# Ultralytics YOLO 🚀, AGPL-3.0 license
"""
Train a model on a dataset
Usage:
$ yolo mode=train model=yolov8n.pt data=coco128.yaml imgsz=640 epochs=100 batch=16
"""
import os
import subprocess
import time
from copy import deepcopy
from datetime import datetime, timedelta
from pathlib import Path
import numpy as np
import torch
import torch.distributed as dist
import torch.nn as nn
from torch.cuda import amp
from torch.nn.parallel import DistributedDataParallel as DDP
from torch.optim import lr_scheduler
from tqdm import tqdm
from ultralytics.nn.tasks import attempt_load_one_weight, attempt_load_weights
from ultralytics.yolo.cfg import get_cfg
from ultralytics.yolo.data.utils import check_cls_dataset, check_det_dataset
from ultralytics.yolo.utils import (DEFAULT_CFG, LOGGER, ONLINE, RANK, ROOT, SETTINGS, TQDM_BAR_FORMAT, __version__,
callbacks, clean_url, colorstr, emojis, yaml_save)
from ultralytics.yolo.utils.autobatch import check_train_batch_size
from ultralytics.yolo.utils.checks import check_file, check_imgsz, print_args
from ultralytics.yolo.utils.dist import ddp_cleanup, generate_ddp_command
from ultralytics.yolo.utils.files import get_latest_run, increment_path
from ultralytics.yolo.utils.torch_utils import (EarlyStopping, ModelEMA, de_parallel, init_seeds, one_cycle,
select_device, strip_optimizer)
class BaseTrainer:
"""
BaseTrainer
A base class for creating trainers.
Attributes:
args (SimpleNamespace): Configuration for the trainer.
check_resume (method): Method to check if training should be resumed from a saved checkpoint.
validator (BaseValidator): Validator instance.
model (nn.Module): Model instance.
callbacks (defaultdict): Dictionary of callbacks.
save_dir (Path): Directory to save results.
wdir (Path): Directory to save weights.
last (Path): Path to last checkpoint.
best (Path): Path to best checkpoint.
save_period (int): Save checkpoint every x epochs (disabled if < 1).
batch_size (int): Batch size for training.
epochs (int): Number of epochs to train for.
start_epoch (int): Starting epoch for training.
device (torch.device): Device to use for training.
amp (bool): Flag to enable AMP (Automatic Mixed Precision).
scaler (amp.GradScaler): Gradient scaler for AMP.
data (str): Path to data.
trainset (torch.utils.data.Dataset): Training dataset.
testset (torch.utils.data.Dataset): Testing dataset.
ema (nn.Module): EMA (Exponential Moving Average) of the model.
lf (nn.Module): Loss function.
scheduler (torch.optim.lr_scheduler._LRScheduler): Learning rate scheduler.
best_fitness (float): The best fitness value achieved.
fitness (float): Current fitness value.
loss (float): Current loss value.
tloss (float): Total loss value.
loss_names (list): List of loss names.
csv (Path): Path to results CSV file.
"""
def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
"""
Initializes the BaseTrainer class.
Args:
cfg (str, optional): Path to a configuration file. Defaults to DEFAULT_CFG.
overrides (dict, optional): Configuration overrides. Defaults to None.
