda.is_available() else 'cpu'\n",
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"eval_iters = 200\n",
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"n_embd = 384\n",
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"n_head = 6\n",
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"n_layer = 6\n",
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"dropout = 0.2\n",
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"# ------------\n",
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"\n",
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"torch.manual_seed(1337)\n",
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"\n",
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"# wget https://raw.githubusercontent.com/karpathy/char-rnn/master/data/tinyshakespeare/input.txt\n",
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"with open('input.txt', 'r', encoding='utf-8') as f:\n",
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" text = f.read()\n",
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"\n",
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"# here are all the unique characters that occur in this text\n",
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"chars = sorted(list(set(text)))\n",
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"vocab_size = len(chars)\n",
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"# create a mapping from characters to integers\n",
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"stoi = { ch:i for i,ch in enumerate(chars) }\n",
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"itos = { i:ch for i,ch in enumerate(chars) }\n",
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"encode = lambda s: [stoi[c] for c in s] # encoder: take a string, output a list of integers\n",
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"decode = lambda l: ''.join([itos[i] for i in l]) # decoder: take a list of integers, output a string\n",
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"\n",
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"# Train and test splits\n",
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"data = torch.tensor(encode(text), dtype=torch.long)\n",
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"n = int(0.9*len(data)) # first 90% will be train, rest val\n",
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"train_data = data[:n]\n",
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"val_data = data[n:]\n",
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"\n",
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"# data loading\n",
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"def get_batch(split):\n",
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" # generate a small batch of data of inputs x and targets y\n",
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" data = train_data if split == 'train' else val_data\n",
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" ix = torch.randint(len(data) - block_size, (batch_size,))\n",
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" x = torch.stack([data[i:i+block_size] for i in ix])\n",
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" y = torch.stack([data[i+1:i+block_size+1] for i in ix])\n",
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" x, y = x.to(device), y.to(device)\n",
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" return x, y\n",
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"\n",
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"@torch.no_grad()\n",
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"def estimate_loss():\n",
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" out = {}\n",
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" model.eval()\n",
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" for split in ['train', 'val']:\n",
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" losses = torch.zeros(eval_iters)\n",
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" for k in range(eval_iters):\n",
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" X, Y = get_batch(split)\n",
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" logits, loss = model(X, Y)\n",
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" losses[k] = loss.item()\n",
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" out[split] = losses.mean()\n",
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" model.train()\n",
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" return out\n",
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"\n",
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"class Head(nn.Module):\n",
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" \"\"\" one head of self-attention \"\"\"\n",
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"\n",
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" def __init__(self, head_size):\n",
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" super().__init__()\n",
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" self.key = nn.Linear(n_embd, head_size, bias=False)\n",
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" self.query = nn.Linear(n_embd, head_size, bias=False)\n",
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" self.value = nn.Linear(n_embd, head_size, bias=False)\n",
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" self.register_buffer('tril', torch.tril(torch.ones(block_size, block_size)))\n",
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"\n",
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" self.dropout = nn.Dropout(dropout)\n",
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"\n",
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" def forward(self, x):\n",
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" # input of size (batch, time-step, channels)\n",
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" # output of size (batch, time-step, head size)\n",
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" B,T,C = x.shape\n",
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" k = self.key(x) # (B,T,hs)\n",
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" q = self.query(x) # (B,T,hs)\n",
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" # compute attention scores (\"affinities\")\n",
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" wei = q @ k.transpose(-2,-1) * k.shape[-1]**-0.5 # (B, T, hs) @ (B, hs, T) -> (B, T, T)\n",
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" wei = wei.masked_fill(self.tril[:T, :T] == 0, float('-inf')) # (B, T, T)\n",
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" wei = F.softmax(wei, dim=-1) # (B, T, T)\n",
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" wei = self.dropout(wei)\n",
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" # perform the weighted aggregation of the values\n",
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" v = self.value(x) # (B,T,hs)\n",
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" out = wei @ v # (B, T, T) @ (B, T, hs) -> (B, T, hs)\n",
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" return out\n",
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"\n",
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"class MultiHeadAttention(nn.Module):\n",
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" \"\"\" multiple heads of self-attention in parallel \"\"\"\n",
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"\n",
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" def __init__(self, num_heads, head_size):\n",
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" super().__init__()\n",
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" self.heads = nn.ModuleList([Head(head_size) for _ in range(num_heads)])\n",
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" self.proj = nn.Linear(head_size * num_heads, n_embd)\n",
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" self.dropout = nn.Dropout(dropout)\n",
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"\n",
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" def forward(self, x):\n",
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" out = torch.cat([h(x) for h in self.heads], dim=-1)\n",
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" out = self.dropout(self.proj(out))\n",
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" return out\n",
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"\n",
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"class FeedFoward(nn.Module):\n",
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" \"\"\" a simple linear layer followed by a non-linearity \"\"\"\n",
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"\n",
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" def __init__(self, n_embd):\n",
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" super().__init__()\n",
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" self.net = nn.Sequential(\n",
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" nn.Linear(n_embd, 4 * n_embd),\n",
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" nn.ReLU(),\n",
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" nn.Linear(4 * n_embd, n_embd),\n",
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" nn.Dropout(dropout),\n",
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" )\n",
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"\n",
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" def forward(self, x):\n",
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" return self.net(x)\n",
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"\n",
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"class Block(nn.Module):\n",
