import argparse
import time
import torch.distributed as dist
from torch.utils.data import DataLoader
import test # Import test.py to get mAP after each epoch
from models import *
from utils.datasets import *
from utils.utils import *
def train(
cfg,
data_cfg,
img_size=416,
resume=False,
epochs=273, # 500200 batches at bs 64, dataset length 117263
batch_size=16,
accumulate=1,
multi_scale=False,
freeze_backbone=False,
num_workers=4,
transfer=False # Transfer learning (train only YOLO layers)
):
weights = 'weights' + os.sep
latest = weights + 'latest.pt'
best = weights + 'best.pt'
device = torch_utils.select_device()
if multi_scale:
img_size = 608 # initiate with maximum multi_scale size
num_workers = 0 # bug https://github.com/ultralytics/yolov3/issues/174
else:
torch.backends.cudnn.benchmark = True # unsuitable for multiscale
# Configure run
train_path = parse_data_cfg(data_cfg)['train']
# Initialize model
model = Darknet(cfg, img_size).to(device)
# Optimizer
lr0 = 0.001 # initial learning rate
optimizer = torch.optim.SGD(model.parameters(), lr=lr0, momentum=0.9, weight_decay=0.0005)
cutoff = -1 # backbone reaches to cutoff layer
start_epoch = 0
best_loss = float('inf')
nf = int(model.module_defs[model.yolo_layers[0] - 1]['filters']) # yolo layer size (i.e. 255)
if resume: # Load previously saved model
if transfer: # Transfer learning
chkpt = torch.load(weights + 'yolov3-spp.pt', map_location=device)
model.load_state_dict({k: v for k, v in chkpt['model'].items() if v.numel() > 1 and v.shape[0] != 255},
strict=False)
for p in model.parameters():
p.requires_grad = True if p.shape[0] == nf else False
else: # resume from latest.pt
chkpt = torch.load(latest, map_location=device) # load checkpoint
model.load_state_dict(chkpt['model'])
start_epoch = chkpt['epoch'] + 1
if chkpt['optimizer'] is not None:
optimizer.load_state_dict(chkpt['optimizer'])
best_loss = chkpt['best_loss']
del chkpt
else: # Initialize model with backbone (optional)
if '-tiny.cfg' in cfg:
cutoff = load_darknet_weights(model, weights + 'yolov3-tiny.conv.15')
else:
cutoff = load_darknet_weights(model, weights + 'darknet53.conv.74')
# Scheduler (reduce lr at epochs 218, 245, i.e. batches 400k, 450k)
scheduler = torch.optim.lr_scheduler.MultiStepLR(optimizer, milestones=[218, 245], gamma=0.1,
last_epoch=start_epoch - 1)
# Dataset
dataset = LoadImagesAndLabels(train_path, img_size=img_size, augment=True)
# Initialize distributed training
if torch.cuda.device_count() > 1:
dist.init_process_group(backend=opt.backend, init_method=opt.dist_url, world_size=opt.world_size, rank=opt.rank)
model = torch.nn.parallel.DistributedDataParallel(model)
sampler = torch.utils.data.distributed.DistributedSampler(dataset)
else:
sampler = None
# Dataloader
dataloader = DataLoader(dataset,
batch_size=batch_size,
num_workers=num_workers,
shuffle=False,
pin_memory=True,
collate_fn=dataset.collate_fn,
sampler=sampler)
# Mixed precision training https://github.com/NVIDIA/apex
mixed_precision = False
if mixed_precision:
from apex import amp
model, optimizer = amp.initialize(model, optimizer, opt_level='O1')
# Start training
t = time.time()
model_info(model)
nB = len(dataloader)
n_burnin = min(round(nB / 5 + 1), 1000) # burn-in batches
os.remove('train_batch0.jpg') if os.path.exists('train_batch0.jpg') else None
os.remove('test_batch0.jpg') if os.path.exists('test_batch0.jpg') else None
for epoch in range(start_epoch, epochs):
model.train()
print(('\n%8s%12s' + '%10s' * 7) % ('Epoch', 'Batch', 'xy', 'wh', 'conf', 'cls', 'total', 'nTargets', 'time'))
# Update scheduler
scheduler.step()
# Freeze backbone at epoch 0, unfreeze at epoch 1
if freeze_backbone and epoch < 2:
for name, p in model.named_parameters():
if int(name.split('.')[1]) < cutoff: # if layer < 75
p.requires_grad = False if epoch == 0 else True
mloss = torch.zeros(5).to(device) # mean losses
for i, (imgs, targets, _, _) in enumerate(dataloader):
imgs = imgs.to(device)
