From 971caa808c49d8578a3a64632c7e83992890d20f Mon Sep 17 00:00:00 2001 From: Cormac Shannon <> Date: Wed, 28 Oct 2026 18:01:29 +0000 Subject: [PATCH] Vendor nanoGPT model/train/configurator verbatim Copied unmodified from karpathy/nanoGPT @ 3adf61e154c3fe3fca428ad6bc3818b27a3b8291 (MIT licence). Later commits show every change made on top. Claude-Session: https://claude.ai/code/session_01S8KN7NuUCm8nXLmy6eDuVv --- 06-experiments/nanogpt/LICENSE | 21 ++ 06-experiments/nanogpt/configurator.py | 47 ++++ 06-experiments/nanogpt/model.py | 330 ++++++++++++++++++++++++ 06-experiments/nanogpt/train.py | 336 +++++++++++++++++++++++++ 4 files changed, 734 insertions(+) create mode 100644 06-experiments/nanogpt/LICENSE create mode 100644 06-experiments/nanogpt/configurator.py create mode 100644 06-experiments/nanogpt/model.py create mode 100644 06-experiments/nanogpt/train.py diff --git a/06-experiments/nanogpt/LICENSE b/06-experiments/nanogpt/LICENSE new file mode 100644 index 0000000..329db5e --- /dev/null +++ b/06-experiments/nanogpt/LICENSE @@ -0,0 +1,21 @@ +MIT License + +Copyright (c) 2022 Andrej Karpathy + +Permission is hereby granted, free of charge, to any person obtaining a copy +of this software and associated documentation files (the "Software"), to deal +in the Software without restriction, including without limitation the rights +to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +copies of the Software, and to permit persons to whom the Software is +furnished to do so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. diff --git a/06-experiments/nanogpt/configurator.py b/06-experiments/nanogpt/configurator.py new file mode 100644 index 0000000..a8bba95 --- /dev/null +++ b/06-experiments/nanogpt/configurator.py @@ -0,0 +1,47 @@ +""" +Poor Man's Configurator. Probably a terrible idea. Example usage: +$ python train.py config/override_file.py --batch_size=32 +this will first run config/override_file.py, then override batch_size to 32 + +The code in this file will be run as follows from e.g. train.py: +>>> exec(open('configurator.py').read()) + +So it's not a Python module, it's just shuttling this code away from train.py +The code in this script then overrides the globals() + +I know people are not going to love this, I just really dislike configuration +complexity and having to prepend config. to every single variable. If someone +comes up with a better simple Python solution I am all ears. +""" + +import sys +from ast import literal_eval + +for arg in sys.argv[1:]: + if '=' not in arg: + # assume it's the name of a config file + assert not arg.startswith('--') + config_file = arg + print(f"Overriding config with {config_file}:") + with open(config_file) as f: + print(f.read()) + exec(open(config_file).read()) + else: + # assume it's a --key=value argument + assert arg.startswith('--') + key, val = arg.split('=') + key = key[2:] + if key in globals(): + try: + # attempt to eval it it (e.g. if bool, number, or etc) + attempt = literal_eval(val) + except (SyntaxError, ValueError): + # if that goes wrong, just use the string + attempt = val + # ensure the types match ok + assert type(attempt) == type(globals()[key]) + # cross fingers + print(f"Overriding: {key} = {attempt}") + globals()[key] = attempt + else: + raise ValueError(f"Unknown config key: {key}") diff --git a/06-experiments/nanogpt/model.py b/06-experiments/nanogpt/model.py new file mode 100644 index 0000000..c698f8b --- /dev/null +++ b/06-experiments/nanogpt/model.py @@ -0,0 +1,330 @@ +""" +Full definition of a GPT Language Model, all of it in this single file. +References: +1) the official GPT-2 TensorFlow implementation released by OpenAI: +https://github.com/openai/gpt-2/blob/master/src/model.py +2) huggingface/transformers PyTorch implementation: +https://github.com/huggingface/transformers/blob/main/src/transformers/models/gpt2/modeling_gpt2.py +""" + +import math +import inspect +from dataclasses import dataclass + +import torch +import torch.nn as nn +from torch.nn import functional as F + +class LayerNorm(nn.Module): + """ LayerNorm but with an optional bias. PyTorch doesn't support simply bias=False """ + + def __init__(self, ndim, bias): + super().