Migration from MMClassification 0.x

We introduce some modifications in MMClassification 1.x, and some of them are BC-breading. To migrate your projects from MMClassification 0.x smoothly, please read this tutorial.

New dependencies

MMClassification 1.x depends on some new packages, you can prepare a new clean environment and install again according to the install tutorial. Or install the below packages manually.

1. MMEngine: MMEngine is the core the OpenMMLab 2.0 architecture, and we splited many compentents unrelated to computer vision from MMCV to MMEngine.

2. MMCV: The computer vision package of OpenMMLab. This is not a new dependency, but you need to upgrade it to above 2.0.0rc1 version.

3. rich: A terminal formatting package, and we use it to beautify some outputs in the terminal.

Configuration files

In MMClassification 1.x, we refactored the structure of configuration files, and the original files are not usable.

In this section, we will introduce all changes of the configuration files. And we assume you already have ideas of the config files.

Model settings

No changes in model.backbone, model.neck and model.head fields.

Changes in model.train_cfg:

• BatchMixup is renamed to Mixup.

• BatchCutMix is renamed to CutMix.

• BatchResizeMix is renamed to ResizeMix.

• The prob argument is removed from all augments settings, and you can use the probs field in train_cfg to specify probabilities of every augemnts. If no probs field, randomly choose one by the same probability.

Original	model = dict( ... train_cfg=dict(augments=[ dict(type='BatchMixup', alpha=0.8, num_classes=1000, prob=0.5), dict(type='BatchCutMix', alpha=1.0, num_classes=1000, prob=0.5) ] )
New	model = dict( ... train_cfg=dict(augments=[ dict(type='Mixup', alpha=0.8), dict(type='CutMix', alpha=1.0)] )

Data settings

Changes in data:

• The original data field is splited to train_dataloader, val_dataloader and test_dataloader. This allows us to configure them in fine-grained. For example, you can specify different sampler and batch size during training and test.

• The samples_per_gpu is renamed to batch_size.

• The workers_per_gpu is renamed to num_workers.

Original	data = dict( samples_per_gpu=32, workers_per_gpu=2, train=dict(...), val=dict(...), test=dict(...), )
New	train_dataloader = dict( batch_size=32, num_workers=2, dataset=dict(...), sampler=dict(type='DefaultSampler', shuffle=True) # necessary ) val_dataloader = dict( batch_size=32, num_workers=2, dataset=dict(...), sampler=dict(type='DefaultSampler', shuffle=False) # necessary ) test_dataloader = val_dataloader

Changes in pipeline:

• The original formatting transforms ToTensor, ImageToTensor and Collect are combined as PackClsInputs.

• We don’t recommend to do Normalize in the dataset pipeline. Please remove it from pipelines and set it in the data_preprocessor field.

• The argument flip_prob in RandomFlip is renamed to flip.

• The argument size in RandomCrop is renamed to crop_size.

• The argument size in RandomResizedCrop is renamed to scale.

• The argument size in Resize is renamed to scale. And Resize won’t support size like (256, -1), please use ResizeEdge to replace it.

• The argument policies in AutoAugment and RandAugment supports using string to specify preset policies. AutoAugment supports “imagenet” and RandAugment supports “timm_increasing”.

• RandomResizedCrop and CenterCrop won’t supports efficientnet_style, and please use EfficientNetRandomCrop and EfficientNetCenterCrop to replace them.

Note

We move some work of data transforms to the data preprocessor, like normalization, see the documentation for more details.

Original

img_norm_cfg = dict( mean=[123.675, 116.28, 103.53], std=[58.395, 57.12, 57.375], to_rgb=True) train_pipeline = [ dict(type='LoadImageFromFile'), dict(type='RandomResizedCrop', size=224), dict(type='RandomFlip', flip_prob=0.5, direction='horizontal'), dict(type='Normalize', **img_norm_cfg), dict(type='ImageToTensor', keys=['img']), dict(type='ToTensor', keys=['gt_label']), dict(type='Collect', keys=['img', 'gt_label']) ]

New

data_preprocessor = dict( mean=[123.675, 116.28, 103.53], std=[58.395, 57.12, 57.375], to_rgb=True) train_pipeline = [ dict(type='LoadImageFromFile'), dict(type='RandomResizedCrop', scale=224), dict(type='RandomFlip', prob=0.5, direction='horizontal'), dict(type='PackClsInputs'), ]

Changes in evaluation:

• The evaluation field is splited to val_evaluator and test_evaluator. And it won’t supports interval and save_best arguments. The interval is moved to train_cfg.val_interval, see the schedule settings and the save_best is moved to default_hooks.checkpoint.save_best, see the runtime settings.

• The ‘accuracy’ metric is renamed to Accuracy.

• The ‘precision’, ‘recall’, ‘f1-score’ and ‘support’ are combined as SingleLabelMetric, and use items argument to specify to calculate which metric.

• The ‘mAP’ is renamed to AveragePrecision.

