# 20分钟了解 MMAction2 框架设计 在本教程中，我们将通过一个视频动作识别的手把手教程来演示 `MMACTION2 1.0` 的整体架构。 本教程的目录如下: - [20分钟了解 MMAction2 框架设计](#20分钟了解-mmaction2-框架设计) - [步骤0：准备数据](#步骤0准备数据) - [步骤1：构建一个数据流水线](#步骤1构建一个数据流水线) - [步骤2：构建一个数据集和数据加载器](#步骤2构建一个数据集和数据加载器) - [步骤3：构建一个识别器](#步骤3构建一个识别器) - [步骤4：构建一个评估指标](#步骤4构建一个评估指标) - [步骤5：使用本地 PyTorch 训练和测试](#步骤5使用本地-pytorch-训练和测试) - [步骤6：使用 MMEngine 训练和测试（推荐）](#步骤6使用-mmengine-训练和测试推荐) 首先，我们需要初始化注册表的 `scope` ，以确保每个模块都在 `mmaction` 范围下注册。有关注册表的更多详细信息，请参考[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/advanced_tutorials/registry.html) 。 ```python from mmaction.utils import register_all_modules register_all_modules(init_default_scope=True) ``` ## 步骤0：准备数据 请下载我们准备的[精简版 kinetics400](https://download.openmmlab.com/mmaction/kinetics400_tiny.zip) 数据集，并将其提取到 `$MMACTION2/data` 目录。 解压后的目录结构应如下所示: ``` mmaction2 ├── data │ ├── kinetics400_tiny │ │ ├── kinetics_tiny_train_video.txt │ │ ├── kinetics_tiny_val_video.txt │ │ ├── train │ │ │ ├── 27_CSXByd3s.mp4 │ │ │ ├── 34XczvTaRiI.mp4 │ │ │ ├── A-wiliK50Zw.mp4 │ │ │ ├── ... │ │ └── val │ │ ├── 0pVGiAU6XEA.mp4 │ │ ├── AQrbRSnRt8M.mp4 │ │ ├── ... ``` 以下是标注文件 `kinetics_tiny_train_video.txt` 中的一些示例: ``` D32_1gwq35E.mp4 0 iRuyZSKhHRg.mp4 1 oXy-e_P_cAI.mp4 0 34XczvTaRiI.mp4 1 h2YqqUhnR34.mp4 0 ``` 文件中的每一行表示每一个视频的标注，其中第一项表示视频文件名(如 `D32_1gwq35E.mp4` )，第二项表示相应的标签(如 `D32_1gwq35E.mp4` 的标签是 `0` )。在这个数据集中，只有 `两个` 类别。 ## 步骤1：构建一个数据流水线 为了实现 `解码`、`采样`、`调整大小`、`裁剪`、`格式化` 和 `打包` 视频数据和相应的标签，我们需要设计一个数据流水线来处理这些过程。具体来说，我们设计了7个 `Transform` 类来构建这个视频处理流水线。注意，OpenMMLab 中的所有`Transform` 类都必须继承自 `mmcv` 中的 `BaseTransform` 类，实现抽象方法 `transform`，并注册到 `TRANSFORMS` 注册表。有关数据转换的更多详细信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/advanced_tutorials/data_transform.html) 。 ```python import mmcv import decord import numpy as np from mmcv.transforms import TRANSFORMS, BaseTransform, to_tensor from mmaction.structures import ActionDataSample @TRANSFORMS.register_module() class VideoInit(BaseTransform): def transform(self, results): container = decord.VideoReader(results['filename']) results['total_frames'] = len(container) results['video_reader'] = container return results @TRANSFORMS.register_module() class VideoSample(BaseTransform): def __init__(self, clip_len, num_clips, test_mode=False): self.clip_len = clip_len self.num_clips = num_clips self.test_mode = test_mode def transform(self, results): total_frames = results['total_frames'] interval = total_frames // self.clip_len if self.test_mode: # 使测试期间的采样具有确定性 np.random.seed(42) inds_of_all_clips = [] for i in range(self.num_clips): bids = np.arange(self.clip_len) * interval offset = np.random.randint(interval, size=bids.shape) inds = bids + offset inds_of_all_clips.append(inds) results['frame_inds'] = np.concatenate(inds_of_all_clips) results['clip_len'] = self.clip_len results['num_clips'] = self.num_clips return results @TRANSFORMS.register_module() class VideoDecode(BaseTransform): def transform(self, results): frame_inds = results['frame_inds'] container = results['video_reader'] imgs = container.get_batch(frame_inds).asnumpy() imgs = list(imgs) results['video_reader'] = None del container results['imgs'] = imgs results['img_shape'] = imgs[0].shape[:2] return results @TRANSFORMS.register_module() class VideoResize(BaseTransform): def __init__(self, r_size): self.r_size = (np.inf, r_size) def transform(self, results): img_h, img_w = results['img_shape'] new_w, new_h = mmcv.rescale_size((img_w, img_h), self.r_size) imgs = [mmcv.imresize(img, (new_w, new_h)) for img in results['imgs']] results['imgs'] = imgs