__init__() + self.weight = nn.Parameter(torch.ones(ndim)) + self.bias = nn.Parameter(torch.zeros(ndim)) if bias else None + + def forward(self, input): + return F.layer_norm(input, self.weight.shape, self.weight, self.bias, 1e-5) + +class CausalSelfAttention(nn.Module): + + def __init__(self, config): + super().__init__() + assert config.n_embd % config.n_head == 0 + # key, query, value projections for all heads, but in a batch + self.c_attn = nn.Linear(config.n_embd, 3 * config.n_embd, bias=config.bias) + # output projection + self.c_proj = nn.Linear(config.n_embd, config.n_embd, bias=config.bias) + # regularization + self.attn_dropout = nn.Dropout(config.dropout) + self.resid_dropout = nn.Dropout(config.dropout) + self.n_head = config.n_head + self.n_embd = config.n_embd + self.dropout = config.dropout + # flash attention make GPU go brrrrr but support is only in PyTorch >= 2.0 + self.flash = hasattr(torch.nn.functional, 'scaled_dot_product_attention') + if not self.flash: + print("WARNING: using slow attention. Flash Attention requires PyTorch >= 2.0") + # causal mask to ensure that attention is only applied to the left in the input sequence + self.register_buffer("bias", torch.tril(torch.ones(config.block_size, config.block_size)) + .view(1, 1, config.block_size, config.block_size)) + + def forward(self, x): + B, T, C = x.size() # batch size, sequence length, embedding dimensionality (n_embd) + + # calculate query, key, values for all heads in batch and move head forward to be the batch dim + q, k, v = self.c_attn(x).split(self.n_embd, dim=2) + k = k.view(B, T, self.n_head, C // self.n_head).transpose(1, 2) # (B, nh, T, hs) + q = q.view(B, T, self.n_head, C // self.n_head).transpose(1, 2) # (B, nh, T, hs) + v = v.view(B, T, self.n_head, C // self.n_head).transpose(1, 2) # (B, nh, T, hs) + + # causal self-attention; Self-attend: (B, nh, T, hs) x (B, nh, hs, T) -> (B, nh, T, T) + if self.flash: + # efficient attention using Flash Attention CUDA kernels + y = torch.nn.functional.scaled_dot_product_attention(q, k, v, attn_mask=None, dropout_p=self.dropout if self.training else 0, is_causal=True) + else: + # manual implementation of attention + att = (q @ k.transpose(-2, -1)) * (1.0 / math.sqrt(k.size(-1))) + att = att.masked_fill(self.bias[:,:,:T,:T] == 0, float('-inf')) + att = F.softmax(att, dim=-1) + att = self.attn_dropout(att) + y = att @ v # (B, nh, T, T) x (B, nh, T, hs) -> (B, nh, T, hs) + y = y.transpose(1, 2).contiguous().view(B, T, C) # re-assemble all head outputs side by side + + # output projection + y = self.resid_dropout(self.c_proj(y)) + return y + +class MLP(nn.Module): + + def __init__(self, config): + super().__init__() + self.c_fc = nn.Linear(config.n_embd, 4 * config.n_embd, bias=config.bias) + self.gelu = nn.GELU() + self.c_proj = nn.Linear(4 * config.n_embd, config.n_embd, bias=config.bias) + self.dropout = nn.Dropout(config.dropout) + + def forward(self, x): + x = self.c_fc(x) + x = self.gelu(x) + x = self.c_proj(x) + x = self.dropout(x) + return x + +class Block(nn.Module): + + def __init__(self, config): + super().__init__() + self.ln_1 = LayerNorm(config.n_embd, bias=config.bias) + self.attn = CausalSelfAttention(config) + self.ln_2 = LayerNorm(config.n_embd, bias=config.bias) + self.mlp = MLP(config) + + def forward(self, x): + x = x + self.attn(self.ln_1(x)) + x = x + self.mlp(self.ln_2(x)) + return x + +@dataclass +class GPTConfig: + block_size: int = 1024 + vocab_size: int = 50304 # GPT-2 vocab_size of 50257, padded up to nearest multiple of 64 for efficiency + n_layer: int = 12 + n_head: int = 12 + n_embd: int = 768 + dropout: float = 0.0 + bias: bool = True # True: bias in Linears and LayerNorms, like GPT-2. False: a bit better and faster + +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) + # with weight tying when using torch.compile() some warnings get generated: + # "UserWarning: functional_call was passed multiple values for tied weights. + # This behavior is deprecated and will be an error in future versions" + # not 