# Tutorial 1: Learn about Configs¶

We incorporate modular and inheritance design into our config system, which is convenient to conduct various experiments. If you wish to inspect the config file, you may run python tools/misc/print_config.py /PATH/TO/CONFIG to see the complete config. The detection part of mmfewshot is built upon the mmdet, thus it is highly recommended learning the basic of mmdet.

## Modify a config through script arguments¶

When submitting jobs using “tools/train.py” or “tools/test.py”, you may specify --cfg-options to in-place modify the config.

• Update config keys of dict chains.

The config options can be specified following the order of the dict keys in the original config. For example, --cfg-options model.backbone.norm_eval=False changes the all BN modules in model backbones to train mode.

• Update keys inside a list of configs.

Some config dicts are composed as a list in your config. For example, the training pipeline data.train.pipeline is normally a list e.g. [dict(type='LoadImageFromFile'), ...]. If you want to change 'LoadImageFromFile' to 'LoadImageFromWebcam' in the pipeline, you may specify --cfg-options data.train.pipeline.0.type=LoadImageFromWebcam.

• Update values of list/tuples.

If the value to be updated is a list or a tuple. For example, the config file normally sets workflow=[('train', 1)]. If you want to change this key, you may specify --cfg-options workflow="[(train,1),(val,1)]". Note that the quotation mark ” is necessary to support list/tuple data types, and that NO white space is allowed inside the quotation marks in the specified value.

## Config File Naming Convention¶

We follow the below style to name config files. Contributors are advised to follow the same style.

{model}_[model setting]_{backbone}_{neck}_[norm setting]_[misc]_[gpu x batch_per_gpu]_{dataset}_{data setting}


{xxx} is required field and [yyy] is optional.

• {model}: model type like faster_rcnn, mask_rcnn, etc.

• [model setting]: specific setting for some model, like contrastive-loss for fsce, etc.

• {backbone}: backbone type like r50 (ResNet-50), x101 (ResNeXt-101).

• {neck}: neck type like fpn, c4.

• [norm_setting]: bn (Batch Normalization) is used unless specified, other norm layer type could be gn (Group Normalization), syncbn (Synchronized Batch Normalization). gn-head/gn-neck indicates GN is applied in head/neck only, while gn-all means GN is applied in the entire model, e.g. backbone, neck, head.

• [misc]: miscellaneous setting/plugins of model, e.g. dconv, gcb, attention, albu, mstrain.

• [gpu x batch_per_gpu]: GPUs and samples per GPU, 8xb2 is used by default.

• {dataset}: dataset like coco, voc-split1, voc-split2 and voc-split3.

• {data setting}: like base-training or 1shot-fine-tuning.

## An Example of TFA¶

To help the users have a basic idea of a complete config and the modules in a modern classification system, we make brief comments on the config of TFA in coco 10 shot fine-tuning setting as the following. For more detailed usage and the corresponding alternative for each module, please refer to the API documentation.

