Change dict update order

[antoniolanza1996]

Motivation

This PR solves problem 2 described here: open-mmlab/mmocr#292: if you run training with cfg.resume_from = 'epoch_50.pth', all the checkpoints created during this resumed training (e.g. epoch_51.pth, epoch_52.pth, epoch_53.pth) still continue to have epoch and iter equal to the values in epoch_50.pth.

Modification

With this PR I fixed the dict update order. In particular, meta.update(self.meta) should be done before meta.update(epoch=self.epoch + 1, iter=self.iter) because self.meta contains epoch and iter from resumed checkpoint.

[CLAassistant]

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[yeliudev]

In downstream repos like mmdetection/mmocr, some other meta information (e.g. old mmdet_version/mmocr_version) from the old checkpoint will still be saved in self.meta, and override the new checkpoints when resuming using newer mmdetection/mmocr.

[codecov]

Codecov Report

Merging #1108 (9f36da0) into master (004c006) will increase coverage by 0.35%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1108      +/-   ##
==========================================
+ Coverage   67.62%   67.98%   +0.35%     
==========================================
  Files         159      159              
  Lines       10283    10416     +133     
  Branches     1857     1896      +39     
==========================================
+ Hits         6954     7081     +127     
- Misses       2964     2967       +3     
- Partials      365      368       +3     

Flag	Coverage Δ
unittests	67.98% <100.00%> (+0.35%)	⬆️

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

Impacted Files	Coverage Δ
mmcv/runner/epoch_based_runner.py	83.80% <100.00%> (+1.11%)	⬆️
mmcv/runner/iter_based_runner.py	57.85% <100.00%> (+1.02%)	⬆️
mmcv/runner/hooks/evaluation.py	86.70% <0.00%> (-1.46%)	⬇️
mmcv/utils/parrots_wrapper.py	60.71% <0.00%> (-0.31%)	⬇️
mmcv/cnn/utils/weight_init.py	91.34% <0.00%> (-0.04%)	⬇️
mmcv/image/__init__.py	100.00% <0.00%> (ø)
mmcv/utils/__init__.py	88.23% <0.00%> (ø)
mmcv/image/io.py	88.46% <0.00%> (+0.08%)	⬆️
mmcv/image/geometric.py	94.67% <0.00%> (+0.47%)	⬆️
... and 6 more

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[zhouzaida]

LGTM

[ZwwWayne]

LGTM, can be merged after adding comments of explanation.