目录 前言 1. parse_opt函数 2. main函数 2.1 main函数打印关键词/安装环境 2.2 main函数是否进行断点训练 2.3 main函数是否分布式训练 2.4 main函数是否进化训练/遗传算法调参 3. train函数 3.1 trai
目录
- 前言
- 1. parse_opt函数
- 2. main函数
- 2.1 main函数——打印关键词/安装环境
- 2.2 main函数——是否进行断点训练
- 2.3 main函数——是否分布式训练
- 2.4 main函数——是否进化训练/遗传算法调参
- 3. train函数
- 3.1 train函数——基本配置信息
- 3.2 train函数——模型加载/断点训练
- 3.3 train函数——冻结训练/冻结层设置
- 3.4 train函数——图片大小/batchsize设置
- 3.5 train函数——优化器选择 / 分组优化设置
- 3.6 train函数——学习率/ema/归一化/单机多卡
- 3.7 train函数——数据加载 / anchor调整
- 3.8 train函数——训练配置/多尺度训练/热身训练
- 3.9 train函数——训练结束/打印信息/保存结果
- 4. run函数
- 5.全部代码注释
- 使用教程
- 总结
前言
最近在用yolov5参加比赛,yolov5的技巧很多,仅仅用来参加比赛,着实有点浪费,所以有必要好好学习一番,在认真学习之前,首先向yolov5的作者致敬,对了我是用的版本是v6。每每看到这些大神的作品,实在是有点惭愧,要学的太多了
1. parse_opt函数
def parse_opt(known=False): """ argparse 使用方法: parse = argparse.ArgumentParser() parse.add_argument('--s', type=int, default=2, help='flag_int') """ parser = argparse.ArgumentParser() # weights 权重的路径./weights/yolov5s.pt.... # yolov5提供4个不同深度不同宽度的预训练权重 用户可以根据自己的需求选择下载 parser.add_argument('--weights', type=str, default=ROOT / 'yolov5s.pt', help='initial weights path') # cfg 配置文件(网络结构) anchor/backbone/numclasses/head,训练自己的数据集需要自己生成 # 生成方式——例如我的yolov5s_mchar.yaml 根据自己的需求选择复制./models/下面.yaml文件,5个文件的区别在于模型的深度和宽度依次递增 parser.add_argument('--cfg', type=str, default='', help='model.yaml path') # data 数据集配置文件(路径) train/val/label/, 该文件需要自己生成 # 生成方式——例如我的/data/mchar.yaml 训练集和验证集的路径 + 类别数 + 类别名称 parser.add_argument('--data', type=str, default=ROOT / 'data/coco128.yaml', help='dataset.yaml path') # hpy超参数设置文件(lr/sgd/mixup)./data/hyps/下面有5个超参数设置文件,每个文件的超参数初始值有细微区别,用户可以根据自己的需求选择其中一个 parser.add_argument('--hyp', type=str, default=ROOT / 'data/hyps/hyp.scratch-low.yaml', help='hyperparameters path') # epochs 训练轮次, 默认轮次为300次 parser.add_argument('--epochs', type=int, default=300) # batchsize 训练批次, 默认bs=16 parser.add_argument('--batch-size', type=int, default=16, help='total batch size for all GPUs, -1 for autobatch') # imagesize 设置图片大小, 默认640*640 parser.add_argument('--imgsz', '--img', '--img-size', type=int, default=640, help='train, val image size (pixels)') # rect 是否采用矩形训练,默认为False parser.add_argument('--rect', action='store_true', help='rectangular training') # resume 是否接着上次的训练结果,继续训练 parser.add_argument('--resume', nargs='?', const=True, default=False, help='resume most recent training') # nosave 不保存模型 默认False(保存) 在./runs/exp*/train/weights/保存两个模型 一个是最后一次的模型 一个是最好的模型 # best.pt/ last.pt 不建议运行代码添加 --nosave parser.add_argument('--nosave', action='store_true', help='only save final checkpoint') # noval 最后进行测试, 设置了之后就是训练结束都测试一下, 不设置每轮都计算mAP, 建议不设置 parser.add_argument('--noval', action='store_true', help='only validate final epoch') # noautoanchor 不自动调整anchor, 默认False, 自动调整anchor parser.add_argument('--noautoanchor', action='store_true', help='disable AutoAnchor') # evolve参数进化, 遗传算法调参 parser.add_argument('--evolve', type=int, nargs='?', const=300, help='evolve hyperparameters for x generations') # bucket谷歌优盘 / 一般用不到 parser.add_argument('--bucket', type=str, default='', help='gsutil bucket') # cache 是否提前缓存图片到内存,以加快训练速度,默认False parser.add_argument('--cache', type=str, nargs='?', const='ram', help='--cache images in "ram" (default) or "disk"') # mage-weights 使用图片采样策略,默认不使用 parser.add_argument('--image-weights', action='store_true', help='use weighted image selection for training') # device 设备选择 parser.add_argument('--device', default='', help='cuda device, i.e. 0 or 0,1,2,3 or cpu') # multi-scale 多测度训练 parser.add_argument('--multi-scale', action='store_true', help='vary img-size +/- 50%%') # single-cls 数据集是否多类/默认True parser.add_argument('--single-cls', action='store_true', help='train multi-class data as single-class') # optimizer 优化器选择 / 提供了三种优化器 parser.add_argument('--optimizer', type=str, choices=['SGD', 'Adam', 'AdamW'], default='SGD', help='optimizer') # sync-bn:是否使用跨卡同步BN,在DDP模式使用 parser.add_argument('--sync-bn', action='store_true', help='use SyncBatchNorm, only available in DDP mode') # workers/dataloader的最大worker数量 parser.add_argument('--workers', type=int, default=8, help='max dataloader workers (per RANK in DDP mode)') # 保存路径 / 默认保存路径 ./runs/ train parser.add_argument('--project', default=ROOT / 'runs/train', help='save to