train_pipeline = [  # Training pipeline
# First pipeline to load images from file path
# Second pipeline to load annotations for current image
# Augmentation pipeline that resize the images and their annotations
dict(type='Resize',
# The multiple scales of image
img_scale=[(1333, 640), (1333, 672), (1333, 704), (1333, 736),
(1333, 768), (1333, 800)],
# whether to keep the ratio between height and width
keep_ratio=True,
# the scales will be sampled from img_scale
multiscale_mode='value'),
# RandomFlip config, flip_ratio: the ratio or probability to flip
dict(type='RandomFlip', flip_ratio=0.5),
# Image normalization config to normalize the input images
dict(type='Normalize',
# Mean values used to in pre-trained backbone models
mean=[103.53, 116.28, 123.675],
# Standard variance used to in pre-trained backbone models
std=[1.0, 1.0, 1.0],
# The channel orders of image used in pre-trained backbone models
to_rgb=False),
# Padding config, size_divisor: the number the padded images should be divisible
# Default format bundle to gather data in the pipeline
dict(type='DefaultFormatBundle'),
# Pipeline that decides which keys in the data should be passed to the detector
dict(type='Collect', keys=['img', 'gt_bboxes', 'gt_labels'])
]
test_pipeline = [  # test pipeline
# First pipeline to load images from file path
# An encapsulation that encapsulates the testing augmentations
dict(type='MultiScaleFlipAug',
# Decides the largest scale for testing, used for the Resize pipeline
img_scale=(1333, 800),
flip=False,  # Whether to flip images during testing
transforms=[
# Use resize augmentation
dict(type='Resize', keep_ratio=True),
# Augmentation pipeline that flip the images and their annotations
dict(type='RandomFlip'),
# Augmentation pipeline that normalize the input images
dict(type='Normalize',
# Mean values used in pre-trained backbone models
mean=[103.53, 116.28, 123.675],
# Standard variance used in pre-trained backbone models
std=[1.0, 1.0, 1.0],
# The channel orders of image used in pre-trained backbone models
to_rgb=False),
# Padding config, size_divisor: the number the padded images should be divisible
# Default format bundle to gather data in the pipeline
dict(type='ImageToTensor', keys=['img']),
# Pipeline that decides which keys in the data should be passed to the detector
dict(type='Collect', keys=['img'])
])
]
data = dict(
# Batch size of a single GPU
samples_per_gpu=2,
# Worker to pre-fetch data for each single GPU
workers_per_gpu=2,
train=dict(  # Train dataset config
save_dataset=False,  # whether to save data_information into json file
# the pre-defined few shot setting are saved in FewShotCocoDefaultDataset
type='FewShotCocoDefaultDataset',
ann_cfg=[dict(method='TFA', setting='10SHOT')],  # pre-defined few shot setting
img_prefix='data/coco/',  # prefix of images
num_novel_shots=10,  # the max number of instances for novel classes
num_base_shots=10,  # the max number of instances for base classes
pipeline=train_pipeline,  # training pipeline
classes='ALL_CLASSES',  # pre-defined classes split saved in dataset
# whether to split the annotation (each image only contains one instance)
instance_wise=False),
val=dict(  # Validation dataset config
type='FewShotCocoDataset',  # type of dataset
ann_cfg=[dict(type='ann_file',  # type of ann_file
# path to ann_file
ann_file='data/few_shot_ann/coco/annotations/val.json')],
# prefix of image
img_prefix='data/coco/',
pipeline=test_pipeline,  # testing pipeline
classes='ALL_CLASSES'),
test=dict(  # Testing dataset config
type='FewShotCocoDataset',  # type of dataset
ann_cfg=[dict(type='ann_file',  # type of ann_file
# path to ann_file
ann_file='data/few_shot_ann/coco/annotations/val.json')],
# prefix of image
img_prefix='data/coco/',
pipeline=test_pipeline,  # testing pipeline
test_mode=True,  # indicate in test mode
classes='ALL_CLASSES'))  # pre-defined classes split saved in dataset
# The config to build the evaluation hook, refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/evaluation/eval_hooks.py#L7
# for more details.
evaluation = dict(
interval=80000,  # Evaluation interval
metric='bbox',  # Metrics used during evaluation
classwise=True,  # whether to show result of each class
# eval results in pre-defined split of classes
class_splits=['BASE_CLASSES', 'NOVEL_CLASSES'])
# Config used to build optimizer, support all the optimizers
# in PyTorch whose arguments are also the same as those in PyTorch
optimizer = dict(type='SGD', lr=0.001, momentum=0.9, weight_decay=0.0001)
# Config used to build the optimizer hook, refer to
# https://github.com/open-mmlab/mmcv/blob/master/mmcv/runner/hooks/optimizer.py#L8
# for implementation details. Most of the methods do not use gradient clip.
# Learning rate scheduler config used to register LrUpdater hook
lr_config = dict(
# The policy of scheduler, also support CosineAnnealing, Cyclic, etc.
# Refer to details of supported LrUpdater from
# https://github.com/open-mmlab/mmcv/blob/master/mmcv/runner/hooks/lr_updater.py#L9.
policy='step',
# The warmup policy, also support exp and constant.
warmup='linear',
# The number of iterations for warmup
warmup_iters=10,