results['img_shape'] = imgs[0].shape[:2] return results @TRANSFORMS.register_module() class VideoCrop(BaseTransform): def __init__(self, c_size): self.c_size = c_size def transform(self, results): img_h, img_w = results['img_shape'] center_x, center_y = img_w // 2, img_h // 2 x1, x2 = center_x - self.c_size // 2, center_x + self.c_size // 2 y1, y2 = center_y - self.c_size // 2, center_y + self.c_size // 2 imgs = [img[y1:y2, x1:x2] for img in results['imgs']] results['imgs'] = imgs results['img_shape'] = imgs[0].shape[:2] return results @TRANSFORMS.register_module() class VideoFormat(BaseTransform): def transform(self, results): num_clips = results['num_clips'] clip_len = results['clip_len'] imgs = results['imgs'] # [num_clips*clip_len, H, W, C] imgs = np.array(imgs) # [num_clips, clip_len, H, W, C] imgs = imgs.reshape((num_clips, clip_len) + imgs.shape[1:]) # [num_clips, C, clip_len, H, W] imgs = imgs.transpose(0, 4, 1, 2, 3) results['imgs'] = imgs return results @TRANSFORMS.register_module() class VideoPack(BaseTransform): def __init__(self, meta_keys=('img_shape', 'num_clips', 'clip_len')): self.meta_keys = meta_keys def transform(self, results): packed_results = dict() inputs = to_tensor(results['imgs']) data_sample = ActionDataSample().set_gt_labels(results['label']) metainfo = {k: results[k] for k in self.meta_keys if k in results} data_sample.set_metainfo(metainfo) packed_results['inputs'] = inputs packed_results['data_samples'] = data_sample return packed_results ``` 下面，我们提供了一个代码片段(使用标注文件中的 `D32_1gwq35E.mp4 0` )来演示如何使用数据流水线。 ```python import os.path as osp from mmengine.dataset import Compose pipeline_cfg = [ dict(type='VideoInit'), dict(type='VideoSample', clip_len=16, num_clips=1, test_mode=False), dict(type='VideoDecode'), dict(type='VideoResize', r_size=256), dict(type='VideoCrop', c_size=224), dict(type='VideoFormat'), dict(type='VideoPack') ] pipeline = Compose(pipeline_cfg) data_prefix = 'data/kinetics400_tiny/train' results = dict(filename=osp.join(data_prefix, 'D32_1gwq35E.mp4'), label=0) packed_results = pipeline(results) inputs = packed_results['inputs'] data_sample = packed_results['data_samples'] print('shape of the inputs: ', inputs.shape) # 获取输入的信息 print('image_shape: ', data_sample.img_shape) print('num_clips: ', data_sample.num_clips) print('clip_len: ', data_sample.clip_len) # 获取输入的标签 print('label: ', data_sample.gt_labels.item) ``` ``` shape of the inputs: torch.Size([1, 3, 16, 224, 224]) image_shape: (224, 224) num_clips: 1 clip_len: 16 label: tensor([0]) ``` ## 步骤2：构建一个数据集和数据加载器 OpenMMLab中的所有 `Dataset` 类都必须继承自 `mmengine` 中的 `BaseDataset` 类。我们可以通过覆盖 `load_data_list` 方法来定制注释加载过程。此外，我们可以通过覆盖 `get_data_info` 方法，向 `results` 字典添加更多字段，它将作为输入传给 `pipeline` 。有关 `BaseDataset` 类的更多详细信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/advanced_tutorials/basedataset.html) 。 ```python import os.path as osp from mmengine.fileio import list_from_file from mmengine.dataset import BaseDataset from mmaction.registry import DATASETS @DATASETS.register_module() class DatasetZelda(BaseDataset): def __init__(self, ann_file, pipeline, data_root, data_prefix=dict(video=''), test_mode=False, modality='RGB', **kwargs): self.modality = modality super(DatasetZelda, self).