project/name') # 实验名称 parser.add_argument('--name', default='exp', help='save to project/name') # 项目位置是否存在 / 默认是都不存在 parser.add_argument('--exist-ok', action='store_true', help='existing project/name ok, do not increment') parser.add_argument('--quad', action='store_true', help='quad dataloader') # cos-lr 余弦学习率 parser.add_argument('--cos-lr', action='store_true', help='cosine LR scheduler') # 标签平滑 / 默认不增强, 用户可以根据自己标签的实际情况设置这个参数,建议设置小一点 0.1 / 0.05 parser.add_argument('--label-smoothing', type=float, default=0.0, help='Label smoothing epsilon') # 早停止忍耐次数 / 100次不更新就停止训练 parser.add_argument('--patience', type=int, default=100, help='EarlyStopping patience (epochs without improvement)') # --freeze冻结训练 可以设置 default = [0] 数据量大的情况下,建议不设置这个参数 parser.add_argument('--freeze', nargs='+', type=int, default=[0], help='Freeze layers: backbone=10, first3=0 1 2') # --save-period 多少个epoch保存一下checkpoint parser.add_argument('--save-period', type=int, default=-1, help='Save checkpoint every x epochs (disabled if < 1)') # --local_rank 进程编号 / 多卡使用 parser.add_argument('--local_rank', type=int, default=-1, help='DDP parameter, do not modify') # Weights & Biases arguments # 在线可视化工具,类似于tensorboard工具,想了解这款工具可以查看https://zhuanlan.zhihu.com/p/266337608 parser.add_argument('--entity', default=None, help='W&B: Entity') # upload_dataset: 是否上传dataset到wandb tabel(将数据集作为交互式 dsviz表 在浏览器中查看、查询、筛选和分析数据集) 默认False parser.add_argument('--upload_dataset', nargs='?', const=True, default=False, help='W&B: Upload data, "val" option') # bbox_interval: 设置界框图像记录间隔 Set bounding-box image logging interval for W&B 默认-1 opt.epochs // 10 parser.add_argument('--bbox_interval', type=int, default=-1, help='W&B: Set bounding-box image logging interval') # 使用数据的版本 parser.add_argument('--artifact_alias', type=str, default='latest', help='W&B: Version of dataset artifact to use') # 传入的基本配置中没有的参数也不会报错# parse_args()和parse_known_args() # parse = argparse.ArgumentParser() # parse.add_argument('--s', type=int, default=2, help='flag_int') # parser.parse_args() / parse_args() opt = parser.parse_known_args()[0] if known else parser.parse_args() return opt
2. main函数
2.1 main函数——打印关键词/安装环境
def main(opt, callbacks=Callbacks()): ############################################### 1. Checks ################################################## if RANK in [-1, 0]: # 输出所有训练参数 / 参数以彩色的方式表现 print_args(FILE.stem, opt) # 检查代码版本是否更新 check_git_status() # 检查安装是否都安装了 requirements.txt, 缺少安装包安装。 # 缺少安装包:建议使用 pip install -i https://pypi.tuna.tsinghua.edu.cn/simple -r requirements.txt check_requirements(exclude=['thop'])
2.2 main函数——是否进行断点训练
############################################### 2. Resume ################################################## # 初始化可视化工具wandb,wandb使用教程看https://zhuanlan.zhihu.com/p/266337608 # 断点训练使用教程可以查看:https://blog.csdn.net/CharmsLUO/article/details/123410081 if opt.resume and not check_wandb_resume(opt) and not opt.evolve: # resume an interrupted run # isinstance()是否是已经知道的类型 # 如果resume是True,则通过get_lastest_run()函数找到runs为文件夹中最近的权重文件last.pt ckpt = opt.resume if isinstance(opt.resume, str) else get_latest_run() # specified or most recent path # 判断是否是文件 assert os.path.isfile(ckpt), 'ERROR: --resume checkpoint does not exist' # # 相关的opt参数也要替换成last.pt中的opt参数 safe_load()yaml文件加载数据 with open(Path(ckpt).parent.parent / 'opt.yaml', errors='ignore') as f: # argparse.Namespace 可以理解为字典 opt = argparse.Namespace(**yaml.safe_load(f)) # replace opt.cfg, opt.weights, opt.resume = '', ckpt, True # reinstate # 打印断点训练信息 LOGGER.info(f'Resuming training from {ckpt}') else: # 不使用断点训练就在加载输入的参数 opt.data, opt.cfg, opt.hyp, opt.weights, opt.project = \ check_file(opt.data), check_yaml(opt.cfg), check_yaml(opt.hyp), str(opt.weights), str(opt.project) # checks assert len(opt.cfg) or len(opt.weights), 'either --cfg or --weights must be specified' # opt.evolve=False,opt.name='exp' opt.evolve=True,opt.name='evolve' if opt.evolve: if opt.project == str(ROOT / 'runs/train'): # if default project name, rename to runs/evolve opt.project = str(ROOT / 'runs/evolve') opt.exist_ok, opt.resume = opt.resume, False # pass resume to exist_ok and disable resume # 保存相关信息 opt.save_dir = str(increment_path(Path(opt.project) / opt.name, exist_ok=opt.exist_ok))