"""
self.args = get_cfg(cfg, overrides)
self.device = select_device(self.args.device, self.args.batch)
self.check_resume()
self.validator = None
self.model = None
self.metrics = None
self.plots = {}
init_seeds(self.args.seed + 1 + RANK, deterministic=self.args.deterministic)
# Dirs
project = self.args.project or Path(SETTINGS['runs_dir']) / self.args.task
name = self.args.name or f'{self.args.mode}'
if hasattr(self.args, 'save_dir'):
self.save_dir = Path(self.args.save_dir)
else:
self.save_dir = Path(
increment_path(Path(project) / name, exist_ok=self.args.exist_ok if RANK in (-1, 0) else True))
self.wdir = self.save_dir / 'weights' # weights dir
if RANK in (-1, 0):
self.wdir.mkdir(parents=True, exist_ok=True) # make dir
self.args.save_dir = str(self.save_dir)
yaml_save(self.save_dir / 'args.yaml', vars(self.args)) # save run args
self.last, self.best = self.wdir / 'last.pt', self.wdir / 'best.pt' # checkpoint paths
self.save_period = self.args.save_period
self.batch_size = self.args.batch
self.epochs = self.args.epochs
self.start_epoch = 0
if RANK == -1:
print_args(vars(self.args))
# Device
if self.device.type == 'cpu':
self.args.workers = 0 # faster CPU training as time dominated by inference, not dataloading
# Model and Dataset
self.model = self.args.model
try:
if self.args.task == 'classify':
self.data = check_cls_dataset(self.args.data)
elif self.args.data.endswith('.yaml') or self.args.task in ('detect', 'segment'):
self.data = check_det_dataset(self.args.data)
if 'yaml_file' in self.data:
self.args.data = self.data['yaml_file'] # for validating 'yolo train data=url.zip' usage
except Exception as e:
raise RuntimeError(emojis(f"Dataset '{clean_url(self.args.data)}' error ❌ {e}")) from e
self.trainset, self.testset = self.get_dataset(self.data)
self.ema = None
# Optimization utils init
self.lf = None
self.scheduler = None
# Epoch level metrics
self.best_fitness = None
self.fitness = None
self.loss = None
self.tloss = None
self.loss_names = ['Loss']
self.csv = self.save_dir / 'results.csv'
self.plot_idx = [0, 1, 2]
# Callbacks
self.callbacks = _callbacks or callbacks.get_default_callbacks()
if RANK in (-1, 0):
callbacks.add_integration_callbacks(self)
def add_callback(self, event: str, callback):
"""
Appends the given callback.
"""
self.callbacks[event].append(callback)
def set_callback(self, event: str, callback):
"""
Overrides the existing callbacks with the given callback.
"""
self.callbacks[event] = [callback]
def run_callbacks(self, event: str):
"""Run all existing callbacks associated with a particular event."""
for callback in self.callbacks.get(event, []):
callback(self)
def train(self):
"""Allow device='', device=None on Multi-GPU systems to default to device=0."""
if isinstance(self.args.device, int) or self.args.device: # i.e. device=0 or device=[0,1,2,3]
world_size = torch.cuda.device_count()
elif torch.cuda.is_available(): # i.e. device=None or device=''
world_size = 1 # default to device 0
else: # i.e. device='cpu' or 'mps'
world_size = 0
# Run subprocess if DDP training, else train normally
if world_size > 1 and 'LOCAL_RANK' not in os.environ:
# Argument checks
if self.args.rect:
LOGGER.warning("WARNING ⚠️ 'rect=True' is incompatible with Multi-GPU training, setting rect=False")
self.args.rect = False
# Command
cmd, file = generate_ddp_command(world_size, self)
try:
LOGGER.info(f'Running DDP command {cmd}')
subprocess.run(cmd, check=True)
except Exception as e:
raise e
finally:
ddp_cleanup(self, str(file))
else:
self._do_train(world_size)
def _setup_ddp(self, world_size):
"""Initializes and sets the DistributedDataParallel parameters for training."""
torch.cuda.set_device(RANK)
self.device = torch.device('cuda', RANK)
LOGGER.info(f'DDP settings: RANK {RANK}, WORLD_SIZE {world_size}, DEVICE {self.device}')
os.environ['NCCL_BLOCKING_WAIT'] = '1' # set to enforce timeout
dist.init_process_group('nccl' if dist.is_nccl_available() else 'gloo',
timeout=timedelta(seconds=3600),
rank=RANK,
world_size=world_size)
def _setup_train(self, world_size):
"""
Builds dataloaders and optimizer on correct rank process.
