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train_pt.py
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train_pt.py
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"""
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 in debug mode example:
$ python train.py --batch_size=32 --other=args
To run DDP on 4 gpus on one node, example:
$ torchrun --standalone --nproc_per_node=4 train.py
"""
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'
batch_size = 12
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+
# adamw optimizer
learning_rate = 6e-4 # max learning rate
max_iters = 600000 # total number of training iterations
weight_decay = 1e-2
beta1 = 0.9
beta2 = 0.95
# 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.
dtype = 'bfloat16' # 'float32' or 'bfloat16'
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('LOCAL_RANK', -1)) != -1 # is this a ddp run?
if ddp:
init_process_group(backend=backend)
gpu_id = int(os.environ["LOCAL_RANK"])
device = f"cuda:{gpu_id}"
else:
gpu_id = 0 # gpu_id 0 means this is the (single) master process, basically
if gpu_id == 0:
os.makedirs(out_dir, exist_ok=True)
torch.manual_seed(1337 + gpu_id) # note: each worker gets a different seed
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 would require us to change the code to use a GradScaler
ptdtype = {'float32': torch.float32, 'bfloat16': torch.bfloat16}[dtype]
ctx = nullcontext() if device_type == 'cpu' else torch.amp.autocast(device_type=device_type, dtype=ptdtype)
# poor man's data loader, TODO evaluate need for actual DataLoader
data_dir = os.path.join('data', dataset)
train_data = np.memmap(os.path.join(data_dir, 'train.bin'), dtype=np.uint16, mode='r')
val_data = np.memmap(os.path.join(data_dir, 'val.bin'), dtype=np.uint16, mode='r')
def get_batch(split):
data = train_data if split == 'train' else val_data
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])
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')
if os.path.exists(meta_path):
with open(meta_path, 'rb') as f:
meta = pickle.load(f)
vocab_size = meta['vocab_size']
print(f"vocab_size = {vocab_size} (from {meta_path})")
else:
print(f"vocab_size not found in {meta_path}, using GPT-2 default of 50257")
vocab_size = 50257
# model init
model_args = dict(n_layer = n_layer, n_head = n_head, n_embd = n_embd, block_size = block_size, dropout = dropout, vocab_size = vocab_size)
if init_from == 'scratch':
# init a new model from scratch
print("Initializing a new model from scratch")
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']
for k, v in model_args.items():
assert checkpoint_model_args[k] == v, "for now"
# TODO: think through how passed in params should interact with checkpoint params
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 and override the GPT sizing model args from the model config
model_args['n_layer'] = model.config.n_layer
model_args['n_head'] = model.config.n_head
model_args['n_embd'] = model.config.n_embd
# crop down the model block size if desired
if block_size < model.config.block_size:
model.crop_block_size(block_size)
model.to(device)
# optimizer
optimizer = model.configure_optimizers(weight_decay, learning_rate, (beta1, beta2))
if init_from == 'resume':
optimizer.load_state_dict(checkpoint['optimizer'])
# 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=[gpu_id])
@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(iter):
# 1) linear warmup for warmup_iters steps
if iter < warmup_iters:
return learning_rate * iter / warmup_iters
# 2) if iter > lr_decay_iters, return min learning rate
if iter > lr_decay_iters:
return min_lr
# 3) in between, use cosine decay down to min learning rate
decay_ratio = (iter - 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 gpu_id == 0:
import wandb
wandb.init(project=wandb_project, name=wandb_run_name, config=config)
# training loop
t0 = time.time()
while True:
# determine the learning rate for this iteration
if decay_lr:
lr = get_lr(iter_num)
for param_group in optimizer.param_groups:
param_group['lr'] = lr
else:
lr = learning_rate
if iter_num % eval_interval == 0 and gpu_id == 0:
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,
})
if losses['val'] < best_val_loss or always_save_checkpoint:
best_val_loss = losses['val']
raw_model = model.module if ddp else model
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
X, Y = get_batch('train')
with ctx:
logits, loss = model(X, Y)
optimizer.zero_grad(set_to_none=True)
loss.backward()
# TODO: gradient clipping evaluate need for
optimizer.step()
t1 = time.time()
dt = t1 - t0
t0 = t1
if iter_num % log_interval == 0 and gpu_id == 0:
lossf = loss.item() # loss as float. TODO CPU-GPU sync: profile, make sure not slow af
print(f"iter {iter_num}: loss {lossf:.4f}, time {dt*1000:.2f}ms")
iter_num += 1
# termination conditions
if iter_num > max_iters:
break
if ddp:
destroy_process_group()