# The ratio of the starting learning rate used for warmup
warmup_ratio=0.001,
# Steps to decay the learning rate
step=[144000])
# Type of runner to use (i.e. IterBasedRunner or EpochBasedRunner)
runner = dict(type='IterBasedRunner', max_iters=160000)
model = dict(  # The config of backbone
type='TFA',  # The name of detector
backbone=dict(
type='ResNet',  # The name of detector
# The depth of backbone, usually it is 50 or 101 for ResNet and ResNext backbones.
depth=101,
num_stages=4,  # Number of stages of the backbone.
# The index of output feature maps produced in each stages
out_indices=(0, 1, 2, 3),
# The weights from stages 1 to 4 are frozen
frozen_stages=4,
# The config of normalization layers.
# Whether to freeze the statistics in BN
norm_eval=True,
# The style of backbone, 'pytorch' means that stride 2 layers are in 3x3 conv,
# 'caffe' means stride 2 layers are in 1x1 convs.
style='caffe'),
neck=dict(
# The neck of detector is FPN. For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/necks/fpn.py#L10
type='FPN',
# The input channels, this is consistent with the output channels of backbone
in_channels=[256, 512, 1024, 2048],
# The output channels of each level of the pyramid feature map
out_channels=256,
# The number of output scales
num_outs=5,
# the initialization of specific layer. For more details, please refer to
init_cfg=[
# initialize lateral_convs layer with Caffe2Xavier
dict(type='Caffe2Xavier',
override=dict(type='Caffe2Xavier', name='lateral_convs')),
# initialize fpn_convs layer with Caffe2Xavier
dict(type='Caffe2Xavier',
override=dict(type='Caffe2Xavier', name='fpn_convs'))
]),
# The input channels of each input feature map,
# this is consistent with the output channels of neck
in_channels=256,
# Feature channels of convolutional layers in the head.
feat_channels=256,
anchor_generator=dict(  # The config of anchor generator
# Most of methods use AnchorGenerator, For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/anchor/anchor_generator.py#L10
type='AnchorGenerator',
# Basic scale of the anchor, the area of the anchor in one position
# of a feature map will be scale * base_sizes
scales=[8],
# The ratio between height and width.
ratios=[0.5, 1.0, 2.0],
# The strides of the anchor generator. This is consistent with the FPN
# feature strides. The strides will be taken as base_sizes if base_sizes is not set.
strides=[4, 8, 16, 32, 64]),
bbox_coder=dict(  # Config of box coder to encode and decode the boxes during training and testing
# Type of box coder. 'DeltaXYWHBBoxCoder' is applied for most of methods. For more details refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/coder/delta_xywh_bbox_coder.py#L9
type='DeltaXYWHBBoxCoder',
# The target means used to encode and decode boxes
target_means=[0.0, 0.0, 0.0, 0.0],
# The standard variance used to encode and decode boxes
target_stds=[1.0, 1.0, 1.0, 1.0]),
# Config of loss function for the classification branch
loss_cls=dict(
# Type of loss for classification branch.
type='CrossEntropyLoss',
# RPN usually perform two-class classification,
# so it usually uses sigmoid function.
use_sigmoid=True,
# Loss weight of the classification branch.
loss_weight=1.0),
# Config of loss function for the regression branch.
loss_bbox=dict(
# Type of loss, we also support many IoU Losses and smooth L1-loss. For implementation refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/losses/smooth_l1_loss.py#L56
type='L1Loss',
# Loss weight of the regression branch.
loss_weight=1.0)),
# Type of the RoI head, for more details refer to
# RoI feature extractor for bbox regression.
bbox_roi_extractor=dict(
# Type of the RoI feature extractor. For more details refer to
type='SingleRoIExtractor',
roi_layer=dict(  # Config of RoI Layer
# Type of RoI Layer, for more details refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/ops/roi_align/roi_align.py#L79
type='RoIAlign',
output_size=7,  # The output size of feature maps.
# Sampling ratio when extracting the RoI features.
sampling_ratio=0),
# output channels of the extracted feature.
out_channels=256,
# Strides of multi-scale feature maps. It should be consistent to the architecture of the backbone.
featmap_strides=[4, 8, 16, 32]),
# Type of the bbox head, for more details refer to
# Input channels for bbox head. This is consistent with the out_channels in roi_extractor
in_channels=256,
# Output feature channels of FC layers.
fc_out_channels=1024,
roi_feat_size=7,  # Size of RoI features
num_classes=80,  # Number of classes for classification
bbox_coder=dict(  # Box coder used in the second stage.
# Type of box coder. 'DeltaXYWHBBoxCoder' is applied for most of methods.
type='DeltaXYWHBBoxCoder',
# Means used to encode and decode box
target_means=[0.0, 0.0, 0.0, 0.0],
# Standard variance for encoding and decoding. It is smaller since
# the boxes are more accurate. [0.1, 0.1, 0.2, 0.2] is a conventional setting.
target_stds=[0.1, 0.1, 0.2, 0.2]),
reg_class_agnostic=False,  # Whether the regression is class agnostic.
loss_cls=dict(  # Config of loss function for the classification branch
# Type of loss for classification branch, we also support FocalLoss etc.
type='CrossEntropyLoss',