2.3 main函数——是否分布式训练
# ############################################## 3.DDP mode ############################################### # 选择设备cpu/cuda device = select_device(opt.device, batch_size=opt.batch_size) # 多卡训练GPU if LOCAL_RANK != -1: msg = 'is not compatible with YOLOv5 Multi-GPU DDP training' assert not opt.image_weights, f'--image-weights {msg}' assert not opt.evolve, f'--evolve {msg}' assert opt.batch_size != -1, f'AutoBatch with --batch-size -1 {msg}, please pass a valid --batch-size' assert opt.batch_size % WORLD_SIZE == 0, f'--batch-size {opt.batch_size} must be multiple of WORLD_SIZE' assert torch.cuda.device_count() > LOCAL_RANK, 'insufficient CUDA devices for DDP command' # 根据编号选择设备 #使用torch.cuda.set_device()可以更方便地将模型和数据加载到对应GPU上, 直接定义模型之前加入一行代码即可 # torch.cuda.set_device(gpu_id) #单卡 # torch.cuda.set_device('cuda:'+str(gpu_ids)) #可指定多卡 torch.cuda.set_device(LOCAL_RANK) device = torch.device('cuda', LOCAL_RANK) # 初始化多进程 dist.init_process_group(backend="nccl" if dist.is_nccl_available() else "gloo")
2.4 main函数——是否进化训练/遗传算法调参
################################################ 4. Train ################################################# # 不设置evolve直接调用train训练 if not opt.evolve: train(opt.hyp, opt, device, callbacks) # 分布式训练 WORLD_SIZE=主机的数量 # 如果是使用多卡训练, 那么销毁进程组 if WORLD_SIZE > 1 and RANK == 0: LOGGER.info('Destroying process group... ') # 使用多卡训练, 那么销毁进程组 dist.destroy_process_group() # Evolve hyperparameters (optional) # 遗传净化算法/一边训练一遍进化 # 了解遗传算法可以查看我的博客: else: # Hyperparameter evolution metadata (mutation scale 0-1, lower_limit, upper_limit) # 超参数列表(突变范围 - 最小值 - 最大值) meta = {'lr0': (1, 1e-5, 1e-1), # initial learning rate (SGD=1E-2, Adam=1E-3) 'lrf': (1, 0.01, 1.0), # final OneCycleLR learning rate (lr0 * lrf) 'momentum': (0.3, 0.6, 0.98), # SGD momentum/Adam beta1 'weight_decay': (1, 0.0, 0.001), # optimizer weight decay 'warmup_epochs': (1, 0.0, 5.0), # warmup epochs (fractions ok) 'warmup_momentum': (1, 0.0, 0.95), # warmup initial momentum 'warmup_bias_lr': (1, 0.0, 0.2), # warmup initial bias lr 'box': (1, 0.02, 0.2), # box loss gain 'cls': (1, 0.2, 4.0), # cls loss gain 'cls_pw': (1, 0.5, 2.0), # cls BCELoss positive_weight 'obj': (1, 0.2, 4.0), # obj loss gain (scale with pixels) 'obj_pw': (1, 0.5, 2.0), # obj BCELoss positive_weight 'iou_t': (0, 0.1, 0.7), # IoU training threshold 'anchor_t': (1, 2.0, 8.0), # anchor-multiple threshold 'anchors': (2, 2.0, 10.0), # anchors per output grid (0 to ignore) 'fl_gamma': (0, 0.0, 2.0), # focal loss gamma (efficientDet default gamma=1.5) 'hsv_h': (1, 0.0, 0.1), # image HSV-Hue augmentation (fraction) 'hsv_s': (1, 0.0, 0.9), # image HSV-Saturation augmentation (fraction) 'hsv_v': (1, 0.0, 0.9), # image HSV-Value augmentation (fraction) 'degrees': (1, 0.0, 45.0), # image rotation (+/- deg) 'translate': (1, 0.0, 0.9), # image translation (+/- fraction) 'scale': (1, 0.0, 0.9), # image scale (+/- gain) 'shear': (1, 0.0, 10.0), # image shear (+/- deg) 'perspective': (0, 0.0, 0.001), # image perspective (+/- fraction), range 0-0.001 'flipud': (1, 0.0, 1.0), # image flip up-down (probability) 'fliplr': (0, 0.0, 1.0), # image flip left-right (probability) 'mosaic': (1, 0.0, 1.0), # image mixup (probability) 'mixup': (1, 0.0, 1.0), # image mixup (probability) 'copy_paste': (1, 0.0, 1.0)} # segment copy-paste (probability) with open(opt.hyp, errors='ignore') as f: # 加载yaml超参数 hyp = yaml.safe_load(f) # load hyps dict if 'anchors' not in hyp: # anchors commented in hyp.yaml hyp['anchors'] = 3 opt.noval, opt.nosave, save_dir = True, True, Path(opt.save_dir) # only val/save final epoch # ei = [isinstance(x, (int, float)) for x in hyp.values()] # evolvable indices # 保存进化的超参数列表 evolve_yaml, evolve_csv = save_dir / 'hyp_evolve.yaml', save_dir / 'evolve.csv' if opt.bucket: os.system(f'gsutil cp gs://{opt.bucket}/evolve.csv {evolve_csv}') # download evolve.csv if exists """ 遗传算法调参:遵循适者生存、优胜劣汰的法则,即寻优过程中保留有用的,去除无用的。 