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" \"\"\" Transformer block: communication followed by computation \"\"\"\n",
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"\n",
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" def __init__(self, n_embd, n_head):\n",
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" # n_embd: embedding dimension, n_head: the number of heads we'd like\n",
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" super().__init__()\n",
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" head_size = n_embd // n_head\n",
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" self.sa = MultiHeadAttention(n_head, head_size)\n",
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" self.ffwd = FeedFoward(n_embd)\n",
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" self.ln1 = nn.LayerNorm(n_embd)\n",
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" self.ln2 = nn.LayerNorm(n_embd)\n",
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"\n",
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" def forward(self, x):\n",
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" x = x + self.sa(self.ln1(x))\n",
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" x = x + self.ffwd(self.ln2(x))\n",
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" return x\n",
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"\n",
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"class GPTLanguageModel(nn.Module):\n",
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"\n",
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" def __init__(self):\n",
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" super().__init__()\n",
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" # each token directly reads off the logits for the next token from a lookup table\n",
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" self.token_embedding_table = nn.Embedding(vocab_size, n_embd)\n",
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" self.position_embedding_table = nn.Embedding(block_size, n_embd)\n",
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" self.blocks = nn.Sequential(*[Block(n_embd, n_head=n_head) for _ in range(n_layer)])\n",
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" self.ln_f = nn.LayerNorm(n_embd) # final layer norm\n",
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" self.lm_head = nn.Linear(n_embd, vocab_size)\n",
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"\n",
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" # better init, not covered in the original GPT video, but important, will cover in followup video\n",
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" self.apply(self._init_weights)\n",
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"\n",
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" def _init_weights(self, module):\n",
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" if isinstance(module, nn.Linear):\n",
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" torch.nn.init.normal_(module.weight, mean=0.0, std=0.02)\n",
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" if module.bias is not None:\n",
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" torch.nn.init.zeros_(module.bias)\n",
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" elif isinstance(module, nn.Embedding):\n",
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" torch.nn.init.normal_(module.weight, mean=0.0, std=0.02)\n",
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"\n",
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" def forward(self, idx, targets=None):\n",
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" B, T = idx.shape\n",
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"\n",
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" # idx and targets are both (B,T) tensor of integers\n",
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" tok_emb = self.token_embedding_table(idx) # (B,T,C)\n",
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" pos_emb = self.position_embedding_table(torch.arange(T, device=device)) # (T,C)\n",
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" x = tok_emb + pos_emb # (B,T,C)\n",
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" x = self.blocks(x) # (B,T,C)\n",
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" x = self.ln_f(x) # (B,T,C)\n",
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" logits = self.lm_head(x) # (B,T,vocab_size)\n",
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"\n",
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" if targets is None:\n",
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" loss = None\n",
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" else:\n",
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" B, T, C = logits.shape\n",
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" logits = logits.view(B*T, C)\n",
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" targets = targets.view(B*T)\n",
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" loss = F.cross_entropy(logits, targets)\n",
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"\n",
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" return logits, loss\n",
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"\n",
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" def generate(self, idx, max_new_tokens):\n",
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" # idx is (B, T) array of indices in the current context\n",
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" for _ in range(max_new_tokens):\n",
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" # crop idx to the last block_size tokens\n",
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" idx_cond = idx[:, -block_size:]\n",
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" # get the predictions\n",
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" logits, loss = self(idx_cond)\n",
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" # focus only on the last time step\n",
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" logits = logits[:, -1, :] # becomes (B, C)\n",
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" # apply softmax to get probabilities\n",
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" probs = F.softmax(logits, dim=-1) # (B, C)\n",
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" # sample from the distribution\n",
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" idx_next = torch.multinomial(probs, num_samples=1) # (B, 1)\n",
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" # append sampled index to the running sequence\n",
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" idx = torch.cat((idx, idx_next), dim=1) # (B, T+1)\n",
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" return idx\n",
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"\n",
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"model = GPTLanguageModel()\n",
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"m = model.to(device)\n",
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"# print the number of parameters in the model\n",
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"print(sum(p.numel() for p in m.parameters())/1e6, 'M parameters')\n",
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"\n",
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"# create a PyTorch optimizer\n",
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"optimizer = torch.optim.AdamW(model.parameters(), lr=learning_rate)\n",
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"\n",
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"for iter in range(max_iters):\n",
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"\n",
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" # every once in a while evaluate the loss on train and val sets\n",
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" if iter % eval_interval == 0 or iter == max_iters - 1:\n",
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" losses = estimate_loss()\n",
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" print(f\"step {iter}: train loss {losses['train']:.4f}, val loss {losses['val']:.4f}\")\n",
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"\n",
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" # sample a batch of data\n",
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" xb, yb = get_batch('train')\n",
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"\n",
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" # evaluate the loss\n",
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" logits, loss = model(xb, yb)\n",
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" optimizer.zero_grad(set_to_none=True)\n",
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" loss.backward()\n",
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" optimizer.step()\n",
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"\n",
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"# generate from the model\n",
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"context = torch.zeros((1, 1), dtype=torch.long, device=device)\n",
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"print(decode(m.generate(context, max_new_tokens=500)[0].tolist()))\n",
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"#open('more.txt', 'w').write(decode(m.generate(context, max_new_tokens=10000)[0].tolist()))"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.13.2"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}
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