use_sigmoid=False,  # Whether to use sigmoid.
loss_weight=1.0),  # Loss weight of the classification branch.
loss_bbox=dict(  # Config of loss function for the regression branch.
# Type of loss, we also support many IoU Losses and smooth L1-loss, etc.
type='L1Loss',
# Loss weight of the regression branch.
loss_weight=1.0),
# the initialization of specific layer. For more details, please refer to
init_cfg=[
# initialize shared_fcs layer with Caffe2Xavier
dict(type='Caffe2Xavier',
override=dict(type='Caffe2Xavier', name='shared_fcs')),
# initialize fc_cls layer with Normal
dict(type='Normal',
override=dict(type='Normal', name='fc_cls', std=0.01)),
# initialize fc_cls layer with Normal
dict(type='Normal',
override=dict(type='Normal', name='fc_reg', std=0.001))
],
# number of shared fc layers
num_shared_fcs=2)),
train_cfg=dict(
rpn=dict(  # Training config of rpn
assigner=dict(  # Config of assigner
# Type of assigner. For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/max_iou_assigner.py#L10
type='MaxIoUAssigner',
pos_iou_thr=0.7,  # IoU >= threshold 0.7 will be taken as positive samples
neg_iou_thr=0.3,  # IoU < threshold 0.3 will be taken as negative samples
min_pos_iou=0.3,  # The minimal IoU threshold to take boxes as positive samples
# Whether to match the boxes under low quality (see API doc for more details).
match_low_quality=True,
ignore_iof_thr=-1),  # IoF threshold for ignoring bboxes
sampler=dict(  # Config of positive/negative sampler
# Type of sampler. For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/samplers/random_sampler.py#L8
type='RandomSampler',
num=256,  # Number of samples
pos_fraction=0.5,  # The ratio of positive samples in the total samples.
# The upper bound of negative samples based on the number of positive samples.
neg_pos_ub=-1,
# Whether add GT as proposals after sampling.
# The border allowed after padding for valid anchors.
allowed_border=-1,
# The weight of positive samples during training.
pos_weight=-1,
debug=False),  # Whether to set the debug mode
rpn_proposal=dict(  # The config to generate proposals during training
nms_pre=2000,  # The number of boxes before NMS
max_per_img=1000,  # The number of boxes to be kept after NMS.
nms=dict(  # Config of NMS
type='nms',  # Type of NMS
iou_threshold=0.7),  # NMS threshold
min_bbox_size=0),  # The allowed minimal box size
rcnn=dict(  # The config for the roi heads.
assigner=dict(  # Config of assigner for second stage, this is different for that in rpn
# Type of assigner, MaxIoUAssigner is used for all roi_heads for now. For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/max_iou_assigner.py#L10 for more details.
type='MaxIoUAssigner',
pos_iou_thr=0.5,  # IoU >= threshold 0.5 will be taken as positive samples
neg_iou_thr=0.5,  # IoU < threshold 0.5 will be taken as negative samples
min_pos_iou=0.5,  # The minimal IoU threshold to take boxes as positive samples
# Whether to match the boxes under low quality (see API doc for more details).
match_low_quality=False,
ignore_iof_thr=-1),  # IoF threshold for ignoring bboxes
sampler=dict(
# Type of sampler, PseudoSampler and other samplers are also supported. For more details, please refer to
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/samplers/random_sampler.py#L8
type='RandomSampler',
num=512,  # Number of samples
pos_fraction=0.25,  # The ratio of positive samples in the total samples.
# The upper bound of negative samples based on the number of positive samples.
neg_pos_ub=-1,
# Whether add GT as proposals after sampling.
# The weight of positive samples during training.
pos_weight=-1,
# Whether to set the debug mode
debug=False)),
test_cfg=dict(  # Config for testing hyperparameters for rpn and rcnn
rpn=dict(  # The config to generate proposals during testing
# The number of boxes before NMS
nms_pre=1000,
# The number of boxes to be kept after NMS.
max_per_img=1000,
# Config of NMS
nms=dict(type='nms', iou_threshold=0.7),
# The allowed minimal box size
min_bbox_size=0),
rcnn=dict(  # The config for the roi heads.
score_thr=0.05,  # Threshold to filter out boxes
# Config of NMS in the second stage
nms=dict(type='nms', iou_threshold=0.5),
# Max number of detections of each image
max_per_img=100)),
# parameters with the prefix listed in frozen_parameters will be frozen
frozen_parameters=[
])
# Config to set the checkpoint hook, Refer to
# https://github.com/open-mmlab/mmcv/blob/master/mmcv/runner/hooks/checkpoint.py for implementation.
checkpoint_config = dict(interval=80000)
# The logger used to record the training process.
log_config = dict(interval=50, hooks=[dict(type='TextLoggerHook')])
custom_hooks = [dict(type='NumClassCheckHook')]  # cumstomize hook
dist_params = dict(backend='nccl')  # parameters to setup distributed training, the port can also be set.
log_level = 'INFO'  # the output level of the log.
# use base training model as model initialization.
# workflow for runner. [('train', 1)] means there is only one workflow and the workflow named 'train' is executed once.
workflow = [('train', 1)]
use_infinite_sampler = True  # whether to use infinite sampler
seed = 0  # random seed