遗传算法需要提前设置4个参数: 群体大小/进化代数/交叉概率/变异概率 """ # 默认选择进化300代 for _ in range(opt.evolve): # generations to evolve if evolve_csv.exists(): # if evolve.csv exists: select best hyps and mutate # Select parent(s) # 进化方式--single / --weight parent = 'single' # parent selection method: 'single' or 'weighted' # 加载evolve.txt文件 x = np.loadtxt(evolve_csv, ndmin=2, delimiter=',', skiprows=1) # 选取进化结果代数 n = min(5, len(x)) # number of previous results to consider x = x[np.argsort(-fitness(x))][:n] # top n mutations # 根据resluts计算hyp权重 w = fitness(x) - fitness(x).min() + 1E-6 # weights (sum > 0) # 根据不同进化方式获得base hyp if parent == 'single' or len(x) == 1: # x = x[random.randint(0, n - 1)] # random selection x = x[random.choices(range(n), weights=w)[0]] # weighted selection elif parent == 'weighted': x = (x * w.reshape(n, 1)).sum(0) / w.sum() # weighted combination # Mutate # # 获取突变初始值 mp, s = 0.8, 0.2 # mutation probability, sigma npr = np.random npr.seed(int(time.time())) g = np.array([meta[k][0] for k in hyp.keys()]) # gains 0-1 ng = len(meta) v = np.ones(ng) # 设置突变 while all(v == 1): # mutate until a change occurs (prevent duplicates) # 将突变添加到base hyp上 # [i+7]是因为x中前7个数字为results的指标(P,R,mAP,F1,test_loss=(box,obj,cls)),之后才是超参数hyp v = (g * (npr.random(ng) < mp) * npr.randn(ng) * npr.random() * s + 1).clip(0.3, 3.0) for i, k in enumerate(hyp.keys()): # plt.hist(v.ravel(), 300) hyp[k] = float(x[i + 7] * v[i]) # mutate # Constrain to limits # 限制超参再规定范围 for k, v in meta.items(): hyp[k] = max(hyp[k], v[1]) # lower limit hyp[k] = min(hyp[k], v[2]) # upper limit hyp[k] = round(hyp[k], 5) # significant digits # Train mutation # 训练 使用突变后的参超 测试其效果 results = train(hyp.copy(), opt, device, callbacks) callbacks = Callbacks() # Write mutation results # Write mutation results # 将结果写入results 并将对应的hyp写到evolve.txt evolve.txt中每一行为一次进化的结果 # 每行前七个数字 (P, R, mAP, F1, test_losses(GIOU, obj, cls)) 之后为hyp # 保存hyp到yaml文件 print_mutation(results, hyp.copy(), save_dir, opt.bucket) # Plot results # 将结果可视化 / 输出保存信息 plot_evolve(evolve_csv) LOGGER.info(f'Hyperparameter evolution finished {opt.evolve} generations\n' f"Results saved to {colorstr('bold', save_dir)}\n" f'Usage example: $ python train.py --hyp {evolve_yaml}')
3. train函数
3.1 train函数——基本配置信息
################################################ 1. 传入参数/基本配置 ############################################# # opt传入的参数 save_dir, epochs, batch_size, weights, single_cls, evolve, data, cfg, resume, noval, nosave, workers, freeze = \ Path(opt.save_dir), opt.epochs, opt.batch_size, opt.weights, opt.single_cls, opt.evolve, opt.data, opt.cfg, \ opt.resume, opt.noval, opt.nosave, opt.workers, opt.freeze # Directories w = save_dir / 'weights' # weights dir # 新建文件夹 weights train evolve (w.parent if evolve else w).mkdir(parents=True, exist_ok=True) # make dir # 保存训练结果的目录 如runs/train/exp*/weights/last.pt last, best = w / 'last.pt', w / 'best.pt' # Hyperparameters # isinstance()是否是已知类型 if isinstance(hyp, str): with open(hyp, errors='ignore') as f: # 加载yaml文件 hyp = yaml.safe_load(f) # load hyps dict # 打印超参数 彩色字体 LOGGER.info(colorstr('hyperparameters: ') + ', '.join(f'{k}={v}' for k, v in hyp.items())) # Save run settings # 如果不使用进化训练 if not evolve: # safe_dump() python值转化为yaml序列化 with open(save_dir / 'hyp.yaml', 'w') as f: yaml.safe_dump(hyp, f, sort_keys=False) with open(save_dir / 'opt.yaml', 'w') as f: # vars(opt) 的作用是把数据类型是Namespace的数据转换为字典的形式。 yaml.safe_dump(vars(opt), f, sort_keys=False) # Loggers data_dict = None if RANK in [-1, 0]: loggers = Loggers(save_dir, weights, opt, hyp, LOGGER) # loggers instance if loggers.wandb: data_dict = loggers.wandb.data_dict if resume: weights, epochs, hyp, batch_size = opt.weights, opt.epochs, opt.hyp, opt.batch_size # Register actions for k in methods(loggers): callbacks.register_action(k, callback=getattr(loggers, k)) # Config 画图 plots = not evolve # create plots # GPU / CPU cuda = device.type != 'cpu' # 随机种子 init_seeds(1 + RANK) # 存在子进程-分布式训练 with torch_distributed_zero_first(LOCAL_RANK): data_dict = data_dict or check_dataset(data) # check if None # 训练集和验证集的位路径 train_path, val_path = data_dict['train'], data_dict['val'] # 设置类别 是否单类 nc = 1 if single_cls else int(data_dict['nc']) # number of classes # 类别对应的名称 names = ['item'] if single_cls and len(data_dict['names']) != 1 else data_dict['names'] # class names # 判断类别长度和文件是否对应 assert len(names) == nc, f'{len(names)} names found for nc={nc} dataset in {data}' # check # 当前数据集是否是coco数据集(80个类别) is_coco = isinstance(val_path, str) and val_path.endswith('coco/val2017.txt') # COCO dataset
