train.py

# Ultralytics YOLOv5 🚀, AGPL-3.0 license
"""
Train a YOLOv5 model on a custom dataset. Models and datasets download automatically from the latest YOLOv5 release.

Usage - Single-GPU training:
    $ python train.py --data coco128.yaml --weights yolov5s.pt --img 640  # from pretrained (recommended)
    $ python train.py --data coco128.yaml --weights '' --cfg yolov5s.yaml --img 640  # from scratch

Usage - Multi-GPU DDP training:
    $ python -m torch.distributed.run --nproc_per_node 4 --master_port 1 train.py --data coco128.yaml --weights yolov5s.pt --img 640 --device 0,1,2,3

Models:     https://github.com/ultralytics/yolov5/tree/master/models
Datasets:   https://github.com/ultralytics/yolov5/tree/master/data
Tutorial:   https://docs.ultralytics.com/yolov5/tutorials/train_custom_data
"""

import argparse
import math
import os
import random
import subprocess
import sys
import time
from copy import deepcopy
from datetime import datetime, timedelta
from pathlib import Path

try:
    import comet_ml  # must be imported before torch (if installed)
except ImportError:
    comet_ml = None

import numpy as np
import torch
import torch.distributed as dist
import torch.nn as nn
import yaml
from torch.optim import lr_scheduler
from tqdm import tqdm

FILE = Path(__file__).resolve()
ROOT = FILE.parents[0]  # YOLOv5 root directory
if str(ROOT) not in sys.path:
    sys.path.append(str(ROOT))  # add ROOT to PATH
ROOT = Path(os.path.relpath(ROOT, Path.cwd()))  # relative

import val as validate  # for end-of-epoch mAP
from models.experimental import attempt_load
from models.yolo import Model
from utils.autoanchor import check_anchors
from utils.autobatch import check_train_batch_size
from utils.callbacks import Callbacks
from utils.dataloaders import create_dataloader
from utils.downloads import attempt_download, is_url
from utils.general import (
    LOGGER,
    TQDM_BAR_FORMAT,
    check_amp,
    check_dataset,
    check_file,
    check_git_info,
    check_git_status,
    check_img_size,
    check_requirements,
    check_suffix,
    check_yaml,
    colorstr,
    get_latest_run,
    increment_path,
    init_seeds,
    intersect_dicts,
    labels_to_class_weights,
    labels_to_image_weights,
    methods,
    one_cycle,
    print_args,
    print_mutation,
    strip_optimizer,
    yaml_save,
)
from utils.loggers import LOGGERS, Loggers
from utils.loggers.comet.comet_utils import check_comet_resume
from utils.loss import ComputeLoss
from utils.metrics import fitness
from utils.plots import plot_evolve
from utils.torch_utils import (
    EarlyStopping,
    ModelEMA,
    de_parallel,
    select_device,
    smart_DDP,
    smart_optimizer,
    smart_resume,
    torch_distributed_zero_first,
)

LOCAL_RANK = int(os.getenv("LOCAL_RANK", -1))  # https://pytorch.org/docs/stable/elastic/run.html
RANK = int(os.getenv("RANK", -1))
WORLD_SIZE = int(os.getenv("WORLD_SIZE", 1))
GIT_INFO = check_git_info()


def train(hyp, opt, device, callbacks):
    """
    Train a YOLOv5 model on a custom dataset using specified hyperparameters, options, and device, managing datasets,
    model architecture, loss computation, and optimizer steps.

    Args:
        hyp (str | dict): Path to the hyperparameters YAML file or a dictionary of hyperparameters.
        opt (argparse.Namespace): Parsed command-line arguments containing training options.
        device (torch.device): Device on which training occurs, e.g., 'cuda' or 'cpu'.
        callbacks (Callbacks): Callback functions for various training events.

    Returns:
        None

    Models and datasets download automatically from the latest YOLOv5 release.

    Example:
        Single-GPU training:
        ```bash
        $ python train.py --data coco128.yaml --weights yolov5s.pt --img 640  # from pretrained (recommended)
        $ python train.py --data coco128.yaml --weights '' --cfg yolov5s.yaml --img 640  # from scratch
        ```

        Multi-GPU DDP training:
        ```bash
        $ python -m torch.distributed.run --nproc_per_node 4 --master_port 1 train.py --data coco128.yaml --weights
        yolov5s.pt --img 640 --device 0,1,2,3
        ```

        For more usage details, refer to:
        - Models: https://github.com/ultralytics/yolov5/tree/master/models
        - Datasets: https://github.com/ultralytics/yolov5/tree/master/data
        - Tutorial: https://docs.ultralytics.com/yolov5/tutorials/train_custom_data
    """
    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,
    )
    callbacks.run("on_pretrain_routine_start")