"""
# Model
self.run_callbacks('on_pretrain_routine_start')
ckpt = self.setup_model()
self.model = self.model.to(self.device)
self.set_model_attributes()
# Check AMP
self.amp = torch.tensor(self.args.amp).to(self.device) # True or False
if self.amp and RANK in (-1, 0): # Single-GPU and DDP
callbacks_backup = callbacks.default_callbacks.copy() # backup callbacks as check_amp() resets them
self.amp = torch.tensor(check_amp(self.model), device=self.device)
callbacks.default_callbacks = callbacks_backup # restore callbacks
if RANK > -1: # DDP
dist.broadcast(self.amp, src=0) # broadcast the tensor from rank 0 to all other ranks (returns None)
self.amp = bool(self.amp) # as boolean
self.scaler = amp.GradScaler(enabled=self.amp)
if world_size > 1:
self.model = DDP(self.model, device_ids=[RANK])
# Check imgsz
gs = max(int(self.model.stride.max() if hasattr(self.model, 'stride') else 32), 32) # grid size (max stride)
self.args.imgsz = check_imgsz(self.args.imgsz, stride=gs, floor=gs, max_dim=1)
# Batch size
if self.batch_size == -1:
if RANK == -1: # single-GPU only, estimate best batch size
self.batch_size = check_train_batch_size(self.model, self.args.imgsz, self.amp)
else:
SyntaxError('batch=-1 to use AutoBatch is only available in Single-GPU training. '
'Please pass a valid batch size value for Multi-GPU DDP training, i.e. batch=16')
# Optimizer
self.accumulate = max(round(self.args.nbs / self.batch_size), 1) # accumulate loss before optimizing
weight_decay = self.args.weight_decay * self.batch_size * self.accumulate / self.args.nbs # scale weight_decay
self.optimizer = self.build_optimizer(model=self.model,
name=self.args.optimizer,
lr=self.args.lr0,
momentum=self.args.momentum,
decay=weight_decay)
# Scheduler
if self.args.cos_lr:
self.lf = one_cycle(1, self.args.lrf, self.epochs) # cosine 1->hyp['lrf']
else:
self.lf = lambda x: (1 - x / self.epochs) * (1.0 - self.args.lrf) + self.args.lrf # linear
self.scheduler = lr_scheduler.LambdaLR(self.optimizer, lr_lambda=self.lf)
self.stopper, self.stop = EarlyStopping(patience=self.args.patience), False
# Dataloaders
batch_size = self.batch_size // world_size if world_size > 1 else self.batch_size
self.train_loader = self.get_dataloader(self.trainset, batch_size=batch_size, rank=RANK, mode='train')
if RANK in (-1, 0):
self.test_loader = self.get_dataloader(self.testset, batch_size=batch_size * 2, rank=-1, mode='val')
self.validator = self.get_validator()
metric_keys = self.validator.metrics.keys + self.label_loss_items(prefix='val')
self.metrics = dict(zip(metric_keys, [0] * len(metric_keys))) # TODO: init metrics for plot_results()?
self.ema = ModelEMA(self.model)
if self.args.plots and not self.args.v5loader:
self.plot_training_labels()
self.resume_training(ckpt)
self.scheduler.last_epoch = self.start_epoch - 1 # do not move
self.run_callbacks('on_pretrain_routine_end')
def _do_train(self, world_size=1):
"""Train completed, evaluate and plot if specified by arguments."""
if world_size > 1:
self._setup_ddp(world_size)
self._setup_train(world_size)
self.epoch_time = None
self.epoch_time_start = time.time()
self.train_time_start = time.time()
nb = len(self.train_loader) # number of batches
nw = max(round(self.args.warmup_epochs * nb), 100) # number of warmup iterations
last_opt_step = -1
self.run_callbacks('on_train_start')
LOGGER.info(f'Image sizes {self.args.imgsz} train, {self.args.imgsz} val\n'
f'Using {self.train_loader.num_workers * (world_size or 1)} dataloader workers\n'
f"Logging results to {colorstr('bold', self.save_dir)}\n"
f'Starting training for {self.epochs} epochs...')