100% sure what this is, so far seems to be harmless. TODO investigate + self.transformer.wte.weight = self.lm_head.weight # https://paperswithcode.com/method/weight-tying + + # init all weights + self.apply(self._init_weights) + # apply special scaled init to the residual projections, per GPT-2 paper + 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)) + + # report number of parameters + print("number of parameters: %.2fM" % (self.get_num_params()/1e6,)) + + 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) # shape (t) + + # forward the GPT model itself + tok_emb = self.transformer.wte(idx) # token embeddings of shape (b, t, n_embd) + pos_emb = self.transformer.wpe(pos) # position embeddings of shape (t, n_embd) + x = self.transformer.drop(tok_emb + pos_emb) + for block in self.transformer.h: + x = block(x) + x = self.transformer.ln_f(x) + + if targets is not None: + # if we are given some desired targets also calculate the loss + logits = self.lm_head(x) + loss = F.cross_entropy(logits.view(-1, logits.size(-1)), targets.view(-1), ignore_index=-1) + else: + # inference-time mini-optimization: only forward the lm_head on the very last position + logits = self.lm_head(x[:, [-1], :]) # note: using list [-1] to preserve the time dim + loss = None + + return logits, loss + + def crop_block_size(self, block_size): + # model surgery to decrease the block size if necessary + # e.g. we may load the GPT2 pretrained model checkpoint (block size 1024) + # but want to use a smaller block size for some smaller, simpler model + 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 {} # default to empty dict + # only dropout can be overridden see more notes below + assert all(k == 'dropout' for k in override_args) + from transformers import GPT2LMHeadModel + print("loading weights from pretrained gpt: %s" % model_type) + + # n_layer, n_head and n_embd are determined from model_type + config_args = { + 'gpt2': dict(n_layer=12, n_head=12, n_embd=768), # 124M params + 'gpt2-medium': dict(n_layer=24, n_head=16, n_embd=1024), # 350M params + 'gpt2-large': dict(n_layer=36, n_head=20, n_embd=1280), # 774M params + 'gpt2-xl': dict(n_layer=48, n_head=25, n_embd=1600), # 1558M params + }[model_type] + print("forcing vocab_size=50257, block_size=1024, bias=True") + config_args['vocab_size'] = 50257 # always 50257 for GPT model checkpoints + config_args['block_size'] = 1024 # always 1024 for GPT model checkpoints + config_args['bias'] = True # always True for GPT model checkpoints + # we can override the dropout rate, if desired + if 'dropout' in override_args: + print(f"overriding dropout rate to {override_args['dropout']}") + config_args['dropout'] = override_args['dropout'] + # create a from-scratch initialized minGPT model + 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')] # discard this mask / buffer, not a param + + # init a huggingface/transformers model + model_hf = GPT2LMHeadModel.from_pretrained(model_type) + sd_hf = model_hf.state_dict() + + # copy while ensuring all of the parameters are aligned and match in names and shapes + sd_keys_hf = sd_hf.keys() + sd_keys_hf = [k for k in sd_keys_hf if not k.endswith('.attn.masked_bias')] # ignore these, just a buffer + sd_keys_hf = [k for k in sd_keys_hf if not k.endswith('.attn.bias')] # same, just the mask (buffer) + transposed = ['attn.c_attn.weight', 'attn.c_proj.weight', 'mlp.c_fc.weight', 'mlp.c_proj.weight'] + # basically the openai checkpoints use a "Conv1D" module, but we only want to use a vanilla Linear + # this means that we have to transpose these weights when we import them + 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): + # special treatment for the Conv1D weights we need to transpose + assert sd_hf[k].shape[::-1] == sd[k].shape + with torch.no_grad(): + sd[k].copy_(sd_hf[k].t()) + else: + # vanilla copy over the other parameters + 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): + # start with all of the candidate parameters + param_dict = {pn: p for pn, p in self.named_parameters()} + # filter out those that do not require grad + param_dict = {pn: p for pn, p in