    # Directories
    w = save_dir / "weights"  # weights dir
    (w.parent if evolve else w).mkdir(parents=True, exist_ok=True)  # make dir
    last, best = w / "last.pt", w / "best.pt"

    # Hyperparameters
    if isinstance(hyp, str):
        with open(hyp, errors="ignore") as f:
            hyp = yaml.safe_load(f)  # load hyps dict
    LOGGER.info(colorstr("hyperparameters: ") + ", ".join(f"{k}={v}" for k, v in hyp.items()))
    opt.hyp = hyp.copy()  # for saving hyps to checkpoints

    # Save run settings
    if not evolve:
        yaml_save(save_dir / "hyp.yaml", hyp)
        yaml_save(save_dir / "opt.yaml", vars(opt))

    # Loggers
    data_dict = None
    if RANK in {-1, 0}:
        include_loggers = list(LOGGERS)
        if getattr(opt, "ndjson_console", False):
            include_loggers.append("ndjson_console")
        if getattr(opt, "ndjson_file", False):
            include_loggers.append("ndjson_file")

        loggers = Loggers(
            save_dir=save_dir,
            weights=weights,
            opt=opt,
            hyp=hyp,
            logger=LOGGER,
            include=tuple(include_loggers),
        )

        # Register actions
        for k in methods(loggers):
            callbacks.register_action(k, callback=getattr(loggers, k))

        # Process custom dataset artifact link
        data_dict = loggers.remote_dataset
        if resume:  # If resuming runs from remote artifact
            weights, epochs, hyp, batch_size = opt.weights, opt.epochs, opt.hyp, opt.batch_size

    # Config
    plots = not evolve and not opt.noplots  # create plots
    cuda = device.type != "cpu"
    init_seeds(opt.seed + 1 + RANK, deterministic=True)
    with torch_distributed_zero_first(LOCAL_RANK):
        data_dict = data_dict or check_dataset(data)  # check if None
    train_path, val_path = data_dict["train"], data_dict["val"]
    nc = 1 if single_cls else int(data_dict["nc"])  # number of classes
    names = {0: "item"} if single_cls and len(data_dict["names"]) != 1 else data_dict["names"]  # class names
    is_coco = isinstance(val_path, str) and val_path.endswith("coco/val2017.txt")  # COCO dataset

    # Model
    check_suffix(weights, ".pt")  # check weights
    pretrained = weights.endswith(".pt")
    if pretrained:
        with torch_distributed_zero_first(LOCAL_RANK):
            weights = attempt_download(weights)  # download if not found locally
        ckpt = torch.load(weights, map_location="cpu")  # load checkpoint to CPU to avoid CUDA memory leak
        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
        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:
        model = Model(cfg, ch=3, nc=nc, anchors=hyp.get("anchors")).to(device)  # create
    amp = check_amp(model)  # check AMP

    # Freeze
    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
        # v.register_hook(lambda x: torch.nan_to_num(x))  # NaN to 0 (commented for erratic training results)
        if any(x in k for x in freeze):
            LOGGER.info(f"freezing {k}")
            v.requires_grad = False

    # Image size
    gs = max(int(model.stride.max()), 32)  # grid size (max stride)
    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, amp)
        loggers.on_params_update({"batch_size": batch_size})

    # Optimizer
    nbs = 64  # nominal batch size
    accumulate = max(round(nbs / batch_size), 1)  # accumulate loss before optimizing
    hyp["weight_decay"] *= batch_size * accumulate / nbs  # scale weight_decay
    optimizer = smart_optimizer(model, opt.optimizer, hyp["lr0"], hyp["momentum"], hyp["weight_decay"])

    # Scheduler
    if opt.cos_lr:
        lf = one_cycle(1, hyp["lrf"], epochs)  # cosine 1->hyp['lrf']
    else:

        def lf(x):
            """Linear learning rate scheduler function with decay calculated by epoch proportion."""
            return (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
    ema = ModelEMA(model) if RANK in {-1, 0} else None

    # Resume
    best_fitness, start_epoch = 0.0, 0
    if pretrained:
        if resume:
            best_fitness, start_epoch, epochs = smart_resume(ckpt, optimizer, ema, weights, epochs, resume)
        del ckpt, csd

    # DP mode
    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://docs.ultralytics.com/yolov5/tutorials/multi_gpu_training to get started."
        )
        model = torch.nn.DataParallel(model)

    # SyncBatchNorm
    if opt.sync_bn and cuda and RANK != -1:
        model = torch.nn.SyncBatchNorm.convert_sync_batchnorm(model).to(device)
        LOGGER.info("Using SyncBatchNorm()")

    # Trainloader
    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,
        seed=opt.seed,
    )
    labels = np.concatenate(dataset.labels, 0)
    mlc = int(labels[:, 0].max())  # max label class
    assert mlc < nc, f"Label class {mlc} exceeds nc={nc} in {data}. Possible class labels are 0-{nc - 1}"

