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# Add Modules
In this tutorial, we introduce the basic steps to create your customized modules. Before learning to create your customized modules, it is recommended to learn the basic concept of models in file [models.md](models.md). You can customize all the components introduced in [models.md](models.md), such as **backbone**, **neck**, **head** and **loss**.
- [Add Modules](#add-modules)
- [Add new backbone](#add-new-backbone)
- [Add new necks](#add-new-necks)
- [Add new loss](#add-new-loss)
- [Add a new backbone](#add-a-new-backbone)
- [Add a new neck](#add-a-new-neck)
- [Add a new head](#add-a-new-head)
- [Add a new loss](#add-a-new-loss)
- [Combine all](#combine-all)
In self-supervised learning domain, each model can be divided into following four parts:
## Add a new backbone
- backbone: used to extract image's feature
- projection head: projects feature extracted by backbone to another space
- loss: loss function the model will optimize
- memory bank(optional): some methods, `e.g. odc`, need extract memory bank to store image's feature.
Assume you are going to create a new backbone `NewBackbone`.
## Add new backbone
Assuming we are going to create a customized backbone `CustomizedBackbone`
1.Create a new file `mmselfsup/models/backbones/customized_backbone.py` and implement `CustomizedBackbone` in it.
1. Create a new file `mmselfsup/models/backbones/new_backbone.py` and implement `NewBackbone` in it.
```python
import torch.nn as nn
from ..builder import BACKBONES
@BACKBONES.register_module()
class CustomizedBackbone(nn.Module):
from mmselfsup.registry import MODELS
def __init__(self, **kwargs):
## TODO
@MODELS.register_module()
class NewBackbone(nn.Module):
def forward(self, x):
def __init__(self, *args, **kwargs):
pass
## TODO
def forward(self, x): # should return a tuple
pass
def init_weights(self, pretrained=None):
## TODO
def init_weights(self):
pass
def train(self, mode=True):
## TODO
pass
```
2.Import the customized backbone in `mmselfsup/models/backbones/__init__.py`.
2. Import the new backbone module in `mmselfsup/models/backbones/__init__.py`.
```python
from .customized_backbone import CustomizedBackbone
...
from .new_backbone import NewBackbone
__all__ = [
..., 'CustomizedBackbone'
...,
'NewBackbone',
...
]
```
3.Use it in your config file.
3. Use it in your config file.
```python
model = dict(
...
backbone=dict(
type='CustomizedBackbone',
type='NewBackbone',
...),
...
)
```
## Add new necks
## Add a new neck
we include all projection heads in `mmselfsup/models/necks`. Assuming we are going to create a `CustomizedProjHead`.
You can write a new neck inherited from `BaseModule` from mmengine, and overwrite `forward`. We have a unified interface for weight initialization in mmengine, you can use `init_cfg` to specify the initialization function and arguments, or overwrite `init_weights` if you prefer customized initialization.
1.Create a new file `mmselfsup/models/necks/customized_proj_head.py` and implement `CustomizedProjHead` in it.
We include all necks in `mmselfsup/models/necks`. Assume you are going to create a new neck `NewNeck`.
1. Create a new file `mmselfsup/models/necks/new_neck.py` and implement `NewNeck` in it.
```python
import torch.nn as nn
from mmcv.runner import BaseModule
from mmengine.model import BaseModule
from ..builder import NECKS
from mmselfsup.registry import MODELS
@NECKS.register_module()
class CustomizedProjHead(BaseModule):
@MODELS.register_module()
class NewNeck(BaseModule):
def __init__(self, *args, **kwargs):
super(CustomizedProjHead, self).__init__(init_cfg)
## TODO
super().__init__()
pass
def forward(self, x):
## TODO
pass
```
You need to implement the forward function, which takes the feature from the backbone and outputs the projected feature.
You need to implement the `forward` function, which applies some operations on the output from the backbone and forwards the results to the head.
2.Import the `CustomizedProjHead` in `mmselfsup/models/necks/__init__`.
2. Import the new neck module in `mmselfsup/models/necks/__init__.py`.
```python
from .customized_proj_head import CustomizedProjHead
...
from .new_neck import NewNeck
__all__ = [
...,
CustomizedProjHead,
'NewNeck',
...
]
```
3.Use it in your config file.
3. Use it in your config file.
```python
model = dict(
...,
...
neck=dict(
type='CustomizedProjHead',
type='NewNeck',
...),
...)
...
)
```
## Add new loss
## Add a new head
To add a new loss function, we mainly implement the `forward` function in the loss module.
You can write a new head inherited from `BaseModule` from mmengine, and overwrite `forward`.