3.2 train函数——模型加载/断点训练
################################################### 2. Model ########################################### # 检查文件后缀是否是.pt check_suffix(weights, '.pt') # check weights # 加载预训练权重 yolov5提供了5个不同的预训练权重,大家可以根据自己的模型选择预训练权重 pretrained = weights.endswith('.pt') if pretrained: # # torch_distributed_zero_first(RANK): 用于同步不同进程对数据读取的上下文管理器 with torch_distributed_zero_first(LOCAL_RANK): # 如果本地不存在就从网站上下载 weights = attempt_download(weights) # download if not found locally # 加载模型以及参数 ckpt = torch.load(weights, map_location='cpu') # load checkpoint to CPU to avoid CUDA memory leak """ 两种加载模型的方式: opt.cfg / ckpt['model'].yaml 使用resume-断点训练: 选择ckpt['model']yaml创建模型, 且不加载anchor 使用断点训练时,保存的模型会保存anchor,所以不需要加载 """ model = Model(cfg or ckpt['model'].yaml, ch=3, nc=nc, anchors=hyp.get('anchors')).to(device) # create exclude = ['anchor'] if (cfg or hyp.get('anchors')) and not resume else [] # exclude keys csd = ckpt['model'].float().state_dict() # checkpoint state_dict as FP32 # 筛选字典中的键值对 把exclude删除 csd = intersect_dicts(csd, model.state_dict(), exclude=exclude) # intersect model.load_state_dict(csd, strict=False) # load LOGGER.info(f'Transferred {len(csd)}/{len(model.state_dict())} items from {weights}') # report else: # 不适用预训练权重 model = Model(cfg, ch=3, nc=nc, anchors=hyp.get('anchors')).to(device) # create
3.3 train函数——冻结训练/冻结层设置
################################################ 3. Freeze/冻结训练 ######################################### # 冻结训练的网络层 freeze = [f'model.{x}.' for x in (freeze if len(freeze) > 1 else range(freeze[0]))] # layers to freeze for k, v in model.named_parameters(): v.requires_grad = True # train all layers if any(x in k for x in freeze): LOGGER.info(f'freezing {k}') # 冻结训练的层梯度不更新 v.requires_grad = False
3.4 train函数——图片大小/batchsize设置
# Image size gs = max(int(model.stride.max()), 32) # grid size (max stride) # 检查图片的大小 imgsz = check_img_size(opt.imgsz, gs, floor=gs * 2) # verify imgsz is gs-multiple # Batch size if RANK == -1 and batch_size == -1: # single-GPU only, estimate best batch size batch_size = check_train_batch_size(model, imgsz) loggers.on_params_update({"batch_size": batch_size})
3.5 train函数——优化器选择 / 分组优化设置
############################################ 4. Optimizer/优化器 ########################################### """ nbs = 64 batchsize = 16 accumulate = 64 / 16 = 4 模型梯度累计accumulate次之后就更新一次模型 相当于使用更大batch_size """ nbs = 64 # nominal batch size accumulate = max(round(nbs / batch_size), 1) # accumulate loss before optimizing # 权重衰减参数 hyp['weight_decay'] *= batch_size * accumulate / nbs # scale weight_decay # 打印日志 LOGGER.info(f"Scaled weight_decay = {hyp['weight_decay']}") # 将模型参数分为三组(weights、biases、bn)来进行分组优化 g0, g1, g2 = [], [], [] # optimizer parameter groups for v in model.modules(): if hasattr(v, 'bias') and isinstance(v.bias, nn.Parameter): # bias g2.append(v.bias) if isinstance(v, nn.BatchNorm2d): # weight (no decay) g0.append(v.weight) elif hasattr(v, 'weight') and isinstance(v.weight, nn.Parameter): # weight (with decay) g1.append(v.weight) # 选择优化器 / 提供了三个优化器——g0 if opt.optimizer == 'Adam': optimizer = Adam(g0, lr=hyp['lr0'], betas=(hyp['momentum'], 0.999)) # adjust beta1 to momentum elif opt.optimizer == 'AdamW': optimizer = AdamW(g0, lr=hyp['lr0'], betas=(hyp['momentum'], 0.999)) # adjust beta1 to momentum else: optimizer = SGD(g0, lr=hyp['lr0'], momentum=hyp['momentum'], nesterov=True) # 设置优化的方式——g1 / g2 optimizer.add_param_group({'params': g1, 'weight_decay': hyp['weight_decay']}) # add g1 with weight_decay optimizer.add_param_group({'params': g2}) # add g2 (biases) # 打印log日志 优化信息 LOGGER.info(f"{colorstr('optimizer:')} {type(optimizer).__name__} with parameter groups " f"{len(g0)} weight (no decay), {len(g1)} weight, {len(g2)} bias") # 删除变量 del g0, g1, g2
3.6 train函数——学习率/ema/归一化/单机多卡