param_dict.items() if p.requires_grad} + # create optim groups. Any parameters that is 2D will be weight decayed, otherwise no. + # i.e. all weight tensors in matmuls + embeddings decay, all biases and layernorms don't. + 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") + # Create AdamW optimizer and use the fused version if it is available + 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 """ + # first estimate the number of flops we do per iteration. + # see PaLM paper Appendix B as ref: https://arxiv.org/abs/2204.02311 + 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 + # express our flops throughput as ratio of A100 bfloat16 peak flops + flops_achieved = flops_per_iter * (1.0/dt) # per second + flops_promised = 312e12 # A100 GPU bfloat16 peak flops is 312 TFLOPS + mfu = flops_achieved / flops_promised + return mfu + + @torch.no_grad() + def generate(self, idx, max_new_tokens, temperature=1.0, top_k=None): + """ + Take a conditioning sequence of indices idx (LongTensor of shape (b,t)) and complete + the sequence max_new_tokens times, feeding the predictions back into the model each time. + Most likely you'll want to make sure to be in model.eval() mode of operation for this. + """ + for _ in range(max_new_tokens): + # if the sequence context is growing too long we must crop it at block_size + idx_cond = idx if idx.size(1) <= self.config.block_size else idx[:, -self.config.block_size:] + # forward the model to get the logits for the index in the sequence + logits, _ = self(idx_cond) + # pluck the logits at the final step and scale by desired temperature + logits = logits[:, -1, :] / temperature + # optionally crop the logits to only the top k options + if top_k is not None: + v, _ = torch.topk(logits, min(top_k, logits.size(-1))) + logits[logits < v[:, [-1]]] = -float('Inf') + # apply softmax to convert logits to (normalized) probabilities + probs = F.softmax(logits, dim=-1) + # sample from the distribution + idx_next = torch.multinomial(probs, num_samples=1) + # append sampled index to the running sequence and continue + idx = torch.cat((idx, idx_next), dim=1) + + return idx diff --git a/06-experiments/nanogpt/train.py b/06-experiments/nanogpt/train.py new file mode 100644 index 0000000..de57850 --- /dev/null +++ b/06-experiments/nanogpt/train.py @@ -0,0 +1,336 @@ +""" +This training script can be run both on a single gpu in debug mode, +and also in a larger training run with distributed data parallel (ddp). + +To run on a single GPU, example: +$ python train.py --batch_size=32 --compile=False + +To run with DDP on 4 gpus on 1 node, example: +$ torchrun --standalone --nproc_per_node=4 train.py + +To run with DDP on 4 gpus across 2 nodes, example: +- Run on the first (master) node with example IP 123.456.123.456: +$ torchrun --nproc_per_node=8 --nnodes=2 --node_rank=0 --master_addr=123.456.123.456 --master_port=1234 train.py +- Run on the worker node: +$ torchrun --nproc_per_node=8 --nnodes=2 --node_rank=1 --master_addr=123.456.123.456 --master_port=1234 train.py +(If your cluster does not have Infiniband interconnect prepend NCCL_IB_DISABLE=1) +""" + +import os +import time +import math +import pickle +from contextlib import nullcontext + +import numpy as np +import torch +from torch.nn.parallel import DistributedDataParallel as DDP +from torch.distributed import init_process_group, destroy_process_group + +from model import GPTConfig, GPT + +# ----------------------------------------------------------------------------- +# default config values designed to train a gpt2 (124M) on OpenWebText +# I/O +out_dir = 'out' +eval_interval = 2000 +log_interval = 1 +eval_iters = 200 +eval_only = False # if True, script exits right after the first eval +always_save_checkpoint = True # if True, always save a checkpoint after each eval +init_from = 'scratch' # 'scratch' or 'resume' or 'gpt2*' +# wandb logging +wandb_log = False # disabled by default +wandb_project = 'owt' +wandb_run_name = 'gpt2' # 'run' + str(time.time()) +# data +dataset = 'openwebtext' +gradient_accumulation_steps = 5 * 8 # used to simulate larger batch sizes +batch_size = 12 # if gradient_accumulation_steps > 1, this is the micro-batch size +block_size = 1024 +# model +n_layer = 12 +n_head = 12 +n_embd = 768 +dropout = 0.0 # for pretraining 0 is good, for finetuning try 0.1+ +bias = False # do we use bias inside LayerNorm and Linear layers? +# adamw optimizer +learning_rate = 6e-4 # max learning rate +max_iters = 600000 # total number of training iterations +weight_decay = 1e-1 +beta1 = 0.9 +beta2 = 0.95 +grad_clip = 1.0 # clip gradients at this value, or disable if == 0.0 +# learning rate decay settings +decay_lr = True # whether to decay the learning rate +warmup_iters = 2000 # how many steps to warm up for +lr_decay_iters = 600000 # should be ~= max_iters per Chinchilla +min_lr = 6e-5 # minimum learning rate, should be ~= learning_rate/10 per Chinchilla +# DDP settings +backend = 'nccl' # 'nccl', 'gloo', etc. +# system +device = 'cuda' # examples: 'cpu', 'cuda', 'cuda:0', 'cuda:1' etc., or try 'mps' on macbooks +dtype = 'bfloat16' if torch.cuda.is_available() and torch.cuda.is_bf16_supported() else 'float16' # 'float32', 'bfloat16', or 'float16', the latter will auto implement a GradScaler +compile = True # use PyTorch 2.0 to compile the model to be faster +# ----------------------------------------------------------------------------- +config_keys = [k for k,v in globals().items() if not k.startswith('_') and isinstance(v, (int, float, bool, str))] +exec(open('configurator.py').read()) # overrides from command line or config file +config = {k: globals()[k] for k in config_keys} # will be useful for logging +# ----------------------------------------------------------------------------- + +# various inits, derived attributes, I/O setup +ddp = int(os.environ.get('RANK', -1)) != -1 # is this a ddp run? +if ddp: + init_process_group(backend=backend) + ddp_rank = int(os.environ['RANK']) + ddp_local_rank = int(os.environ['LOCAL_RANK']) + ddp_world_size = int(os.environ['WORLD_SIZE']) + device = f'cuda:{ddp_local_rank}' + torch.cuda.set_device(device) + master_process = ddp_rank == 0 # this process will do logging, checkpointing etc. + seed_offset = ddp_rank # each process gets a different seed + # world_size number of processes will be training simultaneously, so we can scale + # down the desired gradient accumulation iterations per process proportionally + assert gradient_accumulation_steps % ddp_world_size == 0 + gradient_accumulation_steps //= ddp_world_size +else: + # if not ddp, we are running on a single gpu, and one process + master_process = True + seed_offset = 0 + ddp_world_size = 1 +tokens_per_iter = gradient_accumulation_steps * ddp_world_size * batch_size * block_size +print(f"tokens per iteration will be: {tokens_per_iter:,}") + +if master_process: + os.makedirs(out_dir, exist_ok=True) +torch.manual_seed(1337 + seed_offset) +torch.backends.cuda.matmul.allow_tf32 = True # allow tf32 on matmul +torch.backends.cudnn.allow_tf32 = True # allow tf32 on cudnn +device_type = 'cuda' if 'cuda' in device else 'cpu' # for later use in torch.autocast +# note: float16 data type will automatically use a GradScaler +ptdtype = {'float32': torch.float32, 'bfloat16': torch.bfloat16, 'float16': torch.float16}[dtype] +ctx = nullcontext() if device_type == 'cpu' else torch.amp.autocast(device_type=device_type, dtype=ptdtype) + +# poor man's data loader +data_dir = os.path.join('data', dataset) +def get_batch(split): + # We recreate np.memmap every batch to avoid a memory leak, as per + # https://stackoverflow.com/questions/45132940/numpy-memmap-memory-usage-want-to-iterate-once/61472122#61472122 + if split == 'train': + data = np.memmap(os.path.join(data_dir, 'train.bin'), dtype=np.uint16, mode='r') + else: + data = np.memmap(os.path.join(data_dir, 'val.bin'), dtype=np.uint16, mode='r') + ix = torch.randint(len(data) - block_size, (batch_size,)) + x = torch.stack([torch.from_numpy((data[i:i+block_size]).astype(np.int64)) for i in ix]) + y = torch.stack([torch.from_numpy((data[i+1:i+1+block_size]).astype(np.int64)) for i in ix]) + if device_type == 'cuda': + # pin arrays x,y, which allows us to move them to GPU