targets = targets.to(device)
nt = len(targets)
# if nt == 0: # if no targets continue
# continue
# Plot images with bounding boxes
if epoch == 0 and i == 0:
plot_images(imgs=imgs, targets=targets, fname='train_batch0.jpg')
# SGD burn-in
if epoch == 0 and i <= n_burnin:
lr = lr0 * (i / n_burnin) ** 4
for x in optimizer.param_groups:
x['lr'] = lr
# Run model
pred = model(imgs)
# Build targets
target_list = build_targets(model, targets)
# Compute loss
loss, loss_items = compute_loss(pred, target_list)
# Compute gradient
if mixed_precision:
with amp.scale_loss(loss, optimizer) as scaled_loss:
scaled_loss.backward()
else:
loss.backward()
# Accumulate gradient for x batches before optimizing
if (i + 1) % accumulate == 0 or (i + 1) == nB:
optimizer.step()
optimizer.zero_grad()
# Update running mean of tracked metrics
mloss = (mloss * i + loss_items) / (i + 1)
# Print batch results
s = ('%8s%12s' + '%10.3g' * 7) % (
'%g/%g' % (epoch, epochs - 1),
'%g/%g' % (i, nB - 1), *mloss, nt, time.time() - t)
t = time.time()
print(s)
# Multi-Scale training (320 - 608 pixels) every 10 batches
if multi_scale and (i + 1) % 10 == 0:
dataset.img_size = random.choice(range(10, 20)) * 32
print('multi_scale img_size = %g' % dataset.img_size)
# Calculate mAP
with torch.no_grad():
results = test.test(cfg, data_cfg, batch_size=batch_size, img_size=img_size, model=model, conf_thres=0.1)
# Write epoch results
with open('results.txt', 'a') as file:
file.write(s + '%11.3g' * 5 % results + '\n') # P, R, mAP, F1, test_loss
# Update best loss
test_loss = results[4]
if test_loss < best_loss:
best_loss = test_loss
# Save training results
save = True and not opt.nosave
if save:
# Create checkpoint
chkpt = {'epoch': epoch,
'best_loss': best_loss,
'model': model.module.state_dict() if type(
model) is nn.parallel.DistributedDataParallel else model.state_dict(),
'optimizer': optimizer.state_dict()}
# Save latest checkpoint
torch.save(chkpt, latest)
# Save best checkpoint
if best_loss == test_loss:
torch.save(chkpt, best)
# Save backup every 10 epochs (optional)
if epoch > 0 and epoch % 10 == 0:
torch.save(chkpt, weights + 'backup%g.pt' % epoch)
# Delete checkpoint
del chkpt
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('--epochs', type=int, default=273, help='number of epochs')
parser.add_argument('--batch-size', type=int, default=16, help='size of each image batch')
parser.add_argument('--accumulate', type=int, default=1, help='accumulate gradient x batches before optimizing')
parser.add_argument('--cfg', type=str, default='cfg/yolov3-spp.cfg', help='cfg file path')
parser.add_argument('--data-cfg', type=str, default='data/coco.data', help='coco.data file path')
parser.add_argument('--multi-scale', action='store_true', help='random image sizes per batch 320 - 608')
parser.add_argument('--img-size', type=int, default=416, help='pixels')
parser.add_argument('--resume', action='store_true', help='resume training flag')
parser.add_argument('--transfer', action='store_true', help='transfer learning flag')
parser.add_argument('--num-workers', type=int, default=4, help='number of Pytorch DataLoader workers')
parser.add_argument('--dist-url', default='tcp://127.0.0.1:9999', type=str, help='distributed training init method')
parser.add_argument('--rank', default=0, type=int, help='distributed training node rank')
parser.add_argument('--world-size', default=1, type=int, help='number of nodes for distributed training')
parser.add_argument('--backend', default='nccl', type=str, help='distributed backend')
parser.add_argument('--nosave', action='store_true', help='do not save training results')
opt = parser.parse_args()
print(opt, end='\n\n')
init_seeds()
train(
opt.cfg,
opt.data_cfg,
img_size=opt.img_size,
resume=opt.resume or opt.transfer,
transfer=opt.transfer,
epochs=opt.epochs,
batch_size=opt.batch_size,
accumulate=opt.accumulate,
multi_scale=opt.multi_scale,
num_workers=opt.num_workers
)