__init__(ann_file=ann_file, pipeline=pipeline, data_root=data_root, data_prefix=data_prefix, test_mode=test_mode, **kwargs) def load_data_list(self): data_list = [] fin = list_from_file(self.ann_file) for line in fin: line_split = line.strip().split() filename, label = line_split label = int(label) filename = osp.join(self.data_prefix['video'], filename) data_list.append(dict(filename=filename, label=label)) return data_list def get_data_info(self, idx: int) -> dict: data_info = super().get_data_info(idx) data_info['modality'] = self.modality return data_info ``` 接下来，我们将演示如何使用 dataset 和 dataloader 来索引数据。我们将使用 `Runner.build_dataloader` 方法来构造 dataloader。有关 dataloader 的更多详细信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/tutorials/dataset.html#details-on-dataloader) 。 ```python from mmaction.registry import DATASETS train_pipeline_cfg = [ dict(type='VideoInit'), dict(type='VideoSample', clip_len=16, num_clips=1, test_mode=False), dict(type='VideoDecode'), dict(type='VideoResize', r_size=256), dict(type='VideoCrop', c_size=224), dict(type='VideoFormat'), dict(type='VideoPack') ] val_pipeline_cfg = [ dict(type='VideoInit'), dict(type='VideoSample', clip_len=16, num_clips=5, test_mode=True), dict(type='VideoDecode'), dict(type='VideoResize', r_size=256), dict(type='VideoCrop', c_size=224), dict(type='VideoFormat'), dict(type='VideoPack') ] train_dataset_cfg = dict( type='DatasetZelda', ann_file='kinetics_tiny_train_video.txt', pipeline=train_pipeline_cfg, data_root='data/kinetics400_tiny/', data_prefix=dict(video='train')) val_dataset_cfg = dict( type='DatasetZelda', ann_file='kinetics_tiny_val_video.txt', pipeline=val_pipeline_cfg, data_root='data/kinetics400_tiny/', data_prefix=dict(video='val')) train_dataset = DATASETS.build(train_dataset_cfg) packed_results = train_dataset[0] inputs = packed_results['inputs'] data_sample = packed_results['data_samples'] print('shape of the inputs: ', inputs.shape) # 获取输入的信息 print('image_shape: ', data_sample.img_shape) print('num_clips: ', data_sample.num_clips) print('clip_len: ', data_sample.clip_len) # 获取输入的标签 print('label: ', data_sample.gt_labels.item) from mmengine.runner import Runner BATCH_SIZE = 2 train_dataloader_cfg = dict( batch_size=BATCH_SIZE, num_workers=0, persistent_workers=False, sampler=dict(type='DefaultSampler', shuffle=True), dataset=train_dataset_cfg) val_dataloader_cfg = dict( batch_size=BATCH_SIZE, num_workers=0, persistent_workers=False, sampler=dict(type='DefaultSampler', shuffle=False), dataset=val_dataset_cfg) train_data_loader = Runner.build_dataloader(dataloader=train_dataloader_cfg) val_data_loader = Runner.build_dataloader(dataloader=val_dataloader_cfg) batched_packed_results = next(iter(train_data_loader)) batched_inputs = batched_packed_results['inputs'] batched_data_sample = batched_packed_results['data_samples'] assert len(batched_inputs) == BATCH_SIZE assert len(batched_data_sample) == BATCH_SIZE ``` 终端输出应该与[步骤1：构建一个数据流水线](#步骤1：构建一个数据流水线)中的输出相同。 ## 步骤3：构建一个识别器 接下来，我们将构建 `recognizer`，它主要由三部分组成：用于批处理和规范化数据的 `data preprocessor`，用于特征提取的 `backbone` 和用于分类的 `cls_head` 。 `data_preprocessor` 的实现如下: ```python import torch from mmengine.model import BaseDataPreprocessor, stack_batch from mmaction.registry import MODELS @MODELS.register_module() class DataPreprocessorZelda(BaseDataPreprocessor): def __init__(self, mean, std): super().__init__() self.register_buffer( 'mean', torch.tensor(mean, dtype=torch.float32).view(-1, 1, 1, 1), False) self.register_buffer( 'std', torch.tensor(std, dtype=torch.float32).view(-1, 1, 1, 1), False) def forward(self, data, training=False): data = self.cast_data(data) inputs = data['inputs'] batch_inputs = stack_batch(inputs) # 批处理 batch_inputs = (batch_inputs - self.mean) / self.std # 归一化 data['inputs'] = batch_inputs return data ``` 以下是 data_preprocessor 的用法：将从[步骤2：构建一个数据集和数据加载器](#步骤2：构建一个数据集和数据加载器)中获得的 `batched_packed_results` 提供给 `data_preprocessor` 进行批处理和归一化。 ```python from mmaction.registry import MODELS data_preprocessor_cfg = dict( type='DataPreprocessorZelda', mean=[123.675, 116.28, 103.53], std=[58.395, 57.12, 57.375]) data_preprocessor = MODELS.build(data_preprocessor_cfg) preprocessed_inputs = data_preprocessor(batched_packed_results) print(preprocessed_inputs['inputs'].shape) ``` ``` torch.Size([2, 1, 3, 16, 224, 224]) ``` `backbone`、`cls_head` 和 `recognizer` 的实现如下: ```python import torch import torch.nn as nn import torch.nn.functional as F from mmengine.model import BaseModel, BaseModule, Sequential from mmengine.structures import LabelData from mmaction.registry import MODELS @MODELS.register_module() class BackBoneZelda(BaseModule): def __init__(self, init_cfg=None): if init_cfg is None: init_cfg = [dict(type='Kaiming', layer='Conv3d', mode='fan_out', nonlinearity="relu"), dict(type='Constant', layer='BatchNorm3d', val=1, bias=0)] super(BackBoneZelda, self).__init__(init_cfg=init_cfg) self.conv1 = Sequential(nn.Conv3d(3, 64, kernel_size=(3, 7, 7), stride=(1, 2, 2), padding=(1, 3, 3)), nn.BatchNorm3d(64), nn.ReLU()) self.maxpool = nn.MaxPool3d(kernel_size=(1, 3, 3), stride=(1, 2, 2), padding=(0, 1, 1)) self.conv = Sequential(nn.Conv3d(64, 128, kernel_size=3, stride=2, padding=1), nn.BatchNorm3d(128), nn.ReLU()) def forward(self, imgs): # imgs: [batch_size*num_views, 3, T, H, W] # features: [batch_size*num_views, 128, T/2, H//8, W//8] features = self.conv(self.maxpool(self.conv1(imgs))) return features @MODELS.register_module() class ClsHeadZelda(BaseModule): def __init__(self, num_classes, in_channels, dropout=0.5, average_clips='prob', init_cfg=None): if init_cfg is None: init_cfg = dict(type='Normal', layer='Linear', std=0.01) super(ClsHeadZelda, self).__init__(init_cfg=init_cfg) self.num_classes = num_classes self.in_channels = in_channels self.average_clips = average_clips if dropout != 0: self.dropout = nn.Dropout(dropout) else: self.dropout = None self.fc = nn.Linear(self.in_channels, self.num_classes) self.pool = nn.AdaptiveAvgPool3d(1) self.loss_fn = nn.CrossEntropyLoss() def forward(self, x): N, C, T, H, W = x.shape x = self.pool(x) x = x.view(N, C) assert x.shape[1] == self.in_channels if self.dropout is not None: x = self.dropout(x) cls_scores = self.fc(x) return cls_scores def loss(self, feats, data_samples): cls_scores = self(feats) labels = torch.stack([x.gt_labels.item for x in data_samples]) labels = labels.squeeze() if labels.shape == torch.Size([]): labels = labels.unsqueeze(0) loss_cls = self.loss_fn(cls_scores, labels) return dict(loss_cls=loss_cls) def predict(self, feats, data_samples): cls_scores = self(feats) num_views = cls_scores.shape[0] // len(data_samples) # assert num_views == data_samples[0].num_clips cls_scores = self.average_clip(cls_scores, num_views) for ds, sc in zip(data_samples, cls_scores): pred = LabelData(item=sc) ds.pred_scores = pred return data_samples def average_clip(self, cls_scores, num_views): if self.average_clips not in ['score', 'prob', None]: raise ValueError(f'{self.average_clips} is not supported. ' f'Currently supported ones are ' f'["score", "prob", None]') total_views = cls_scores.shape[0] cls_scores = cls_scores.view(total_views // num_views, num_views, -1) if self.average_clips is None: return cls_scores elif self.average_clips == 'prob': cls_scores = F.softmax(cls_scores, dim=2).mean(dim=1) elif self.average_clips == 'score': cls_scores = cls_scores.mean(dim=1) return cls_scores @MODELS.register_module() class RecognizerZelda(BaseModel): def __init__(self, backbone, cls_head, data_preprocessor): super().