if self.args.close_mosaic:
base_idx = (self.epochs - self.args.close_mosaic) * nb
self.plot_idx.extend([base_idx, base_idx + 1, base_idx + 2])
epoch = self.epochs # predefine for resume fully trained model edge cases
for epoch in range(self.start_epoch, self.epochs):
self.epoch = epoch
self.run_callbacks('on_train_epoch_start')
self.model.train()
if RANK != -1:
self.train_loader.sampler.set_epoch(epoch)
pbar = enumerate(self.train_loader)
# Update dataloader attributes (optional)
if epoch == (self.epochs - self.args.close_mosaic):
LOGGER.info('Closing dataloader mosaic')
if hasattr(self.train_loader.dataset, 'mosaic'):
self.train_loader.dataset.mosaic = False
if hasattr(self.train_loader.dataset, 'close_mosaic'):
self.train_loader.dataset.close_mosaic(hyp=self.args)
self.train_loader.reset()
if RANK in (-1, 0):
LOGGER.info(self.progress_string())
pbar = tqdm(enumerate(self.train_loader), total=nb, bar_format=TQDM_BAR_FORMAT)
self.tloss = None
self.optimizer.zero_grad()
for i, batch in pbar:
self.run_callbacks('on_train_batch_start')
# Warmup
ni = i + nb * epoch
if ni <= nw:
xi = [0, nw] # x interp
self.accumulate = max(1, np.interp(ni, xi, [1, self.args.nbs / self.batch_size]).round())
for j, x in enumerate(self.optimizer.param_groups):
# Bias lr falls from 0.1 to lr0, all other lrs rise from 0.0 to lr0
x['lr'] = np.interp(
ni, xi, [self.args.warmup_bias_lr if j == 0 else 0.0, x['initial_lr'] * self.lf(epoch)])
if 'momentum' in x:
x['momentum'] = np.interp(ni, xi, [self.args.warmup_momentum, self.args.momentum])
# Forward
with torch.cuda.amp.autocast(self.amp):
batch = self.preprocess_batch(batch)
preds = self.model(batch['img'])
self.loss, self.loss_items = self.criterion(preds, batch)
if RANK != -1:
self.loss *= world_size
self.tloss = (self.tloss * i + self.loss_items) / (i + 1) if self.tloss is not None \
else self.loss_items
# Backward
self.scaler.scale(self.loss).backward()
# Optimize - https://pytorch.org/docs/master/notes/amp_examples.html
if ni - last_opt_step >= self.accumulate:
self.optimizer_step()
last_opt_step = ni
# Log
mem = f'{torch.cuda.memory_reserved() / 1E9 if torch.cuda.is_available() else 0:.3g}G' # (GB)
loss_len = self.tloss.shape[0] if len(self.tloss.size()) else 1
losses = self.tloss if loss_len > 1 else torch.unsqueeze(self.tloss, 0)
if RANK in (-1, 0):
pbar.set_description(
('%11s' * 2 + '%11.4g' * (2 + loss_len)) %
(f'{epoch + 1}/{self.epochs}', mem, *losses, batch['cls'].shape[0], batch['img'].shape[-1]))
self.run_callbacks('on_batch_end')
if self.args.plots and ni in self.plot_idx:
self.plot_training_samples(batch, ni)
self.run_callbacks('on_train_batch_end')
self.lr = {f'lr/pg{ir}': x['lr'] for ir, x in enumerate(self.optimizer.param_groups)} # for loggers
self.scheduler.step()
self.run_callbacks('on_train_epoch_end')
if RANK in (-1, 0):
# Validation
self.ema.update_attr(self.model, include=['yaml', 'nc', 'args', 'names', 'stride', 'class_weights'])
final_epoch = (epoch + 1 == self.epochs) or self.stopper.possible_stop
if self.args.val or final_epoch:
self.metrics, self.fitness = self.validate()
self.save_metrics(metrics={**self.label_loss_items(self.tloss), **self.metrics, **self.lr})
self.stop = self.stopper(epoch + 1, self.fitness)
# Save model
if self.args.save or (epoch + 1 == self.epochs):
self.save_model()
self.run_callbacks('on_model_save')
tnow = time.time()
self.epoch_time = tnow - self.epoch_time_start
self.epoch_time_start = tnow
self.run_callbacks('on_fit_epoch_end')
torch.cuda.empty_cache() # clears GPU vRAM at end of epoch, can help with out of memory errors
# Early Stopping
if RANK != -1: # if DDP training
broadcast_list = [self.stop if RANK == 0 else None]
dist.broadcast_object_list(broadcast_list, 0) # broadcast 'stop' to all ranks
if RANK != 0:
self.stop = broadcast_list[0]
if self.stop:
break # must break all DDP ranks
if RANK in (-1, 0):
# Do final val with best.pt
LOGGER.info(f'\n{epoch - self.start_epoch + 1} epochs completed in '
f'{(time.time() - self.train_time_start) / 3600:.3f} hours.')