## FAQ¶

### Use intermediate variables in configs¶

Some intermediate variables are used in the configs files, like train_pipeline/test_pipeline in datasets. It’s worth noting that when modifying intermediate variables in the children configs, user need to pass the intermediate variables into corresponding fields again. For example, we would like to use multi scale strategy to train a Mask R-CNN. train_pipeline/test_pipeline are intermediate variable we would like modify.

_base_ = './faster_rcnn_r50_caffe_fpn.py'
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='Resize',
img_scale=[(1333, 640), (1333, 672), (1333, 704), (1333, 736),
(1333, 768), (1333, 800)],
multiscale_mode="value",
keep_ratio=True),
dict(type='RandomFlip', flip_ratio=0.5),
dict(type='Normalize', **img_norm_cfg),
dict(type='DefaultFormatBundle'),
]
test_pipeline = [
dict(
type='MultiScaleFlipAug',
img_scale=(1333, 800),
flip=False,
transforms=[
dict(type='Resize', keep_ratio=True),
dict(type='RandomFlip'),
dict(type='Normalize', **img_norm_cfg),
dict(type='ImageToTensor', keys=['img']),
dict(type='Collect', keys=['img']),
])
]
data = dict(
train=dict(pipeline=train_pipeline),
val=dict(pipeline=test_pipeline),
test=dict(pipeline=test_pipeline))


We first define the new train_pipeline/test_pipeline and pass them into data.

Similarly, if we would like to switch from SyncBN to BN or MMSyncBN, we need to substitute every norm_cfg in the config.

_base_ = './faster_rcnn_r50_caffe_fpn.py'