1.Create a new file `mmselfsup/models/heads/customized_head.py` and implement your customized `CustomizedHead` in it.
We include all heads in `mmselfsup/models/heads`. Assume you are going to create a new head `NewHead`.
1. Create a new file `mmselfsup/models/heads/new_head.py` and implement `NewHead` in it.
```python
import torch
import torch.nn as nn
from mmcv.runner import BaseModule
from mmengine.model import BaseModule
from ..builder import HEADS
from mmselfsup.registry import MODELS
@HEADS.register_module()
class CustomizedHead(BaseModule):
@MODELS.register_module()
class NewHead(BaseModule):
def __init__(self, *args, **kwargs):
super(CustomizedHead, self).__init__()
## TODO
def __init__(self, loss, **kwargs):
super().__init__()
# build loss
self.loss = MODELS.build(loss)
# other specific initializations
def forward(self, *args, **kwargs):
## TODO
pass
```
2.Import the module in `mmselfsup/models/heads/__init__.py`
You need to implement the `forward` function, which applies some operations on the output from the neck/backbone and computes the loss. Please note that the loss module should be built in the head module for the loss computation.
2. Import the new head module in `mmselfsup/models/heads/__init__.py`.
```python
from .customized_head import CustomizedHead
...
from .new_head import NewHead
__all__ = [..., CustomizedHead, ...]
__all__ = [
...,
'NewHead',
...
]
```
3.Use it in your config file.
3. Use it in your config file.
```python
model = dict(
...
head=dict(
type='NewHead',
...),
...
)
```
## Add a new loss
To add a new loss function, we mainly implement the `forward` function in the loss module. We should register the loss module as `MODELS` as well.
We include all losses in `mmselfsup/models/losses`. Assume you are going to create a new loss `NewLoss`.
1. Create a new file `mmselfsup/models/losses/new_loss.py` and implement `NewLoss` in it.
```python
from mmengine.model import BaseModule
from mmselfsup.registry import MODELS
@MODELS.register_module()
class NewLoss(BaseModule):
def __init__(self, *args, **kwargs):
super().__init__()
pass
def forward(self, *args, **kwargs):
pass
```
2. Import the new loss module in `mmselfsup/models/losses/__init__.py`
```python
...
from .new_loss import NewLoss
__all__ = [
...,
head=dict(type='CustomizedHead')
)
'NewLoss',
...
]
```
3. Use it in your config file.
```python
model = dict(
...
head=dict(
...
loss=dict(
type='NewLoss',
...),
...),
...
)
```
## Combine all
After creating each component, mentioned above, we need to create a `CustomizedAlgorithm` to organize them logically. And the `CustomizedAlgorithm` takes raw images as inputs and outputs the loss to the optimizer.
After creating each component mentioned above, we need to create a new algorithm `NewAlgorithm` to organize them logically. `NewAlgorithm` takes raw images as inputs and outputs the loss to the optimizer.
1.Create a new file `mmselfsup/models/algorithms/customized_algorithm.py` and implement `CustomizedAlgorithm` in it.
1. Create a new file `mmselfsup/models/algorithms/new_algorithm.py` and implement `NewAlgorithm` in it.
```python
# Copyright (c) OpenMMLab. All rights reserved.
import torch
from ..builder import ALGORITHMS, build_backbone, build_head, build_neck
from ..utils import GatherLayer
from mmselfsup.registry import MODELS
from .base import BaseModel
@ALGORITHMS.register_module()
class CustomizedAlgorithm(BaseModel):
@MODELS.register_module()
class NewAlgorithm(BaseModel):
def __init__(self, backbone, neck=None, head=None, init_cfg=None):
super(SimCLR, self).__init__(init_cfg)
super().__init__(init_cfg)
pass
## TODO
def extract_feat(self, inputs, **kwargs):
pass
def forward_train(self, img, **kwargs):
def loss(self, inputs, data_samples, **kwargs):
pass
## TODO
def predict(self, inputs, data_samples, **kwargs):
pass
```
2.Import the module in `mmselfsup/models/algorithms/__init__.py`
2. Import the new algorithm module in `mmselfsup/models/algorithms/__init__.py`
```python
from .customized_algorithm import CustomizedAlgorithm
...
from .new_algorithm import NewAlgorithm
__all__ = [..., CustomizedAlgorithm, ...]
__all__ = [
...,
'NewAlgorithm',
...
]
```
3.Use it in your config file.
3. Use it in your config file.
```python
model = dict(
type='CustomizedAlgorightm',
type='NewAlgorithm',
backbone=...,
neck=...,
head=...)
head=...,
...
)
```