self.final_eval()
if self.args.plots:
self.plot_metrics()
self.run_callbacks('on_train_end')
torch.cuda.empty_cache()
self.run_callbacks('teardown')
def save_model(self):
"""Save model checkpoints based on various conditions."""
ckpt = {
'epoch': self.epoch,
'best_fitness': self.best_fitness,
'model': deepcopy(de_parallel(self.model)).half(),
'ema': deepcopy(self.ema.ema).half(),
'updates': self.ema.updates,
'optimizer': self.optimizer.state_dict(),
'train_args': vars(self.args), # save as dict
'date': datetime.now().isoformat(),
'version': __version__}
# Use dill (if exists) to serialize the lambda functions where pickle does not do this
try:
import dill as pickle
except ImportError:
import pickle
# Save last, best and delete
torch.save(ckpt, self.last, pickle_module=pickle)
if self.best_fitness == self.fitness:
torch.save(ckpt, self.best, pickle_module=pickle)
if (self.epoch > 0) and (self.save_period > 0) and (self.epoch % self.save_period == 0):
torch.save(ckpt, self.wdir / f'epoch{self.epoch}.pt', pickle_module=pickle)
del ckpt
@staticmethod
def get_dataset(data):
"""
Get train, val path from data dict if it exists. Returns None if data format is not recognized.
"""
return data['train'], data.get('val') or data.get('test')
def setup_model(self):
"""
load/create/download model for any task.
"""
if isinstance(self.model, torch.nn.Module): # if model is loaded beforehand. No setup needed
return
model, weights = self.model, None
ckpt = None
if str(model).endswith('.pt'):
weights, ckpt = attempt_load_one_weight(model)
cfg = ckpt['model'].yaml
else:
cfg = model
self.model = self.get_model(cfg=cfg, weights=weights, verbose=RANK == -1) # calls Model(cfg, weights)
return ckpt
def optimizer_step(self):
"""Perform a single step of the training optimizer with gradient clipping and EMA update."""
self.scaler.unscale_(self.optimizer) # unscale gradients
torch.nn.utils.clip_grad_norm_(self.model.parameters(), max_norm=10.0) # clip gradients
self.scaler.step(self.optimizer)
self.scaler.update()
self.optimizer.zero_grad()
if self.ema:
self.ema.update(self.model)
def preprocess_batch(self, batch):
"""
Allows custom preprocessing model inputs and ground truths depending on task type.
"""
return batch
def validate(self):
"""
Runs validation on test set using self.validator. The returned dict is expected to contain "fitness" key.
"""
metrics = self.validator(self)
fitness = metrics.pop('fitness', -self.loss.detach().cpu().numpy()) # use loss as fitness measure if not found
if not self.best_fitness or self.best_fitness < fitness:
self.best_fitness = fitness
return metrics, fitness
def get_model(self, cfg=None, weights=None, verbose=True):
"""Get model and raise NotImplementedError for loading cfg files."""
raise NotImplementedError("This task trainer doesn't support loading cfg files")
def get_validator(self):
"""Returns a NotImplementedError when the get_validator function is called."""
raise NotImplementedError('get_validator function not implemented in trainer')
def get_dataloader(self, dataset_path, batch_size=16, rank=0, mode='train'):
"""
Returns dataloader derived from torch.data.Dataloader.
"""
raise NotImplementedError('get_dataloader function not implemented in trainer')
def build_dataset(self, img_path, mode='train', batch=None):
"""Build dataset"""
raise NotImplementedError('build_dataset function not implemented in trainer')
def criterion(self, preds, batch):
"""
Returns loss and individual loss items as Tensor.