asynchronously (non_blocking=True) + x, y = x.pin_memory().to(device, non_blocking=True), y.pin_memory().to(device, non_blocking=True) + else: + x, y = x.to(device), y.to(device) + return x, y + +# init these up here, can override if init_from='resume' (i.e. from a checkpoint) +iter_num = 0 +best_val_loss = 1e9 + +# attempt to derive vocab_size from the dataset +meta_path = os.path.join(data_dir, 'meta.pkl') +meta_vocab_size = None +if os.path.exists(meta_path): + with open(meta_path, 'rb') as f: + meta = pickle.load(f) + meta_vocab_size = meta['vocab_size'] + print(f"found vocab_size = {meta_vocab_size} (inside {meta_path})") + +# model init +model_args = dict(n_layer=n_layer, n_head=n_head, n_embd=n_embd, block_size=block_size, + bias=bias, vocab_size=None, dropout=dropout) # start with model_args from command line +if init_from == 'scratch': + # init a new model from scratch + print("Initializing a new model from scratch") + # determine the vocab size we'll use for from-scratch training + if meta_vocab_size is None: + print("defaulting to vocab_size of GPT-2 to 50304 (50257 rounded up for efficiency)") + model_args['vocab_size'] = meta_vocab_size if meta_vocab_size is not None else 50304 + gptconf = GPTConfig(**model_args) + model = GPT(gptconf) +elif init_from == 'resume': + print(f"Resuming training from {out_dir}") + # resume training from a checkpoint. + ckpt_path = os.path.join(out_dir, 'ckpt.pt') + checkpoint = torch.load(ckpt_path, map_location=device) + checkpoint_model_args = checkpoint['model_args'] + # force these config attributes to be equal otherwise we can't even resume training + # the rest of the attributes (e.g. dropout) can stay as desired from command line + for k in ['n_layer', 'n_head', 'n_embd', 'block_size', 'bias', 'vocab_size']: + model_args[k] = checkpoint_model_args[k] + # create the model + gptconf = GPTConfig(**model_args) + model = GPT(gptconf) + state_dict = checkpoint['model'] + # fix the keys of the state dictionary :( + # honestly no idea how checkpoints sometimes get this prefix, have to debug more + unwanted_prefix = '_orig_mod.' + for k,v in list(state_dict.items()): + if k.startswith(unwanted_prefix): + state_dict[k[len(unwanted_prefix):]] = state_dict.pop(k) + model.load_state_dict(state_dict) + iter_num = checkpoint['iter_num'] + best_val_loss = checkpoint['best_val_loss'] +elif init_from.startswith('gpt2'): + print(f"Initializing from OpenAI GPT-2 weights: {init_from}") + # initialize from OpenAI GPT-2 weights + override_args = dict(dropout=dropout) + model = GPT.from_pretrained(init_from, override_args) + # read off the created config params, so we can store them into checkpoint correctly + for k in ['n_layer', 'n_head', 'n_embd', 'block_size', 'bias', 'vocab_size']: + model_args[k] = getattr(model.config, k) +# crop down the model block size if desired, using model surgery +if block_size < model.config.block_size: + model.crop_block_size(block_size) + model_args['block_size'] = block_size # so that the checkpoint will have the right value +model.to(device) + +# initialize a GradScaler. If enabled=False scaler is a no-op +scaler = torch.cuda.amp.GradScaler(enabled=(dtype == 'float16')) + +# optimizer +optimizer = model.configure_optimizers(weight_decay, learning_rate, (beta1, beta2), device_type) +if init_from == 'resume': + optimizer.load_state_dict(checkpoint['optimizer']) +checkpoint = None # free up memory + +# compile the model +if compile: + print("compiling the model... (takes a ~minute)") + unoptimized_model = model + model = torch.compile(model) # requires PyTorch 2.0 + +# wrap model into DDP container +if ddp: + model = DDP(model, device_ids=[ddp_local_rank]) + +# helps estimate an arbitrarily accurate loss over either split using many batches +@torch.no_grad() +def estimate_loss(): + out = {} + model.eval() + for split in ['train', 'val']: + losses = torch.zeros(eval_iters) + for k in range(eval_iters): + X, Y = get_batch(split) + with ctx: + logits, loss = model(X, Y) + losses[k] = loss.item() + out[split] = losses.mean() + model.train() + return out + +# learning rate decay scheduler (cosine with warmup) +def get_lr(it): + # 1) linear warmup for warmup_iters steps + if it < warmup_iters: + return learning_rate * (it + 1) / (warmup_iters + 1) + # 2) if it > lr_decay_iters, return min learning rate + if it > lr_decay_iters: + return min_lr + # 3) in between, use cosine decay down to min learning rate + decay_ratio = (it - warmup_iters) / (lr_decay_iters - warmup_iters) + assert 0 <= decay_ratio <= 1 + coeff = 0.5 * (1.0 + math.cos(math.pi * decay_ratio)) # coeff ranges 0..1 + return min_lr + coeff * (learning_rate - min_lr) + +# logging +if wandb_log and master_process: + import wandb + wandb.init(project=wandb_project, name=wandb_run_name, config=config) + +# training loop +X, Y = get_batch('train') # fetch the very first batch +t0 = time.time() +local_iter_num = 0 # number of iterations in the lifetime of this process +raw_model = model.module if ddp else model # unwrap DDP container if needed +running_mfu = -1.0 +while True: + + # determine and set the learning rate for this iteration + lr = get_lr(iter_num) if decay_lr else learning_rate + for param_group in optimizer.param_groups: + param_group['lr'] = lr + + # evaluate the loss on train/val sets and write checkpoints + if iter_num % eval_interval == 0 and master_process: + losses = estimate_loss() + print(f"step {iter_num}: train loss {losses['train']:.4f}, val loss {losses['val']:.4f}") + if wandb_log: + wandb.log({ + "iter": iter_num, + "train/loss": losses['train'], + "val/loss": losses['val'], + "lr": lr, + "mfu": running_mfu*100, # convert to percentage + }) + if losses['val'] < best_val_loss or always_save_checkpoint: + best_val_loss = losses['val'] + if iter_num > 0: + checkpoint = { + 'model': raw_model.state_dict(), + 'optimizer': optimizer.state_dict(), + 'model_args': model_args, + 'iter_num': iter_num, + 'best_val_loss': best_val_loss, + 'config': config, + } + print(f"saving checkpoint to {out_dir}") + torch.save(checkpoint, os.path.join(out_dir, 'ckpt.pt')) + if iter_num == 0 and eval_only: + break + + # forward backward update, with optional gradient accumulation to simulate larger batch size + # and using the GradScaler if data type is float16 + for micro_step in range(gradient_accumulation_steps): + if ddp: + # in DDP training we only need to sync gradients at the last micro step. + # the official way to do this is with model.no_sync() context manager, but + # I really dislike that this bloats the code and forces us to repeat code + # looking at the source of that context manager, it just toggles this variable + model.require_backward_grad_sync = (micro_step == gradient_accumulation_steps - 1) + with ctx: + logits, loss = model(X, Y) + loss = loss / gradient_accumulation_steps # scale the loss to account for gradient accumulation + # immediately async prefetch next batch while model is doing the forward pass on the GPU + X, Y = get_batch('train') + # backward pass, with gradient scaling if training in fp16 + scaler.scale(loss).backward() + # clip the gradient + if grad_clip != 0.0: + scaler.unscale_(optimizer) + torch.nn.utils.clip_grad_norm_(model.parameters(), grad_clip) + # step the optimizer and scaler if training in fp16 + scaler.step(optimizer) + scaler.update() + # flush the gradients as soon as we can, no need for this memory anymore + optimizer.zero_grad(set_to_none=True) + + # timing and logging + t1 = time.time() + dt = t1 - t0 + t0 = t1 + if iter_num % log_interval == 0 and master_process: + # get loss as float. note: this is a CPU-GPU sync point + # scale up to undo the division above, approximating the true total loss (exact would have been a sum) + lossf = loss.item() * gradient_accumulation_steps + if local_iter_num >= 5: # let the training loop settle a bit + mfu = raw_model.estimate_mfu(batch_size * gradient_accumulation_steps, dt) + running_mfu = mfu if running_mfu == -1.0 else 0.9*running_mfu + 0.1*mfu + print(f"iter {iter_num}: loss {lossf:.4f}, time {dt*1000:.2f}ms, mfu {running_mfu*100:.2f}%") + iter_num += 1 + local_iter_num += 1 + + # termination conditions + if iter_num > max_iters: + break + +if ddp: + destroy_process_group()