    # Process 0
    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]

        if not resume:
            if not opt.noautoanchor:
                check_anchors(dataset, model=model, thr=hyp["anchor_t"], imgsz=imgsz)  # run AutoAnchor
            model.half().float()  # pre-reduce anchor precision

        callbacks.run("on_pretrain_routine_end", labels, names)

    # DDP mode
    if cuda and RANK != -1:
        model = smart_DDP(model)

    # 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
    hyp["label_smoothing"] = opt.label_smoothing
    model.nc = nc  # attach number of classes to model
    model.hyp = hyp  # attach hyperparameters to model
    model.class_weights = labels_to_class_weights(dataset.labels, nc).to(device) * nc  # attach class weights
    model.names = names

    # Start training
    t0 = time.time()
    nb = len(train_loader)  # number of batches
    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
    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)
    scheduler.last_epoch = start_epoch - 1  # do not move
    scaler = torch.cuda.amp.GradScaler(enabled=amp)
    stopper, stop = EarlyStopping(patience=opt.patience), False
    compute_loss = ComputeLoss(model)  # init loss class
    callbacks.run("on_train_start")
    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...'
    )
    for epoch in range(start_epoch, epochs):  # epoch ------------------------------------------------------------------
        callbacks.run("on_train_epoch_start")
        model.train()

        # Update image weights (optional, single-GPU only)
        if opt.image_weights:
            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" + "%11s" * 7) % ("Epoch", "GPU_mem", "box_loss", "obj_loss", "cls_loss", "Instances", "Size"))
        if RANK in {-1, 0}:
            pbar = tqdm(pbar, total=nb, bar_format=TQDM_BAR_FORMAT)  # progress bar
        optimizer.zero_grad()
        for i, (imgs, targets, paths, _) in pbar:  # batch -------------------------------------------------------------
            callbacks.run("on_train_batch_start")
            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

            # 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 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 == 0 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:
                sz = random.randrange(int(imgsz * 0.5), int(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
            with torch.cuda.amp.autocast(amp):
                pred = model(imgs)  # forward
                loss, loss_items = compute_loss(pred, targets.to(device))  # loss scaled by batch_size
                if RANK != -1:
                    loss *= WORLD_SIZE  # gradient averaged between devices in DDP mode
                if opt.quad:
                    loss *= 4.0

            # Backward
            scaler.scale(loss).backward()

            # Optimize - https://pytorch.org/docs/master/notes/amp_examples.html
            if ni - last_opt_step >= accumulate:
                scaler.unscale_(optimizer)  # unscale gradients
                torch.nn.utils.clip_grad_norm_(model.parameters(), max_norm=10.0)  # clip gradients
                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(
                    ("%11s" * 2 + "%11.4g" * 5)
                    % (f"{epoch}/{epochs - 1}", mem, *mloss, targets.shape[0], imgs.shape[-1])
                )
                callbacks.run("on_train_batch_end", model, ni, imgs, targets, paths, list(mloss))
                if callbacks.stop_training:
                    return
            # end batch ------------------------------------------------------------------------------------------------

        # Scheduler
        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)
            ema.update_attr(model, include=["yaml", "nc", "hyp", "names", "stride", "class_weights"])
            final_epoch = (epoch + 1 == epochs) or stopper.possible_stop
            if not noval or final_epoch:  # Calculate mAP
                results, maps, _ = validate.run(
                    data_dict,
                    batch_size=batch_size // WORLD_SIZE * 2,
                    imgsz=imgsz,
                    half=amp,
                    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
            fi = fitness(np.array(results).reshape(1, -1))  # weighted combination of [P, R, mAP@.5, mAP@.5-.95]
            stop = stopper(epoch=epoch, fitness=fi)  # early stop check
            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
            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(),
                    "opt": vars(opt),
                    "git": GIT_INFO,  # {remote, branch, commit} if a git repo
                    "date": datetime.now().isoformat(),
                }

                # Save last, best and delete
                torch.save(ckpt, last)
                if best_fitness == fi:
                    torch.save(ckpt, best)
                if 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)

        # EarlyStopping
        if RANK != -1:  # if DDP training
            broadcast_list = [stop if RANK == 0 else None]
            dist.broadcast_object_list(broadcast_list, 0)  # broadcast 'stop' to all ranks
            if RANK != 0:
                stop = broadcast_list[0]
        if stop:
            break  # must break all DDP ranks

        # end epoch ----------------------------------------------------------------------------------------------------
    # end training -----------------------------------------------------------------------------------------------------
    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():
                strip_optimizer(f)  # strip optimizers
                if f is best:
                    LOGGER.info(f"\nValidating {f}...")
                    results, _, _ = validate.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 at iou 0.65
                        single_cls=single_cls,
                        dataloader=val_loader,
                        save_dir=save_dir,
                        save_json=is_coco,
                        verbose=True,
                        plots=plots,
                        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)

        callbacks.run("on_train_end", last, best, epoch, results)

    torch.cuda.empty_cache()
    return results


def parse_opt(known=False):
    """
    Parse command-line arguments for YOLOv5 training, validation, and testing.

