Fix floordiv warning.

[JiayuXu0]

Motivation

In SOLO code, floordiv is deprecated, and its behavior will change in a future version of pytorch.

Modification

torch.div(a, b, rounding_mode='trunc') is used to replace floordiv.

[CLAassistant]

All committers have signed the CLA.

[RangiLyu]

The unit tests of pytorch<=1.7 failed. MMDetection needs to support all versions of pytorch >= 1.6.

[JiayuXu0]

If we add a conditional selection (torch version>=1.8 or torch version <1.8) before calculation, is it ok？

[ZwwWayne]

We can implement a floordiv wrapper that handles different pytorch versions, and use that wrapper uniformly in the head.

[JiayuXu0]

Thanks for your suggestion. I have modify the code and wait for your review.

[codecov]

Codecov Report

Merging #8648 (0931ee2) into dev (2f249ff) will increase coverage by 0.00%.
The diff coverage is 77.77%.

@@           Coverage Diff           @@
##              dev    #8648   +/-   ##
=======================================
  Coverage   64.07%   64.08%           
=======================================
  Files         361      361           
  Lines       29528    29536    +8     
  Branches     5021     5022    +1     
=======================================
+ Hits        18920    18927    +7     
- Misses       9591     9592    +1     
  Partials     1017     1017           

Flag	Coverage Δ
unittests	64.08% <77.77%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet/utils/misc.py	62.22% <71.42%> (+0.68%)	⬆️
mmdet/models/dense_heads/solo_head.py	65.26% <100.00%> (+0.07%)	⬆️
mmdet/models/dense_heads/solov2_head.py	10.13% <100.00%> (+0.30%)	⬆️
mmdet/datasets/pipelines/transforms.py	75.80% <0.00%> (-0.17%)	⬇️
mmdet/core/post_processing/bbox_nms.py	79.10% <0.00%> (+4.47%)	⬆️

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[hhaAndroid]

Actually, you can use torch.floor_divide directly

[JiayuXu0]

torch.floor_divide() is deprecated and will be removed in a future PyTorch release.
https://pytorch.org/docs/stable/generated/torch.floor_divide.html

[ZwwWayne]

We need to migrate the modification in MMDet 3.0

[JiayuXu0]

We need to migrate the modification in MMDet 3.0

Should I summit a new pull request to branch dev-3.x? or it will be merged to 3.x automatically?

[BIGWangYuDong]

@JiayuXu0 Hi, you can checkout from dev-3.x and create a new PR to dev-3.x. Thanks for your PR!