• The ‘CP’, ‘CR’, ‘CF1’, ‘OP’, ‘OR’, ‘OF1’ are combined as MultiLabelMetric, and use items and average arguments to specify to calculate which metric.

Original	evaluation = dict( interval=1, metric='accuracy', metric_options=dict(topk=(1, 5)) )
New	val_evaluator = dict(type='Accuracy', topk=(1, 5)) test_evaluator = val_evaluator
Original	evaluation = dict( interval=1, metric=['mAP', 'CP', 'OP', 'CR', 'OR', 'CF1', 'OF1'], metric_options=dict(thr=0.5), )
New	val_evaluator = [ dict(type='AveragePrecision'), dict(type='MultiLabelMetric', items=['precision', 'recall', 'f1-score'], average='both', thr=0.5), ] test_evaluator = val_evaluator

Schedule settings

Changes in optimizer and optimizer_config:

• Now we use optim_wrapper field to specify all configuration about the optimization process. And the optimizer is a sub field of optim_wrapper now.

• paramwise_cfg is also a sub field of optim_wrapper, instead of optimizer.

• optimizer_config is removed now, and all configurations of it are moved to optim_wrapper.

• grad_clip is renamed to clip_grad.

Original	optimizer = dict( type='AdamW', lr=0.0015, weight_decay=0.3, paramwise_cfg = dict( norm_decay_mult=0.0, bias_decay_mult=0.0, )) optimizer_config = dict(grad_clip=dict(max_norm=1.0))
New	optim_wrapper = dict( optimizer=dict(type='AdamW', lr=0.0015, weight_decay=0.3), paramwise_cfg = dict( norm_decay_mult=0.0, bias_decay_mult=0.0, ), clip_grad=dict(max_norm=1.0), )

Changes in lr_config:

• The lr_config field is removed and we use new param_scheduler to replace it.

• The warmup related arguments are removed, since we use schedulers combination to implement this functionality.

The new schedulers combination mechanism is very flexible, and you can use it to design many kinds of learning rate / momentum curves. See the tutorial for more details.

Original	lr_config = dict( policy='CosineAnnealing', min_lr=0, warmup='linear', warmup_iters=5, warmup_ratio=0.01, warmup_by_epoch=True)
New	param_scheduler = [ # warmup dict( type='LinearLR', start_factor=0.01, by_epoch=True, end=5, # Update the learning rate after every iters. convert_to_iter_based=True), # main learning rate scheduler dict(type='CosineAnnealingLR', by_epoch=True, begin=5), ]

Changes in runner:

Most configuration in the original runner field is moved to train_cfg, val_cfg and test_cfg, which configure the loop in training, validation and test.

Original	runner = dict(type='EpochBasedRunner', max_epochs=100)
New	# The `val_interval` is the original `evaluation.interval`. train_cfg = dict(by_epoch=True, max_epochs=100, val_interval=1) val_cfg = dict() # Use the default validation loop. test_cfg = dict() # Use the default test loop.

In fact, in OpenMMLab 2.0, we introduced Loop to control the behaviors in training, validation and test. And the functionalities of Runner are also changed. You can find more details in the MMEngine tutorials.

Runtime settings

Changes in checkpoint_config and log_config:

The checkpoint_config are moved to default_hooks.checkpoint and the log_config are moved to default_hooks.logger. And we move many hooks settings from the script code to the default_hooks field in the runtime configuration.

default_hooks = dict(
    # record the time of every iterations.
    timer=dict(type='IterTimerHook'),

    # print log every 100 iterations.
    logger=dict(type='LoggerHook', interval=100),

    # enable the parameter scheduler.
    param_scheduler=dict(type='ParamSchedulerHook'),

    # save checkpoint per epoch, and automatically save the best checkpoint.
    checkpoint=dict(type='CheckpointHook', interval=1, save_best='auto'),

    # set sampler seed in distributed evrionment.
    sampler_seed=dict(type='DistSamplerSeedHook'),

    # validation results visualization, set True to enable it.
    visualization=dict(type='VisualizationHook', enable=False),
)

In addition, we splited the original logger to logger and visualizer. The logger is used to record information and the visualizer is used to show the logger in different backends, like terminal, TensorBoard and Wandb.

Original	log_config = dict( interval=100, hooks=[ dict(type='TextLoggerHook'), dict(type='TensorboardLoggerHook'), ])
New	default_hooks = dict( ... logger=dict(type='LoggerHook', interval=100), ) visualizer = dict( type='ClsVisualizer', vis_backends=[dict(type='LocalVisBackend'), dict(type='TensorboardVisBackend')], )

Changes in load_from and resume_from:

• The resume_from is removed. And we use resume and load_from to replace it.

  • If resume=True and load_from is not None, resume training from the checkpoint in load_from.

  • If resume=True and load_from is None, try to resume from the latest checkpoint in the work directory.

  • If resume=False and load_from is not None, only load the checkpoint, not resume training.

  • If resume=False and load_from is None, do not load nor resume.