__init__(data_preprocessor=data_preprocessor) self.backbone = MODELS.build(backbone) self.cls_head = MODELS.build(cls_head) def extract_feat(self, inputs): inputs = inputs.view((-1, ) + inputs.shape[2:]) return self.backbone(inputs) def loss(self, inputs, data_samples): feats = self.extract_feat(inputs) loss = self.cls_head.loss(feats, data_samples) return loss def predict(self, inputs, data_samples): feats = self.extract_feat(inputs) predictions = self.cls_head.predict(feats, data_samples) return predictions def forward(self, inputs, data_samples=None, mode='tensor'): if mode == 'tensor': return self.extract_feat(inputs) elif mode == 'loss': return self.loss(inputs, data_samples) elif mode == 'predict': return self.predict(inputs, data_samples) else: raise RuntimeError(f'Invalid mode: {mode}') ``` `init_cfg` 用于模型权重初始化。有关模型权重初始化的更多信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/advanced_tutorials/initialize.html) 。上述模块的用法如下: ```python import torch import copy from mmaction.registry import MODELS model_cfg = dict( type='RecognizerZelda', backbone=dict(type='BackBoneZelda'), cls_head=dict( type='ClsHeadZelda', num_classes=2, in_channels=128, average_clips='prob'), data_preprocessor = dict( type='DataPreprocessorZelda', mean=[123.675, 116.28, 103.53], std=[58.395, 57.12, 57.375])) model = MODELS.build(model_cfg) # 训练 model.train() model.init_weights() data_batch_train = copy.deepcopy(batched_packed_results) data = model.data_preprocessor(data_batch_train, training=True) loss = model(**data, mode='loss') print('loss dict: ', loss) # 验证 with torch.no_grad(): model.eval() data_batch_test = copy.deepcopy(batched_packed_results) data = model.data_preprocessor(data_batch_test, training=False) predictions = model(**data, mode='predict') print('Label of Sample[0]', predictions[0].gt_labels.item) print('Scores of Sample[0]', predictions[0].pred_scores.item) ``` ```shell 04/03 23:28:01 - mmengine - INFO - backbone.conv1.0.weight - torch.Size([64, 3, 3, 7, 7]): KaimingInit: a=0, mode=fan_out, nonlinearity=relu, distribution =normal, bias=0 04/03 23:28:01 - mmengine - INFO - backbone.conv1.0.bias - torch.Size([64]): KaimingInit: a=0, mode=fan_out, nonlinearity=relu, distribution =normal, bias=0 04/03 23:28:01 - mmengine - INFO - backbone.conv1.1.weight - torch.Size([64]): The value is the same before and after calling `init_weights` of RecognizerZelda 04/03 23:28:01 - mmengine - INFO - backbone.conv1.1.bias - torch.Size([64]): The value is the same before and after calling `init_weights` of RecognizerZelda 04/03 23:28:01 - mmengine - INFO - backbone.conv.0.weight - torch.Size([128, 64, 3, 3, 3]): KaimingInit: a=0, mode=fan_out, nonlinearity=relu, distribution =normal, bias=0 04/03 23:28:01 - mmengine - INFO - backbone.conv.0.bias - torch.Size([128]): KaimingInit: a=0, mode=fan_out, nonlinearity=relu, distribution =normal, bias=0 04/03 23:28:01 - mmengine - INFO - backbone.conv.1.weight - torch.Size([128]): The value is the same before and after calling `init_weights` of RecognizerZelda 04/03 23:28:01 - mmengine - INFO - backbone.conv.1.bias - torch.Size([128]): The value is the same before and after calling `init_weights` of RecognizerZelda 04/03 23:28:01 - mmengine - INFO - cls_head.fc.weight - torch.Size([2, 128]): NormalInit: mean=0, std=0.01, bias=0 04/03 23:28:01 - mmengine - INFO - cls_head.fc.bias - torch.Size([2]): NormalInit: mean=0, std=0.01, bias=0 loss dict: {'loss_cls': tensor(0.6853, grad_fn=)} Label of Sample[0] tensor([0]) Scores of Sample[0] tensor([0.5240, 0.4760]) ``` ## 步骤4：构建一个评估指标 请注意，`OpenMMLab` 中的所有 `Metric` 类都必须继承自 `mmengine` 中的 `BaseMetric` 类，并实现抽象方法 `process` 和`compute_metrics`。