############################################ 5. Scheduler ############################################## # 是否余弦学习率调整方式 if opt.cos_lr: lf = one_cycle(1, hyp['lrf'], epochs) # cosine 1->hyp['lrf'] else: lf = lambda x: (1 - x / epochs) * (1.0 - hyp['lrf']) + hyp['lrf'] # linear scheduler = lr_scheduler.LambdaLR(optimizer, lr_lambda=lf) # plot_lr_scheduler(optimizer, scheduler, epochs) # EMA # 使用EMA(指数移动平均)对模型的参数做平均, 一种给予近期数据更高权重的平均方法, 以求提高测试指标并增加模型鲁棒。 ema = ModelEMA(model) if RANK in [-1, 0] else None # Resume start_epoch, best_fitness = 0, 0.0 if pretrained: # Optimizer if ckpt['optimizer'] is not None: optimizer.load_state_dict(ckpt['optimizer']) best_fitness = ckpt['best_fitness'] # EMA if ema and ckpt.get('ema'): ema.ema.load_state_dict(ckpt['ema'].float().state_dict()) ema.updates = ckpt['updates'] # Epochs start_epoch = ckpt['epoch'] + 1 if resume: assert start_epoch > 0, f'{weights} training to {epochs} epochs is finished, nothing to resume.' if epochs < start_epoch: LOGGER.info(f"{weights} has been trained for {ckpt['epoch']} epochs. Fine-tuning for {epochs} more epochs.") epochs += ckpt['epoch'] # finetune additional epochs del ckpt, csd # DP mode # DP: 单机多卡模式 if cuda and RANK == -1 and torch.cuda.device_count() > 1: LOGGER.warning('WARNING: DP not recommended, use torch.distributed.run for best DDP Multi-GPU results.\n' 'See Multi-GPU Tutorial at https://github.com/ultralytics/yolov5/issues/475 to get started.') model = torch.nn.DataParallel(model) # SyncBatchNorm 多卡归一化 if opt.sync_bn and cuda and RANK != -1: model = torch.nn.SyncBatchNorm.convert_sync_batchnorm(model).to(device) # 打印信息 LOGGER.info('Using SyncBatchNorm()')
3.7 train函数——数据加载 / anchor调整
# ############################################## 6. Trainloader / 数据加载 ###################################### # 训练集数据加载 train_loader, dataset = create_dataloader(train_path, imgsz, batch_size // WORLD_SIZE, gs, single_cls, hyp=hyp, augment=True, cache=None if opt.cache == 'val' else opt.cache, rect=opt.rect, rank=LOCAL_RANK, workers=workers, image_weights=opt.image_weights, quad=opt.quad, prefix=colorstr('train: '), shuffle=True) # 标签编号最大值 mlc = int(np.concatenate(dataset.labels, 0)[:, 0].max()) # max label class # 类别总数 nb = len(train_loader) # number of batches # 判断编号是否正确 assert mlc < nc, f'Label class {mlc} exceeds nc={nc} in {data}. Possible class labels are 0-{nc - 1}' # Process 0 # 验证集数据集加载 if RANK in [-1, 0]: val_loader = create_dataloader(val_path, imgsz, batch_size // WORLD_SIZE * 2, gs, single_cls, hyp=hyp, cache=None if noval else opt.cache, rect=True, rank=-1, workers=workers * 2, pad=0.5, prefix=colorstr('val: '))[0] # 没有使用断点训练 if not resume: labels = np.concatenate(dataset.labels, 0) # c = torch.tensor(labels[:, 0]) # classes # cf = torch.bincount(c.long(), minlength=nc) + 1. # frequency # model._initialize_biases(cf.to(device)) if plots: # 画出标签信息 plot_labels(labels, names, save_dir) # Anchors # 自适应anchor / anchor可以理解为程序预测的box # 根据k-mean算法聚类生成新的锚框 if not opt.noautoanchor: # 参数dataset代表的是训练集,hyp['anchor_t']是从配置文件hpy.scratch.yaml读取的超参数 anchor_t:4.0 # 当配置文件中的anchor计算bpr(best possible recall)小于0.98时才会重新计算anchor。 # best possible recall最大值1,如果bpr小于0.98,程序会根据数据集的label自动学习anchor的尺寸 check_anchors(dataset, model=model, thr=hyp['anchor_t'], imgsz=imgsz) # 半进度 model.half().float() # pre-reduce anchor precision callbacks.run('on_pretrain_routine_end')
3.8 train函数——训练配置/多尺度训练/热身训练
# #################################################### 7. 训练 ############################################### # DDP mode # DDP:多机多卡 if cuda and RANK != -1: model = DDP(model, device_ids=[LOCAL_RANK], output_device=LOCAL_RANK) # Model attributes nl = de_parallel(model).model[-1].nl # number of detection layers (to scale hyps) hyp['box'] *= 3 / nl # scale to layers hyp['cls'] *= nc / 80 * 3 / nl # scale to classes and layers hyp['obj'] *= (imgsz / 640) ** 2 * 3 / nl # scale to image size and layers # 标签平滑 hyp['label_smoothing'] = opt.label_smoothing model.nc = nc # attach number of classes to model model.hyp = hyp # attach hyperparameters to model # 从训练样本标签得到类别权重(和类别中的目标数即类别频率成反比) model.class_weights = labels_to_class_weights(dataset.labels, nc).to(device) * nc # attach class weights model.names = names # Start training t0 = time.time() # # 获取热身迭代的次数iterations: 3 nw = max(round(hyp['warmup_epochs'] * nb), 100) # number of warmup iterations, max(3 epochs, 100 iterations) # nw = min(nw, (epochs - start_epoch) / 2 * nb) # limit warmup to < 1/2 of training last_opt_step = -1 # # 初始化maps(每个类别的map)和results maps = np.zeros(nc) # mAP per class results = (0, 0, 0, 0, 0, 0, 0) # P, R, mAP@.5, mAP@.5-.95, val_loss(box, obj, cls) # 设置学习率衰减所进行到的轮次,即使打断训练,使用resume接着训练也能正常衔接之前的训练进行学习率衰减 scheduler.last_epoch = start_epoch - 1 # do not move # 设置amp混合精度训练 scaler = amp.GradScaler(enabled=cuda) # 早停止,不更新结束训练 stopper = EarlyStopping(patience=opt.patience) # 初始化损失函数 compute_loss = ComputeLoss(model) # init loss class # 打印信息 LOGGER.info(f'Image sizes {imgsz} train, {imgsz} val\n' f'Using {train_loader.num_workers * WORLD_SIZE} dataloader workers\n' f"Logging results to {colorstr('bold', save_dir)}\n" f'Starting training for {epochs} epochs...') # 开始走起训练 for epoch in range(start_epoch, epochs): # epoch ------------------------------------------------------------------ model.train() # Update image weights (optional, single-GPU only) # opt.image_weights if opt.image_weights: """ 如果设置进行图片采样策略, 则根据前面初始化的图片采样权重model.class_weights以及maps配合每张图片包含的类别数 通过random.choices生成图片索引indices从而进行采样 """ cw = model.class_weights.cpu().numpy() * (1 - maps) ** 2 / nc # class weights iw = labels_to_image_weights(dataset.labels, nc=nc, class_weights=cw) # image weights dataset.indices = random.choices(range(dataset.n), weights=iw, k=dataset.n) # rand weighted idx # Update mosaic border (optional) # b = int(random.uniform(0.25 * imgsz, 0.75 * imgsz + gs) // gs * gs) # dataset.mosaic_border = [b - imgsz, -b] # height, width borders mloss = torch.zeros(3, device=device) # mean losses if RANK != -1: train_loader.sampler.set_epoch(epoch) pbar = enumerate(train_loader) LOGGER.info(('\n' + '%10s' * 7) % ('Epoch', 'gpu_mem', 'box', 'obj', 'cls', 'labels', 'img_size')) if RANK in [-1, 0]: # 进度条显示 pbar = tqdm(pbar, total=nb, bar_format='{l_bar}{bar:10}{r_bar}{bar:-10b}') # progress bar # 梯度清零 optimizer.zero_grad() for i, (imgs, targets, paths, _) in pbar: # batch ------------------------------------------------------------- ni = i + nb * epoch # number integrated batches (since train start) imgs = imgs.to(device, non_blocking=True).float() / 255 # uint8 to float32, 0-255 to 0.0-1.0 """ 热身训练(前nw次迭代) 在前nw次迭代中, 根据以下方式选取accumulate和学习率 """ # Warmup if ni <= nw: xi = [0, nw] # x interp # compute_loss.gr = np.interp(ni, xi, [0.0, 1.0]) # iou loss ratio (obj_loss = 1.0 or iou) accumulate = max(1, np.interp(ni, xi, [1, nbs / batch_size]).round()) for j, x in enumerate(optimizer.param_groups): """ bias的学习率从0.1下降到基准学习率lr*lf(epoch), 其他的参数学习率从0增加到lr*lf(epoch). lf为上面设置的余弦退火的衰减函数 动量momentum也从0.9慢慢变到hyp['momentum'](default=0.937) """ # bias lr falls from 0.1 to lr0, all other lrs rise from 0.0 to lr0 x['lr'] = np.interp(ni, xi, [hyp['warmup_bias_lr'] if j == 2 else 0.0, x['initial_lr'] * lf(epoch)]) if 'momentum' in x: x['momentum'] = np.interp(ni, xi, [hyp['warmup_momentum'], hyp['momentum']]) # Multi-scale if opt.multi_scale: """ Multi-scale 设置多尺度训练,从imgsz * 0.5, imgsz * 1.5 + gs随机选取尺寸 """ sz = random.randrange(imgsz * 0.5, imgsz * 1.5 + gs) // gs * gs # size sf = sz / max(imgs.shape[2:]) # scale factor if sf != 1: ns = [math.ceil(x * sf / gs) * gs for x in imgs.shape[2:]] # new shape (stretched to gs-multiple) imgs = nn.functional.interpolate(imgs, size=ns, mode='bilinear', align_corners=False) # Forward / 前向传播 with amp.autocast(enabled=cuda): pred = model(imgs) # forward # # 计算损失,包括分类损失,objectness损失,框的回归损失 # loss为总损失值,loss_items为一个元组,包含分类损失,objectness损失,框的回归损失和总损失 loss, loss_items = compute_loss(pred, targets.to(device)) # loss scaled by batch_size if RANK != -1: # 平均不同gpu之间的梯度 loss *= WORLD_SIZE # gradient averaged between devices in DDP mode if opt.quad: loss *= 4. # Backward scaler.scale(loss).backward() # Optimize # 模型反向传播accumulate次之后再根据累积的梯度更新一次参数 if ni - last_opt_step >= accumulate: scaler.step(optimizer) # optimizer.step scaler.update() optimizer.zero_grad() if ema: ema.update(model) last_opt_step = ni # Log if RANK in [-1, 0]: mloss = (mloss * i + loss_items) / (i + 1) # update mean losses mem = f'{torch.cuda.memory_reserved() / 1E9 if torch.cuda.is_available() else 0:.3g}G' # (GB) pbar.set_description(('%10s' * 2 + '%10.4g' * 5) % ( f'{epoch}/{epochs - 1}', mem, *mloss, targets.shape[0], imgs.shape[-1])) callbacks.run('on_train_batch_end', ni, model, imgs, targets, paths, plots, opt.sync_bn) if