Changes in dist_params: The dist_params field is a sub field of env_cfg now. And there are some new configurations in the env_cfg.

env_cfg = dict(
    # whether to enable cudnn benchmark
    cudnn_benchmark=False,

    # set multi process parameters
    mp_cfg=dict(mp_start_method='fork', opencv_num_threads=0),

    # set distributed parameters
    dist_cfg=dict(backend='nccl'),
)

Changes in workflow: workflow related functionalities are removed.

New field visualizer: The visualizer is a new design in OpenMMLab 2.0 architecture. We use a visualizer instance in the runner to handle results & log visualization and save to different backends. See the MMEngine tutorial for more details.

visualizer = dict(
    type='ClsVisualizer',
    vis_backends=[
        dict(type='LocalVisBackend'),
        # Uncomment the below line to save the log and visualization results to TensorBoard.
        # dict(type='TensorboardVisBackend')
    ]
)

New field default_scope: The start point to search module for all registries. The default_scope in MMClassification is mmcls. See the registry tutorial for more details.

Packages

mmcls.apis

The documentation can be found here.

Function	Changes
init_model	No changes
inference_model	No changes. But we recommend to use mmcls.ImageClassificationInferencer instead.
train_model	Removed, use runner.train to train.
multi_gpu_test	Removed, use runner.test to test.
single_gpu_test	Removed, use runner.test to test.
show_result_pyplot	Removed, use mmcls.ImageClassificationInferencer to inference model and show the result.
set_random_seed	Removed, use mmengine.runner.set_random_seed.
init_random_seed	Removed, use mmengine.dist.sync_random_seed.

mmcls.core

The mmcls.core package is renamed to mmcls.engine.

Sub package	Changes
evaluation	Removed, use the metrics in mmcls.evaluation.
hook	Moved to mmcls.engine.hooks
optimizers	Moved to mmcls.engine.optimizers
utils	Removed, the distributed environment related functions can be found in the mmengine.dist package.
visualization	Removed, the related functionalities are implemented in mmengine.visualization.Visualizer.

The MMClsWandbHook in hooks package is waiting for implementation.

The CosineAnnealingCooldownLrUpdaterHook in hooks package is removed, and we support this functionality by the combination of parameter schedulers, see the tutorial.

mmcls.datasets

The documentation can be found here.

Dataset class	Changes
CustomDataset	Add data_root argument as the common prefix of data_prefix and ann_file.
ImageNet	Same as CustomDataset.
ImageNet21k	Same as CustomDataset.
CIFAR10 & CIFAR100	The test_mode argument is a required argument now.
MNIST & FashionMNIST	The test_mode argument is a required argument now.
VOC	Requires data_root, image_set_path and test_mode now.
CUB	Requires data_root and test_mode now.

The mmcls.datasets.pipelines is renamed to mmcls.datasets.transforms.

Transform class	Changes
LoadImageFromFile	Removed, use mmcv.transforms.LoadImageFromFile.
RandomFlip	Removed, use mmcv.transforms.RandomFlip. The argument flip_prob is renamed to prob.
RandomCrop	The argument size is renamed to crop_size.
RandomResizedCrop	The argument size is renamed to scale. The argument scale is renamed to crop_ratio_range. Won’t support efficientnet_style, use EfficientNetRandomCrop.
CenterCrop	Removed, use mmcv.transforms.CenterCrop. Won’t support efficientnet_style, use EfficientNetCenterCrop.
Resize	Removed, use mmcv.transforms.Resize. The argument size is renamed to scale. Won’t support size like (256, -1), use ResizeEdge.
AutoAugment & RandomAugment	The argument policies supports using string to specify preset policies.
Compose	Removed, use mmcv.transforms.Compose.

mmcls.models

The documentation can be found here. The interface of all backbones, necks and losses didn’t change.

Changes in ImageClassifier:

Method of classifiers	Changes
extract_feat	No changes
forward	Now only accepts three arguments: inputs, data_samples and mode. See the documentation for more details.
forward_train	Replaced by loss.
simple_test	Replaced by predict.
train_step	The optimizer argument is replaced by optim_wrapper and it accepts OptimWrapper.
val_step	The original val_step is the same as train_step, now it calls predict.
test_step	New method, and it’s the same as val_step.

Changes in heads:

Method of heads	Changes
pre_logits	No changes
forward_train	Replaced by loss.
simple_test	Replaced by predict.
loss	It accepts data_samples instead of gt_labels to calculate loss. The data_samples is a list of ClsDataSample.
forward	New method, and it returns the output of the classification head without any post-processs like softmax or sigmoid.

mmcls.utils

Function	Changes
collect_env	No changes
get_root_logger	Removed, use mmengine.logging.MMLogger.get_current_instance
load_json_log	The output format changed.
setup_multi_processes	Removed, use mmengine.utils.dl_utils.set_multi_processing.
wrap_non_distributed_model	Removed, we auto wrap the model in the runner.
wrap_distributed_model	Removed, we auto wrap the model in the runner.
auto_select_device	Removed, we auto select the device in the runner.

Other changes

• We moved the definition of all registries in different packages to the mmcls.registry package.