"""
raise NotImplementedError('criterion function not implemented in trainer')
def label_loss_items(self, loss_items=None, prefix='train'):
"""
Returns a loss dict with labelled training loss items tensor
"""
# Not needed for classification but necessary for segmentation & detection
return {'loss': loss_items} if loss_items is not None else ['loss']
def set_model_attributes(self):
"""
To set or update model parameters before training.
"""
self.model.names = self.data['names']
def build_targets(self, preds, targets):
"""Builds target tensors for training YOLO model."""
pass
def progress_string(self):
"""Returns a string describing training progress."""
return ''
# TODO: may need to put these following functions into callback
def plot_training_samples(self, batch, ni):
"""Plots training samples during YOLOv5 training."""
pass
def plot_training_labels(self):
"""Plots training labels for YOLO model."""
pass
def save_metrics(self, metrics):
"""Saves training metrics to a CSV file."""
keys, vals = list(metrics.keys()), list(metrics.values())
n = len(metrics) + 1 # number of cols
s = '' if self.csv.exists() else (('%23s,' * n % tuple(['epoch'] + keys)).rstrip(',') + '\n') # header
with open(self.csv, 'a') as f:
f.write(s + ('%23.5g,' * n % tuple([self.epoch] + vals)).rstrip(',') + '\n')
def plot_metrics(self):
"""Plot and display metrics visually."""
pass
def on_plot(self, name, data=None):
"""Registers plots (e.g. to be consumed in callbacks)"""
self.plots[name] = {'data': data, 'timestamp': time.time()}
def final_eval(self):
"""Performs final evaluation and validation for object detection YOLO model."""
for f in self.last, self.best:
if f.exists():
strip_optimizer(f) # strip optimizers
if f is self.best:
LOGGER.info(f'\nValidating {f}...')
self.metrics = self.validator(model=f)
self.metrics.pop('fitness', None)
self.run_callbacks('on_fit_epoch_end')
def check_resume(self):
"""Check if resume checkpoint exists and update arguments accordingly."""
resume = self.args.resume
if resume:
try:
exists = isinstance(resume, (str, Path)) and Path(resume).exists()
last = Path(check_file(resume) if exists else get_latest_run())
# Check that resume data YAML exists, otherwise strip to force re-download of dataset
ckpt_args = attempt_load_weights(last).args
if not Path(ckpt_args['data']).exists():
ckpt_args['data'] = self.args.data
self.args = get_cfg(ckpt_args)
self.args.model, resume = str(last), True # reinstate
except Exception as e:
raise FileNotFoundError('Resume checkpoint not found. Please pass a valid checkpoint to resume from, '
"i.e. 'yolo train resume model=path/to/last.pt'") from e
self.resume = resume
def resume_training(self, ckpt):
"""Resume YOLO training from given epoch and best fitness."""
if ckpt is None:
return
best_fitness = 0.0
start_epoch = ckpt['epoch'] + 1
if ckpt['optimizer'] is not None:
self.optimizer.load_state_dict(ckpt['optimizer']) # optimizer
best_fitness = ckpt['best_fitness']
if self.ema and ckpt.get('ema'):
self.ema.ema.load_state_dict(ckpt['ema'].float().state_dict()) # EMA
self.ema.updates = ckpt['updates']
if self.resume:
assert start_epoch > 0, \
f'{self.args.model} training to {self.epochs} epochs is finished, nothing to resume.\n' \
f"Start a new training without resuming, i.e. 'yolo train model={self.args.model}'"
LOGGER.info(
f'Resuming training from {self.args.model} from epoch {start_epoch + 1} to {self.epochs} total epochs')
if self.epochs < start_epoch:
LOGGER.info(
f"{self.model} has been trained for {ckpt['epoch']} epochs. Fine-tuning for {self.epochs} more epochs.")
self.epochs += ckpt['epoch'] # finetune additional epochs
self.best_fitness = best_fitness
self.start_epoch = start_epoch
if start_epoch > (self.epochs - self.args.close_mosaic):
LOGGER.info('Closing dataloader mosaic')
if hasattr(self.train_loader.dataset, 'mosaic'):
self.train_loader.dataset.mosaic = False
if hasattr(self.train_loader.dataset, 'close_mosaic'):
self.train_loader.dataset.close_mosaic(hyp=self.args)
@staticmethod
def build_optimizer(model, name='Adam', lr=0.001, momentum=0.9, decay=1e-5):
"""
Builds an optimizer with the specified parameters and parameter groups.
