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| class GPT(nn.Module): def __init__(self, config): super().__init__() assert config.vocab_size is not None assert config.block_size is not None self.config = config self.transformer = nn.ModuleDict(dict( wte = nn.Embedding(config.vocab_size, config.n_embd), wpe = nn.Embedding(config.block_size, config.n_embd), drop = nn.Dropout(config.dropout), h = nn.ModuleList([Block(config) for _ in range(config.n_layer)]), ln_f = LayerNorm(config.n_embd, bias=config.bias), )) self.lm_head = nn.Linear(config.n_embd, config.vocab_size, bias=False) self.transformer.wte.weight = self.lm_head.weight
self.apply(self._init_weights) for pn, p in self.named_parameters(): if pn.endswith('c_proj.weight'): torch.nn.init.normal_(p, mean=0.0, std=0.02/math.sqrt(2 * config.n_layer))
print("number of parameters: %.2fM" % (self.get_num_params()/1e6,))
self.dictionary = {}
def get_num_params(self, non_embedding=True): """ Return the number of parameters in the model. For non-embedding count (default), the position embeddings get subtracted. The token embeddings would too, except due to the parameter sharing these params are actually used as weights in the final layer, so we include them. """ n_params = sum(p.numel() for p in self.parameters()) if non_embedding: n_params -= self.transformer.wpe.weight.numel() return n_params
def _init_weights(self, module): if isinstance(module, nn.Linear): torch.nn.init.normal_(module.weight, mean=0.0, std=0.02) if module.bias is not None: torch.nn.init.zeros_(module.bias) elif isinstance(module, nn.Embedding): torch.nn.init.normal_(module.weight, mean=0.0, std=0.02)
def forward(self, idx, targets=None): device = idx.device b, t = idx.size() assert t <= self.config.block_size, f"Cannot forward sequence of length {t}, block size is only {self.config.block_size}" pos = torch.arange(0, t, dtype=torch.long, device=device)
tok_emb = self.transformer.wte(idx) pos_emb = self.transformer.wpe(pos) input_emb = tok_emb + pos_emb input_emb_dropout = self.transformer.drop(input_emb) self.dictionary["block"] = {}
x = input_emb_dropout for i, block in enumerate(self.transformer.h): x = block(x) if (i == 0): self.dictionary["block"][f"block_{i}"] = block.dict x = self.transformer.ln_f(x) if targets is not None: logits = self.lm_head(x) loss = F.cross_entropy(logits.view(-1, logits.size(-1)), targets.view(-1), ignore_index=-1) else: logits = self.lm_head(x[:, [-1], :]) loss = None
self.dictionary["linear"] = { "output": logits }
return self.dictionary
def crop_block_size(self, block_size): assert block_size <= self.config.block_size self.config.block_size = block_size self.transformer.wpe.weight = nn.Parameter(self.transformer.wpe.weight[:block_size]) for block in self.transformer.h: if hasattr(block.attn, 'bias'): block.attn.bias = block.attn.bias[:,:,:block_size,:block_size]
@classmethod def from_pretrained(cls, model_type, override_args=None): assert model_type in {'gpt2', 'gpt2-medium', 'gpt2-large', 'gpt2-xl'} override_args = override_args or {} assert all(k == 'dropout' for k in override_args) from transformers import GPT2LMHeadModel print("loading weights from pretrained gpt: %s" % model_type)
config_args = { 'gpt2': dict(n_layer=12, n_head=12, n_embd=768), 'gpt2-medium': dict(n_layer=24, n_head=16, n_embd=1024), 'gpt2-large': dict(n_layer=36, n_head=20, n_embd=1280), 'gpt2-xl': dict(n_layer=48, n_head=25, n_embd=1600), }[model_type] print("forcing vocab_size=50257, block_size=1024, bias=True") config_args['vocab_size'] = 50257 config_args['block_size'] = 1024 config_args['bias'] = True if 'dropout' in override_args: print(f"overriding dropout rate to {override_args['dropout']}") config_args['dropout'] = override_args['dropout'] config = GPTConfig(**config_args) model = GPT(config) sd = model.state_dict() sd_keys = sd.keys() sd_keys = [k for k in sd_keys if not k.endswith('.attn.bias')]
model_hf = GPT2LMHeadModel.from_pretrained(model_type) sd_hf = model_hf.state_dict()
sd_keys_hf = sd_hf.keys() sd_keys_hf = [k for k in sd_keys_hf if not k.endswith('.attn.masked_bias')] sd_keys_hf = [k for k in sd_keys_hf if not k.endswith('.attn.bias')] transposed = ['attn.c_attn.weight', 'attn.c_proj.weight', 'mlp.c_fc.weight', 'mlp.c_proj.weight'] assert len(sd_keys_hf) == len(sd_keys), f"mismatched keys: {len(sd_keys_hf)} != {len(sd_keys)}" for k in sd_keys_hf: if any(k.endswith(w) for w in transposed): assert sd_hf[k].shape[::-1] == sd[k].shape with torch.no_grad(): sd[k].copy_(sd_hf[k].t()) else: assert sd_hf[k].shape == sd[k].shape with torch.no_grad(): sd[k].copy_(sd_hf[k])
return model
def configure_optimizers(self, weight_decay, learning_rate, betas, device_type): param_dict = {pn: p for pn, p in self.named_parameters()} param_dict = {pn: p for pn, p in param_dict.items() if p.requires_grad} decay_params = [p for n, p in param_dict.items() if p.dim() >= 2] nodecay_params = [p for n, p in param_dict.items() if p.dim() < 2] optim_groups = [ {'params': decay_params, 'weight_decay': weight_decay}, {'params': nodecay_params, 'weight_decay': 0.0} ] num_decay_params = sum(p.numel() for p in decay_params) num_nodecay_params = sum(p.numel() for p in nodecay_params) print(f"num decayed parameter tensors: {len(decay_params)}, with {num_decay_params:,} parameters") print(f"num non-decayed parameter tensors: {len(nodecay_params)}, with {num_nodecay_params:,} parameters") fused_available = 'fused' in inspect.signature(torch.optim.AdamW).parameters use_fused = fused_available and device_type == 'cuda' extra_args = dict(fused=True) if use_fused else dict() optimizer = torch.optim.AdamW(optim_groups, lr=learning_rate, betas=betas, **extra_args) print(f"using fused AdamW: {use_fused}")
return optimizer
def estimate_mfu(self, fwdbwd_per_iter, dt): """ estimate model flops utilization (MFU) in units of A100 bfloat16 peak FLOPS """ N = self.get_num_params() cfg = self.config L, H, Q, T = cfg.n_layer, cfg.n_head, cfg.n_embd//cfg.n_head, cfg.block_size flops_per_token = 6*N + 12*L*H*Q*T flops_per_fwdbwd = flops_per_token * T flops_per_iter = flops_per_fwdbwd * fwdbwd_per_iter flops_achieved = flops_per_iter * (1.0/dt) flops_promised = 312e12 mfu = flops_achieved / flops_promised return mfu
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