changes

helper.py

@@ -212,8 +212,9 @@ def generate_and_print_sample(model, tokenizer, device, start_context):
     with torch.no_grad():
         token_ids = generate(model=model, idx=encoded, max_new_tokens=100, context_size=context_size)
         decoded_text = token_ids_to_text(token_ids, tokenizer)
-        print(decoded_text.replace("\n", " "))
+        # print(decoded_text.replace("\n", " "))
     model.train()
+    return decoded_text
 
 def assign(left, right):
     if left.shape != right.shape:

helper_simple.py

@@ -0,0 +1,155 @@
+import torch
+import torch.nn as nn
+
+class MultiHeadAttn(nn.Module):
+    def __init__(self, d_in, d_out, ctx_len, dropout, num_heads, qkv_bias=False):
+        super().__init__()
+        assert d_out % num_heads == 0, "d_out must be divisible by num_heads"
+        self.d_out = d_out
+        self.num_heads = num_heads
+        self.head_dim = d_out // num_heads
+        self.W_query = nn.Linear(d_in, d_out, bias=qkv_bias)
+        self.W_key = nn.Linear(d_in, d_out, bias=qkv_bias)
+        self.W_value = nn.Linear(d_in, d_out, bias=qkv_bias)
+        self.out_proj = nn.Linear(d_out, d_out)
+        self.dropout = nn.Dropout(dropout)
+        self.register_buffer('mask', torch.triu(torch.ones(ctx_len, ctx_len), diagonal=1))
+
+    def forward(self, x):
+        b, num_tokens, d_in = x.shape
+        keys = self.W_key(x).view(b, num_tokens, self.num_heads, self.head_dim).transpose(1, 2)
+        queries = self.W_query(x).view(b, num_tokens, self.num_heads, self.head_dim).transpose(1, 2)
+        values = self.W_value(x).view(b, num_tokens, self.num_heads, self.head_dim).transpose(1, 2)
+        attn_scores = queries @ keys.transpose(2, 3)
+        mask_bool = self.mask.bool()[:num_tokens, :num_tokens]
+        attn_scores.masked_fill_(mask_bool, -torch.inf)
+        attn_weights = torch.softmax(attn_scores / keys.shape[-1]**0.5, dim=-1)
+        attn_weights = self.dropout(attn_weights)
+        context_vec = (attn_weights @ values).transpose(1, 2).reshape(b, num_tokens, self.d_out)
+        return self.out_proj(context_vec)
+
+class FeedForward(nn.Module):
+    def __init__(self, cfg):
+        super().__init__()
+        self.layers = nn.Sequential(
+            nn.Linear(cfg["emb_dim"], 4 * cfg["emb_dim"]),
+            GELU(),
+            nn.Linear(4 * cfg["emb_dim"], cfg["emb_dim"]),
+        )
+
+    def forward(self, x):
+        return self.layers(x)
+
+class GELU(nn.Module):
+    def forward(self, x):
+        return 0.5 * x * (1 + torch.tanh(
+            torch.sqrt(torch.tensor(2.0 / torch.pi)) * (x + 0.044715 * x**3)
+        ))
+
+class LayerNorm(nn.Module):
+    def __init__(self, emb_dim):
+        super().__init__()
+        self.eps = 1e-5
+        self.scale = nn.Parameter(torch.ones(emb_dim))
+        self.shift = nn.Parameter(torch.zeros(emb_dim))
+
+    def forward(self, x):
+        mean = x.mean(dim=-1, keepdim=True)
+        var = x.var(dim=-1, keepdim=True, unbiased=False)
+        norm_x = (x - mean) / torch.sqrt(var + self.eps)
+        return self.scale * norm_x + self.shift
+
+class TransformerBlock(nn.Module):
+    def __init__(self, cfg):
+        super().__init__()
+        self.att = MultiHeadAttn(
+            d_in=cfg["emb_dim"],
+            d_out=cfg["emb_dim"],
+            ctx_len=cfg["context_length"],
+            num_heads=cfg["n_heads"],
+            dropout=cfg["drop_rate"],
+            qkv_bias=cfg["qkv_bias"])
+        self.ff = FeedForward(cfg)
+        self.norm1 = LayerNorm(cfg["emb_dim"])
+        self.norm2 = LayerNorm(cfg["emb_dim"])
+        self.drop_resid = nn.Dropout(cfg["drop_rate"])
+
+    def forward(self, x):
+        save = x
+        x = self.norm1(x)
+        x = self.att(x)
+        x = self.drop_resid(x)
+        x += save
+        save = x
+        x = self.norm2(x)
+        x = self.ff(x)
+        x = self.drop_resid(x)
+        x += save
+        return x
+
+class GPT(nn.Module):
+    def __init__(self, cfg):
+        super().__init__()
+        self.tok_emb = nn.Embedding(cfg["vocab_size"], cfg["emb_dim"])
+        self.pos_emb = nn.Embedding(cfg["context_length"], cfg["emb_dim"])
+        self.drop_emb = nn.Dropout(cfg["drop_rate"])
+        self.trf_blocks = nn.Sequential(
+            *[TransformerBlock(cfg) for _ in range(cfg["n_layers"])]
+        )
+        self.final_norm = LayerNorm(cfg["emb_dim"])
+        self.out_head = nn.Linear(cfg["emb_dim"], cfg["vocab_size"], bias=False)
+
+    def forward(self, in_idx):
+        batch_size, seq_len = in_idx.shape
+        tok_embeds = self.tok_emb(in_idx)
+        pos_embeds = self.pos_emb(torch.arange(seq_len, device=in_idx.device))
+        x = tok_embeds + pos_embeds
+        x = self.drop_emb(x)
+        x = self.trf_blocks(x)
+        x = self.final_norm(x)
+        return self.out_head(x)
+
+def generate(model, idx, max_new_tokens, context_size, temperature=0.0, top_k=None, eos_id=None):
+    for _ in range(max_new_tokens):
+        idx_cond = idx[:, -context_size:]
+        with torch.no_grad():
+            logits = model(idx_cond)
+        logits = logits[:, -1, :]
+
+        if top_k is not None:
+            top_logits, _ = torch.topk(logits, top_k)
+            min_val = top_logits[:, -1]
+            logits = torch.where(logits < min_val, torch.tensor(float('-inf')).to(logits.device), logits)
+
+        if temperature > 0.0:
+            logits = logits / temperature
+            probs = torch.softmax(logits, dim=-1)
+            idx_next = torch.multinomial(probs, num_samples=1)
+        else:
+            idx_next = torch.argmax(logits, dim=-1, keepdim=True)
+
+        if eos_id is not None and idx_next == eos_id:
+            break
+
+        idx = torch.cat((idx, idx_next), dim=1)
+
+    return idx
+
+def generate_and_print_sample(model, tokenizer, device, start_context):
+    model.eval()
+    context_size = model.pos_emb.weight.shape[0]
+    encoded = text_to_token_ids(start_context, tokenizer).to(device)
+    with torch.no_grad():
+        token_ids = generate(model=model, idx=encoded, max_new_tokens=100, context_size=context_size)
+        decoded_text = token_ids_to_text(token_ids, tokenizer)
+    model.train()
+    return decoded_text
+
+def text_to_token_ids(text, tokenizer):
+    encoded = tokenizer.encode(text, allowed_special={"<|endoftext|>"})
+    encoded_tensor = torch.tensor(encoded).unsqueeze(0)
+    return encoded_tensor
+
+def token_ids_to_text(token_ids, tokenizer):
+    flat = token_ids.squeeze(0)
+    return tokenizer.decode(flat.tolist())