    Args:
        known (bool, optional): If True, parses known arguments, ignoring the unknown. Defaults to False.

    Returns:
        (argparse.Namespace): Parsed command-line arguments containing options for YOLOv5 execution.

    Example:
        ```python
        from ultralytics.yolo import parse_opt
        opt = parse_opt()
        print(opt)
        ```

    Links:
        - Models: https://github.com/ultralytics/yolov5/tree/master/models
        - Datasets: https://github.com/ultralytics/yolov5/tree/master/data
        - Tutorial: https://docs.ultralytics.com/yolov5/tutorials/train_custom_data
    """
    parser = argparse.ArgumentParser()
    # python train.py --weights yolov5s.pt --data data/pubg_player.yaml --name pubg --device cuda:0
    # 模型选择 不填表示从头开始训练 也可以指定模型进行训练
    # 这个参数是填写模型的。在default后面可以填写模型路径，下次训练就是在这个模型的基础上训练的。不过一般都是不填写，让它重新训练。
    parser.add_argument("--weights", type=str, default=ROOT / "yolov5s.pt", help="initial weights path")
    # 配置模型,--cfg：这个参数是用来选择模型参数的。一般是使用官方的，就是选择models文件夹下那4个文件中的一个。
    # 这4个文件每个特点都不同，具体差异可以去Github上看详细介绍。一般都是使用yolov5s.yaml，因为这个又小又快很适合完成小项目。
    parser.add_argument("--cfg", type=str, default="", help="model.yaml path")

    # 指定训练数据集.
    # --data：这个参数是用来指定数据集参数的。就是使用data文件夹里面的文件，但要使用的文件是自己定义的，这个地方需要注意。
    parser.add_argument("--data", type=str, default=ROOT / "data/pubg_player.yaml", help="dataset.yaml path")
    # 超参数
    parser.add_argument("--hyp", type=str, default=ROOT / "data/hyps/hyp.scratch-low.yaml", help="hyperparameters path")
    # 迭代次数500到1000次. --epochs：这个参数设置迭代次数。默认值为300，就是训练总次数。数值越高对显卡要求就越高。一般默认或者提高到500-1000.
    parser.add_argument("--epochs", type=int, default=100, help="total training epochs")
    # 一次对多少数据进行训练分数增大对显卡要求增益了。 --batch-size：每个轮次下图片训练的批次大小。同样对显卡的配置有要求。一般都是默认。
    parser.add_argument("--batch-size", type=int, default=16, help="total batch size for all GPUs, -1 for autobatch")
    # 图片缩放尺寸--imgsz：输入图像的分辨率大小，注意这里是训练和mAP测试的图像尺寸，而不是一个图像的宽高。一般默认。
    parser.add_argument("--imgsz", "--img", "--img-size", type=int, default=640, help="train, val image size (pixels)")
    parser.add_argument("--rect", action="store_true", help="rectangular training")
    # 可以修改这个参数来在以前的模型基础训练上但是需要原来的路径和文件.
    # --resume：这个参数是设置是否从上次一次没训练完的地方继续训练。但要求保留原文件。因为训练过程中会在run文件夹下生成对应的训练文件目录，这个参数要求这个训练文件目录还存在。
    # 例如：default=”runs/train/exp/weights/last.pt”（也可以写绝对路径），不使用的话就填False。
    parser.add_argument("--resume", nargs="?", const=True, default=False, help="resume most recent training")
    parser.add_argument("--nosave", action="store_true", help="only save final checkpoint")
    parser.add_argument("--noval", action="store_true", help="only validate final epoch")
    parser.add_argument("--noautoanchor", action="store_true", help="disable AutoAnchor")
    parser.add_argument("--noplots", action="store_true", help="save no plot files")
    # 调优方式
    parser.add_argument("--evolve", type=int, nargs="?", const=300, help="evolve hyperparameters for x generations")
    parser.add_argument(
        "--evolve_population", type=str, default=ROOT / "data/hyps", help="location for loading population"
    )
    parser.add_argument("--resume_evolve", type=str, default=None, help="resume evolve from last generation")
    parser.add_argument("--bucket", type=str, default="", help="gsutil bucket")
    parser.add_argument("--cache", type=str, nargs="?", const="ram", help="image --cache ram/disk")
    parser.add_argument("--image-weights", action="store_true", help="use weighted image selection for training")
    parser.add_argument("--device", default="", help="cuda device, i.e. 0 or 0,1,2,3 or cpu")
    parser.add_argument("--multi-scale", action="store_true", help="vary img-size +/- 50%%")
    parser.add_argument("--single-cls", action="store_true", help="train multi-class data as single-class")
    parser.add_argument("--optimizer", type=str, choices=["SGD", "Adam", "AdamW"], default="SGD", help="optimizer")
    parser.add_argument("--sync-bn", action="store_true", help="use SyncBatchNorm, only available in DDP mode")
    parser.add_argument("--workers", type=int, default=8, help="max dataloader workers (per RANK in DDP mode)")
    parser.add_argument("--project", default=ROOT / "runs/train", help="save to project/name")
    parser.add_argument("--name", default="exp", help="save to project/name")
    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")