Args:
model (nn.Module): model to optimize
name (str): name of the optimizer to use
lr (float): learning rate
momentum (float): momentum
decay (float): weight decay
Returns:
optimizer (torch.optim.Optimizer): the built optimizer
"""
g = [], [], [] # optimizer parameter groups
bn = tuple(v for k, v in nn.__dict__.items() if 'Norm' in k) # normalization layers, i.e. BatchNorm2d()
for v in model.modules():
if hasattr(v, 'bias') and isinstance(v.bias, nn.Parameter): # bias (no decay)
g[2].append(v.bias)
if isinstance(v, bn): # weight (no decay)
g[1].append(v.weight)
elif hasattr(v, 'weight') and isinstance(v.weight, nn.Parameter): # weight (with decay)
g[0].append(v.weight)
if name == 'Adam':
optimizer = torch.optim.Adam(g[2], lr=lr, betas=(momentum, 0.999)) # adjust beta1 to momentum
elif name == 'AdamW':
optimizer = torch.optim.AdamW(g[2], lr=lr, betas=(momentum, 0.999), weight_decay=0.0)
elif name == 'RMSProp':
optimizer = torch.optim.RMSprop(g[2], lr=lr, momentum=momentum)
elif name == 'SGD':
optimizer = torch.optim.SGD(g[2], lr=lr, momentum=momentum, nesterov=True)
else:
raise NotImplementedError(f'Optimizer {name} not implemented.')
optimizer.add_param_group({'params': g[0], 'weight_decay': decay}) # add g0 with weight_decay
optimizer.add_param_group({'params': g[1], 'weight_decay': 0.0}) # add g1 (BatchNorm2d weights)
LOGGER.info(f"{colorstr('optimizer:')} {type(optimizer).__name__}(lr={lr}) with parameter groups "
f'{len(g[1])} weight(decay=0.0), {len(g[0])} weight(decay={decay}), {len(g[2])} bias')
return optimizer
def check_amp(model):
"""
This function checks the PyTorch Automatic Mixed Precision (AMP) functionality of a YOLOv8 model.
If the checks fail, it means there are anomalies with AMP on the system that may cause NaN losses or zero-mAP
results, so AMP will be disabled during training.
Args:
model (nn.Module): A YOLOv8 model instance.
Returns:
(bool): Returns True if the AMP functionality works correctly with YOLOv8 model, else False.
Raises:
AssertionError: If the AMP checks fail, indicating anomalies with the AMP functionality on the system.
"""
device = next(model.parameters()).device # get model device
if device.type in ('cpu', 'mps'):
return False # AMP only used on CUDA devices
def amp_allclose(m, im):
"""All close FP32 vs AMP results."""
a = m(im, device=device, verbose=False)[0].boxes.data # FP32 inference
with torch.cuda.amp.autocast(True):
b = m(im, device=device, verbose=False)[0].boxes.data # AMP inference
del m
return a.shape == b.shape and torch.allclose(a, b.float(), atol=0.5) # close to 0.5 absolute tolerance
f = ROOT / 'assets/bus.jpg' # image to check
im = f if f.exists() else 'https://ultralytics.com/images/bus.jpg' if ONLINE else np.ones((640, 640, 3))
prefix = colorstr('AMP: ')
LOGGER.info(f'{prefix}running Automatic Mixed Precision (AMP) checks with YOLOv8n...')
try:
from ultralytics import YOLO
assert amp_allclose(YOLO('yolov8n.pt'), im)
LOGGER.info(f'{prefix}checks passed ✅')
except ConnectionError:
LOGGER.warning(f"{prefix}checks skipped ⚠️, offline and unable to download YOLOv8n. Setting 'amp=True'.")
except AssertionError:
LOGGER.warning(f'{prefix}checks failed ❌. Anomalies were detected with AMP on your system that may lead to '
f'NaN losses or zero-mAP results, so AMP will be disabled during training.')
return False
return True