callbacks.stop_training: return # end batch ------------------------------------------------------------------------------------------------ # Scheduler 进行学习率衰减 lr = [x['lr'] for x in optimizer.param_groups] # for loggers scheduler.step() if RANK in [-1, 0]: # mAP callbacks.run('on_train_epoch_end', epoch=epoch) # 将model中的属性赋值给ema ema.update_attr(model, include=['yaml', 'nc', 'hyp', 'names', 'stride', 'class_weights']) # 判断当前的epoch是否是最后一轮 final_epoch = (epoch + 1 == epochs) or stopper.possible_stop # notest: 是否只测试最后一轮 True: 只测试最后一轮 False: 每轮训练完都测试mAP if not noval or final_epoch: # Calculate mAP """ 测试使用的是ema(指数移动平均 对模型的参数做平均)的模型 results: [1] Precision 所有类别的平均precision(最大f1时) [1] Recall 所有类别的平均recall [1] map@0.5 所有类别的平均mAP@0.5 [1] map@0.5:0.95 所有类别的平均mAP@0.5:0.95 [1] box_loss 验证集回归损失, obj_loss 验证集置信度损失, cls_loss 验证集分类损失 maps: [80] 所有类别的mAP@0.5:0.95 """ results, maps, _ = val.run(data_dict, batch_size=batch_size // WORLD_SIZE * 2, imgsz=imgsz, model=ema.ema, single_cls=single_cls, dataloader=val_loader, save_dir=save_dir, plots=False, callbacks=callbacks, compute_loss=compute_loss) # Update best mAP # Update best mAP 这里的best mAP其实是[P, R, mAP@.5, mAP@.5-.95]的一个加权值 # fi: [P, R, mAP@.5, mAP@.5-.95]的一个加权值 = 0.1*mAP@.5 + 0.9*mAP@.5-.95 fi = fitness(np.array(results).reshape(1, -1)) # weighted combination of [P, R, mAP@.5, mAP@.5-.95] if fi > best_fitness: best_fitness = fi log_vals = list(mloss) + list(results) + lr callbacks.run('on_fit_epoch_end', log_vals, epoch, best_fitness, fi) # Save model """ 保存带checkpoint的模型用于inference或resuming training 保存模型, 还保存了epoch, results, optimizer等信息 optimizer将不会在最后一轮完成后保存 model保存的是EMA的模型 """ if (not nosave) or (final_epoch and not evolve): # if save ckpt = {'epoch': epoch, 'best_fitness': best_fitness, 'model': deepcopy(de_parallel(model)).half(), 'ema': deepcopy(ema.ema).half(), 'updates': ema.updates, 'optimizer': optimizer.state_dict(), 'wandb_id': loggers.wandb.wandb_run.id if loggers.wandb else None, 'date': datetime.now().isoformat()} # Save last, best and delete torch.save(ckpt, last) if best_fitness == fi: torch.save(ckpt, best) if (epoch > 0) and (opt.save_period > 0) and (epoch % opt.save_period == 0): torch.save(ckpt, w / f'epoch{epoch}.pt') del ckpt callbacks.run('on_model_save', last, epoch, final_epoch, best_fitness, fi) # Stop Single-GPU if RANK == -1 and stopper(epoch=epoch, fitness=fi): break # Stop DDP TODO: known issues shttps://github.com/ultralytics/yolov5/pull/4576 # stop = stopper(epoch=epoch, fitness=fi) # if RANK == 0: # dist.broadcast_object_list([stop], 0) # broadcast 'stop' to all ranks # Stop DPP # with torch_distributed_zero_first(RANK): # if stop: # break # must break all DDP ranks
3.9 train函数——训练结束/打印信息/保存结果
############################################### 8. 打印训练信息 ########################################## if RANK in [-1, 0]: LOGGER.info(f'\n{epoch - start_epoch + 1} epochs completed in {(time.time() - t0) / 3600:.3f} hours.') for f in last, best: if f.exists(): # 模型训练完后, strip_optimizer函数将optimizer从ckpt中删除 # 并对模型进行model.half() 将Float32->Float16 这样可以减少模型大小, 提高inference速度 strip_optimizer(f) # strip optimizers if f is best: LOGGER.info(f'\nValidating {f}...') results, _, _ = val.run(data_dict, batch_size=batch_size // WORLD_SIZE * 2, imgsz=imgsz, model=attempt_load(f, device).half(), iou_thres=0.65 if is_coco else 0.60, # best pycocotools results at 0.65 single_cls=single_cls, dataloader=val_loader, save_dir=save_dir, save_json=is_coco, verbose=True, plots=True, callbacks=callbacks, compute_loss=compute_loss) # val best model with plots if is_coco: callbacks.run('on_fit_epoch_end', list(mloss) + list(results) + lr, epoch, best_fitness, fi) # 回调函数 callbacks.run('on_train_end', last, best, plots, epoch, results) LOGGER.info(f"Results saved to {colorstr('bold', save_dir)}") # 释放显存 torch.cuda.empty_cache() return results
4. run函数
def run(**kwargs): # 执行这个脚本/ 调用train函数 / 开启训练 # Usage: import train; train.run(data='coco128.yaml', imgsz=320, weights='yolov5m.pt') opt = parse_opt(True) for k, v in kwargs.items(): # setattr() 赋值属性,属性不存在则创建一个赋值 setattr(opt, k, v) main(opt) return opt
5.全部代码注释
# YOLOv5