    parser.add_argument("--cos-lr", action="store_true", help="cosine LR scheduler")
    parser.add_argument("--label-smoothing", type=float, default=0.0, help="Label smoothing epsilon")
    parser.add_argument("--patience", type=int, default=100, help="EarlyStopping patience (epochs without improvement)")
    parser.add_argument("--freeze", nargs="+", type=int, default=[0], help="Freeze layers: backbone=10, first3=0 1 2")
    parser.add_argument("--save-period", type=int, default=-1, help="Save checkpoint every x epochs (disabled if < 1)")
    parser.add_argument("--seed", type=int, default=0, help="Global training seed")
    parser.add_argument("--local_rank", type=int, default=-1, help="Automatic DDP Multi-GPU argument, do not modify")

    # Logger arguments
    parser.add_argument("--entity", default=None, help="Entity")
    parser.add_argument("--upload_dataset", nargs="?", const=True, default=False, help='Upload data, "val" option')
    parser.add_argument("--bbox_interval", type=int, default=-1, help="Set bounding-box image logging interval")
    parser.add_argument("--artifact_alias", type=str, default="latest", help="Version of dataset artifact to use")

    # NDJSON logging
    parser.add_argument("--ndjson-console", action="store_true", help="Log ndjson to console")
    parser.add_argument("--ndjson-file", action="store_true", help="Log ndjson to file")

    return parser.parse_known_args()[0] if known else parser.parse_args()


def main(opt, callbacks=Callbacks()):
    """
    Runs the main entry point for training or hyperparameter evolution with specified options and optional callbacks.

    Args:
        opt (argparse.Namespace): The command-line arguments parsed for YOLOv5 training and evolution.
        callbacks (ultralytics.utils.callbacks.Callbacks, optional): Callback functions for various training stages.
            Defaults to Callbacks().

    Returns:
        None

    Note:
        For detailed usage, refer to:
        https://github.com/ultralytics/yolov5/tree/master/models
    """
    if RANK in {-1, 0}:
        print_args(vars(opt))
        check_git_status()
        check_requirements(ROOT / "requirements.txt")

    # Resume (from specified or most recent last.pt)
    if opt.resume and not check_comet_resume(opt) and not opt.evolve:
        last = Path(check_file(opt.resume) if isinstance(opt.resume, str) else get_latest_run())
        opt_yaml = last.parent.parent / "opt.yaml"  # train options yaml
        opt_data = opt.data  # original dataset
        if opt_yaml.is_file():
            with open(opt_yaml, errors="ignore") as f:
                d = yaml.safe_load(f)
        else:
            d = torch.load(last, map_location="cpu")["opt"]
        opt = argparse.Namespace(**d)  # replace
        opt.cfg, opt.weights, opt.resume = "", str(last), True  # reinstate
        if is_url(opt_data):
            opt.data = check_file(opt_data)  # avoid HUB resume auth timeout
    else:
        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"
        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
        if opt.name == "cfg":
            opt.name = Path(opt.cfg).stem  # use model.yaml as name
        opt.save_dir = str(increment_path(Path(opt.project) / opt.name, exist_ok=opt.exist_ok))

    # DDP mode
    device = select_device(opt.device, batch_size=opt.batch_size)
    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"
        torch.cuda.set_device(LOCAL_RANK)
        device = torch.device("cuda", LOCAL_RANK)
        dist.init_process_group(
            backend="nccl" if dist.is_nccl_available() else "gloo", timeout=timedelta(seconds=10800)
        )

