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## Motivation

Support DDRNet
Paper: [Deep Dual-resolution Networks for Real-time and Accurate
Semantic Segmentation of Road Scenes](https://arxiv.org/pdf/2101.06085)
official Code: https://github.com/ydhongHIT/DDRNet


There is already a PR
https://github.com/open-mmlab/mmsegmentation/pull/1722 , but it has been
inactive for a long time.

## Current Result

### Cityscapes

#### inference with converted official weights

| Method | Backbone      | mIoU(official) | mIoU(converted weight) |
| ------ | ------------- | -------------- | ---------------------- |
| DDRNet | DDRNet23-slim | 77.8           | 77.84                  |
| DDRNet | DDRNet23 | 79.5 | 79.53 |

#### training with converted pretrained backbone

| Method | Backbone | Crop Size | Lr schd | Inf time(fps) | Device |
mIoU | mIoU(ms+flip) | config | download |
| ------ | ------------- | --------- | ------- | ------- | -------- |
----- | ------------- | ------------ | ------------ |
| DDRNet | DDRNet23-slim | 1024x1024 | 120000 | 85.85 | RTX 8000 | 77.85
| 79.80 |
[config](https://github.com/whu-pzhang/mmsegmentation/blob/ddrnet/configs/ddrnet/ddrnet_23-slim_in1k-pre_2xb6-120k_cityscapes-1024x1024.py)
| model \| log |
| DDRNet | DDRNet23 | 1024x1024 | 120000 | 33.41 | RTX 8000 | 79.53 |
80.98 |
[config](https://github.com/whu-pzhang/mmsegmentation/blob/ddrnet/configs/ddrnet/ddrnet_23_in1k-pre_2xb6-120k_cityscapes-1024x1024.py)
| model \| log |


The converted pretrained backbone weights download link:

1.
[ddrnet23s_in1k_mmseg.pth](https://drive.google.com/file/d/1Ni4F1PMGGjuld-1S9fzDTmneLfpMuPTG/view?usp=sharing)
2.
[ddrnet23_in1k_mmseg.pth](https://drive.google.com/file/d/11rsijC1xOWB6B0LgNQkAG-W6e1OdbCyJ/view?usp=sharing

)

## To do

- [x] support inference with converted official weights
- [x] support training on cityscapes dataset

---------

Co-authored-by: xiexinch <xiexinch@outlook.com>