有关评估的更多信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/tutorials/evaluation.html) 。 ```python import copy from collections import OrderedDict from mmengine.evaluator import BaseMetric from mmaction.evaluation import top_k_accuracy from mmaction.registry import METRICS @METRICS.register_module() class AccuracyMetric(BaseMetric): def __init__(self, topk=(1, 5), collect_device='cpu', prefix='acc'): super().__init__(collect_device=collect_device, prefix=prefix) self.topk = topk def process(self, data_batch, data_samples): data_samples = copy.deepcopy(data_samples) for data_sample in data_samples: result = dict() scores = data_sample['pred_scores']['item'].cpu().numpy() label = data_sample['gt_labels']['item'].item() result['scores'] = scores result['label'] = label self.results.append(result) def compute_metrics(self, results: list) -> dict: eval_results = OrderedDict() labels = [res['label'] for res in results] scores = [res['scores'] for res in results] topk_acc = top_k_accuracy(scores, labels, self.topk) for k, acc in zip(self.topk, topk_acc): eval_results[f'topk{k}'] = acc return eval_results ``` ```python from mmaction.registry import METRICS metric_cfg = dict(type='AccuracyMetric', topk=(1, 5)) metric = METRICS.build(metric_cfg) data_samples = [d.to_dict() for d in predictions] metric.process(batched_packed_results, data_samples) acc = metric.compute_metrics(metric.results) print(acc) ``` ```shell OrderedDict([('topk1', 0.5), ('topk5', 1.0)]) ``` ## 步骤5：使用本地 PyTorch 训练和测试 ```python import torch.optim as optim from mmengine import track_iter_progress device = 'cuda' # or 'cpu' max_epochs = 10 optimizer = optim.Adam(model.parameters(), lr=0.01) for epoch in range(max_epochs): model.train() losses = [] for data_batch in track_iter_progress(train_data_loader): data = model.data_preprocessor(data_batch, training=True) loss_dict = model(**data, mode='loss') loss = loss_dict['loss_cls'] optimizer.zero_grad() loss.backward() optimizer.step() losses.append(loss.item()) print(f'Epoch[{epoch}]: loss ', sum(losses) / len(train_data_loader)) with torch.no_grad(): model.eval() for data_batch in track_iter_progress(val_data_loader): data = model.data_preprocessor(data_batch, training=False) predictions = model(**data, mode='predict') data_samples = [d.to_dict() for d in predictions] metric.process(data_batch, data_samples) acc = metric.acc = metric.compute_metrics(metric.results) for name, topk in acc.items(): print(f'{name}: ', topk) ``` ## 步骤6：使用 MMEngine 训练和测试（推荐） 关于训练和测试的更多细节，你可以参考[ MMAction2 教程](https://mmaction2.readthedocs.io/en/latest/user_guides/train_test.html) 。有关 `Runner` 的更多信息，请参阅[ MMEngine 教程](https://mmengine.readthedocs.io/en/latest/tutorials/runner.html) 。 ```python from mmengine.runner import Runner train_cfg = dict(type='EpochBasedTrainLoop', max_epochs=10, val_interval=1) val_cfg = dict(type='ValLoop') optim_wrapper = dict(optimizer=dict(type='Adam', lr=0.01)) runner = Runner(model=model_cfg, work_dir='./work_dirs/guide', train_dataloader=train_dataloader_cfg, train_cfg=train_cfg, val_dataloader=val_dataloader_cfg, val_cfg=val_cfg, optim_wrapper=optim_wrapper, val_evaluator=[metric_cfg], default_scope='mmaction') runner.train() ```