    # Train
    if not opt.evolve:
        train(opt.hyp, opt, device, callbacks)

    # Evolve hyperparameters (optional)
    else:
        # Hyperparameter evolution metadata (including this hyperparameter True-False, lower_limit, upper_limit)
        meta = {
            "lr0": (False, 1e-5, 1e-1),  # initial learning rate (SGD=1E-2, Adam=1E-3)
            "lrf": (False, 0.01, 1.0),  # final OneCycleLR learning rate (lr0 * lrf)
            "momentum": (False, 0.6, 0.98),  # SGD momentum/Adam beta1
            "weight_decay": (False, 0.0, 0.001),  # optimizer weight decay
            "warmup_epochs": (False, 0.0, 5.0),  # warmup epochs (fractions ok)
            "warmup_momentum": (False, 0.0, 0.95),  # warmup initial momentum
            "warmup_bias_lr": (False, 0.0, 0.2),  # warmup initial bias lr
            "box": (False, 0.02, 0.2),  # box loss gain
            "cls": (False, 0.2, 4.0),  # cls loss gain
            "cls_pw": (False, 0.5, 2.0),  # cls BCELoss positive_weight
            "obj": (False, 0.2, 4.0),  # obj loss gain (scale with pixels)
            "obj_pw": (False, 0.5, 2.0),  # obj BCELoss positive_weight
            "iou_t": (False, 0.1, 0.7),  # IoU training threshold
            "anchor_t": (False, 2.0, 8.0),  # anchor-multiple threshold
            "anchors": (False, 2.0, 10.0),  # anchors per output grid (0 to ignore)
            "fl_gamma": (False, 0.0, 2.0),  # focal loss gamma (efficientDet default gamma=1.5)
            "hsv_h": (True, 0.0, 0.1),  # image HSV-Hue augmentation (fraction)
            "hsv_s": (True, 0.0, 0.9),  # image HSV-Saturation augmentation (fraction)
            "hsv_v": (True, 0.0, 0.9),  # image HSV-Value augmentation (fraction)
            "degrees": (True, 0.0, 45.0),  # image rotation (+/- deg)
            "translate": (True, 0.0, 0.9),  # image translation (+/- fraction)
            "scale": (True, 0.0, 0.9),  # image scale (+/- gain)
            "shear": (True, 0.0, 10.0),  # image shear (+/- deg)
            "perspective": (True, 0.0, 0.001),  # image perspective (+/- fraction), range 0-0.001
            "flipud": (True, 0.0, 1.0),  # image flip up-down (probability)
            "fliplr": (True, 0.0, 1.0),  # image flip left-right (probability)
            "mosaic": (True, 0.0, 1.0),  # image mixup (probability)
            "mixup": (True, 0.0, 1.0),  # image mixup (probability)
            "copy_paste": (True, 0.0, 1.0),
        }  # segment copy-paste (probability)

        # GA configs
        pop_size = 50
        mutation_rate_min = 0.01
        mutation_rate_max = 0.5
        crossover_rate_min = 0.5
        crossover_rate_max = 1
        min_elite_size = 2
        max_elite_size = 5
        tournament_size_min = 2
        tournament_size_max = 10

        with open(opt.hyp, errors="ignore") as f:
            hyp = yaml.safe_load(f)  # load hyps dict
            if "anchors" not in hyp:  # anchors commented in hyp.yaml
                hyp["anchors"] = 3
        if opt.noautoanchor:
            del hyp["anchors"], meta["anchors"]
        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
        evolve_yaml, evolve_csv = save_dir / "hyp_evolve.yaml", save_dir / "evolve.csv"
        if opt.bucket:
            # download evolve.csv if exists
            subprocess.run(
                [
                    "gsutil",
                    "cp",
                    f"gs://{opt.bucket}/evolve.csv",
                    str(evolve_csv),
                ]
            )

        # Delete the items in meta dictionary whose first value is False
        del_ = [item for item, value_ in meta.items() if value_[0] is False]
        hyp_GA = hyp.copy()  # Make a copy of hyp dictionary
        for item in del_:
            del meta[item]  # Remove the item from meta dictionary
            del hyp_GA[item]  # Remove the item from hyp_GA dictionary

        # Set lower_limit and upper_limit arrays to hold the search space boundaries
        lower_limit = np.array([meta[k][1] for k in hyp_GA.keys()])
        upper_limit = np.array([meta[k][2] for k in hyp_GA.keys()])

        # Create gene_ranges list to hold the range of values for each gene in the population
        gene_ranges = [(lower_limit[i], upper_limit[i]) for i in range(len(upper_limit))]

        # Initialize the population with initial_values or random values
        initial_values = []

        # If resuming evolution from a previous checkpoint
        if opt.resume_evolve is not None:
            assert os.path.isfile(ROOT / opt.resume_evolve), "evolve population path is wrong!"
            with open(ROOT / opt.resume_evolve, errors="ignore") as f:
                evolve_population = yaml.safe_load(f)
                for value in evolve_population.values():
                    value = np.array([value[k] for k in hyp_GA.keys()])
                    initial_values.append(list(value))

        # If not resuming from a previous checkpoint, generate initial values from .yaml files in opt.evolve_population
        else:
            yaml_files = [f for f in os.listdir(opt.evolve_population) if f.endswith(".yaml")]
            for file_name in yaml_files:
                with open(os.path.join(opt.evolve_population, file_name)) as yaml_file:
                    value = yaml.safe_load(yaml_file)
                    value = np.array([value[k] for k in hyp_GA.keys()])
                    initial_values.append(list(value))

        # Generate random values within the search space for the rest of the population
        if initial_values is None:
            population = [generate_individual(gene_ranges, len(hyp_GA)) for _ in range(pop_size)]
        elif pop_size > 1:
            population = [generate_individual(gene_ranges, len(hyp_GA)) for _ in range(pop_size - len(initial_values))]
            for initial_value in initial_values:
                population = [initial_value] + population

        # Run the genetic algorithm for a fixed number of generations
        list_keys = list(hyp_GA.keys())
        for generation in range(opt.evolve):
            if generation >= 1:
                save_dict = {}
                for i in range(len(population)):
                    little_dict = {list_keys[j]: float(population[i][j]) for j in range(len(population[i]))}
                    save_dict[f"gen{str(generation)}number{str(i)}"] = little_dict

                with open(save_dir / "evolve_population.yaml", "w") as outfile:
                    yaml.dump(save_dict, outfile, default_flow_style=False)

            # Adaptive elite size
            elite_size = min_elite_size + int((max_elite_size - min_elite_size) * (generation / opt.evolve))
            # Evaluate the fitness of each individual in the population
            fitness_scores = []
            for individual in population:
                for key, value in zip(hyp_GA.keys(), individual):
                    hyp_GA[key] = value
                hyp.update(hyp_GA)
                results = train(hyp.copy(), opt, device, callbacks)
                callbacks = Callbacks()
                # Write mutation results
                keys = (
                    "metrics/precision",
                    "metrics/recall",
                    "metrics/mAP_0.5",
                    "metrics/mAP_0.5:0.95",
                    "val/box_loss",
                    "val/obj_loss",
                    "val/cls_loss",
                )
                print_mutation(keys, results, hyp.copy(), save_dir, opt.bucket)
                fitness_scores.append(results[2])

            # Select the fittest individuals for reproduction using adaptive tournament selection
            selected_indices = []
            for _ in range(pop_size - elite_size):
                # Adaptive tournament size
                tournament_size = max(
                    max(2, tournament_size_min),
                    int(min(tournament_size_max, pop_size) - (generation / (opt.evolve / 10))),
                )
                # Perform tournament selection to choose the best individual
                tournament_indices = random.sample(range(pop_size), tournament_size)
                tournament_fitness = [fitness_scores[j] for j in tournament_indices]
                winner_index = tournament_indices[tournament_fitness.index(max(tournament_fitness))]
                selected_indices.append(winner_index)

            # Add the elite individuals to the selected indices
            elite_indices = [i for i in range(pop_size) if fitness_scores[i] in sorted(fitness_scores)[-elite_size:]]
            selected_indices.extend(elite_indices)
            # Create the next generation through crossover and mutation
            next_generation = []
            for _ in range(pop_size):
                parent1_index = selected_indices[random.randint(0, pop_size - 1)]
                parent2_index = selected_indices[random.randint(0, pop_size - 1)]
                # Adaptive crossover rate
                crossover_rate = max(
                    crossover_rate_min, min(crossover_rate_max, crossover_rate_max - (generation / opt.evolve))
                )
                if random.uniform(0, 1) < crossover_rate:
                    crossover_point = random.randint(1, len(hyp_GA) - 1)
                    child = population[parent1_index][:crossover_point] + population[parent2_index][crossover_point:]
                else:
                    child = population[parent1_index]
                # Adaptive mutation rate
                mutation_rate = max(
                    mutation_rate_min, min(mutation_rate_max, mutation_rate_max - (generation / opt.evolve))
                )
                for j in range(len(hyp_GA)):
                    if random.uniform(0, 1) < mutation_rate:
                        child[j] += random.uniform(-0.1, 0.1)
                        child[j] = min(max(child[j], gene_ranges[j][0]), gene_ranges[j][1])
                next_generation.append(child)
            # Replace the old population with the new generation
            population = next_generation
        # Print the best solution found
        best_index = fitness_scores.index(max(fitness_scores))
        best_individual = population[best_index]
        print("Best solution found:", best_individual)
        # Plot results
        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}'
        )


def generate_individual(input_ranges, individual_length):
    """
    Generate an individual with random hyperparameters within specified ranges.

    Args:
        input_ranges (list[tuple[float, float]]): List of tuples where each tuple contains the lower and upper bounds
            for the corresponding gene (hyperparameter).
        individual_length (int): The number of genes (hyperparameters) in the individual.

    Returns:
        list[float]: A list representing a generated individual with random gene values within the specified ranges.

    Example:
        ```python
        input_ranges = [(0.01, 0.1), (0.1, 1.0), (0.9, 2.0)]
        individual_length = 3
        individual = generate_individual(input_ranges, individual_length)
        print(individual)  # Output: [0.035, 0.678, 1.456] (example output)
        ```

    Note:
        The individual returned will have a length equal to `individual_length`, with each gene value being a floating-point
        number within its specified range in `input_ranges`.
    """
    individual = []
    for i in range(individual_length):
        lower_bound, upper_bound = input_ranges[i]
        individual.append(random.uniform(lower_bound, upper_bound))
    return individual


def run(**kwargs):
    """
    Execute YOLOv5 training with specified options, allowing optional overrides through keyword arguments.

    Args:
        weights (str, optional): Path to initial weights. Defaults to ROOT / 'yolov5s.pt'.
        cfg (str, optional): Path to model YAML configuration. Defaults to an empty string.
        data (str, optional): Path to dataset YAML configuration. Defaults to ROOT / 'data/coco128.yaml'.
        hyp (str, optional): Path to hyperparameters YAML configuration. Defaults to ROOT / 'data/hyps/hyp.scratch-low.yaml'.
        epochs (int, optional): Total number of training epochs. Defaults to 100.
        batch_size (int, optional): Total batch size for all GPUs. Use -1 for automatic batch size determination. Defaults to 16.
        imgsz (int, optional): Image size (pixels) for training and validation. Defaults to 640.
        rect (bool, optional): Use rectangular training. Defaults to False.
        resume (bool | str, optional): Resume most recent training with an optional path. Defaults to False.
        nosave (bool, optional): Only save the final checkpoint. Defaults to False.
        noval (bool, optional): Only validate at the final epoch. Defaults to False.
        noautoanchor (bool, optional): Disable AutoAnchor. Defaults to False.
        noplots (bool, optional): Do not save plot files. Defaults to False.
        evolve (int, optional): Evolve hyperparameters for a specified number of generations. Use 300 if provided without a
            value.
        evolve_population (str, optional): Directory for loading population during evolution. Defaults to ROOT / 'data/ hyps'.
        resume_evolve (str, optional): Resume hyperparameter evolution from the last generation. Defaults to None.
        bucket (str, optional): gsutil bucket for saving checkpoints. Defaults to an empty string.
        cache (str, optional): Cache image data in 'ram' or 'disk'. Defaults to None.
        image_weights (bool, optional): Use weighted image selection for training. Defaults to False.
        device (str, optional): CUDA device identifier, e.g., '0', '0,1,2,3', or 'cpu'. Defaults to an empty string.
        multi_scale (bool, optional): Use multi-scale training, varying image size by ±50%. Defaults to False.
        single_cls (bool, optional): Train with multi-class data as single-class. Defaults to False.
        optimizer (str, optional): Optimizer type, choices are ['SGD', 'Adam', 'AdamW']. Defaults to 'SGD'.
        sync_bn (bool, optional): Use synchronized BatchNorm, only available in DDP mode. Defaults to False.
        workers (int, optional): Maximum dataloader workers per rank in DDP mode. Defaults to 8.
        project (str, optional): Directory for saving training runs. Defaults to ROOT / 'runs/train'.
        name (str, optional): Name for saving the training run. Defaults to 'exp'.
        exist_ok (bool, optional): Allow existing project/name without incrementing. Defaults to False.
        quad (bool, optional): Use quad dataloader. Defaults to False.
        cos_lr (bool, optional): Use cosine learning rate scheduler. Defaults to False.
        label_smoothing (float, optional): Label smoothing epsilon value. Defaults to 0.0.
        patience (int, optional): Patience for early stopping, measured in epochs without improvement. Defaults to 100.
        freeze (list, optional): Layers to freeze, e.g., backbone=10, first 3 layers = [0, 1, 2]. Defaults to [0].
        save_period (int, optional): Frequency in epochs to save checkpoints. Disabled if < 1. Defaults to -1.
        seed (int, optional): Global training random seed. Defaults to 0.
        local_rank (int, optional): Automatic DDP Multi-GPU argument. Do not modify. Defaults to -1.

    Returns:
        None: The function initiates YOLOv5 training or hyperparameter evolution based on the provided options.

    Examples:
        ```python
        import train
        train.run(data='coco128.yaml', imgsz=320, weights='yolov5m.pt')
        ```

    Notes:
        - Models: https://github.com/ultralytics/yolov5/tree/master/models
        - Datasets: https://github.com/ultralytics/yolov5/tree/master/data
        - Tutorial: https://docs.ultralytics.com/yolov5/tutorials/train_custom_data
    """
    opt = parse_opt(True)
    for k, v in kwargs.items():
        setattr(opt, k, v)
    main(opt)
    return opt


if __name__ == "__main__":
    opt = parse_opt()
    main(opt)