fix normalize mode at confusion matrix (replace nans with zeros)

[c00k1ez]

What does this PR do?

Added same behaviour to confusion_matrix as sklearn.metrics.confusion_matrix with normalization while all predict and target values from same class (nan -> 0). Discussed it with @Borda at Slack.
Also fixes #2724

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[c00k1ez]

10 failing tests(
What am I doing wrong?

[williamFalcon]

https://github.com/PyTorchLightning/pytorch-lightning/pull/3465/checks?check_run_id=1103259393

[rohitgr7]

Nothing wrong, It's just the PyTorch version I think. Just replace cm.isnan() with torch.isnan(cm).

[codecov]

Codecov Report

Merging #3465 into master will decrease coverage by 3%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           master   #3465     +/-   ##
========================================
- Coverage      85%     82%     -3%     
========================================
  Files         105     116     +11     
  Lines        8157    9440   +1283     
========================================
+ Hits         6943    7766    +823     
- Misses       1214    1674    +460     

[c00k1ez]

Well, It's a bit weird, All tests at tests/test_classification.py and tests/functional/test_classification.py passed successfully at my local machine.

[SkafteNicki]

The checks are being cancelled because they take too long time (cancelled after 35 min).
From the checks it seems that the last passed test is:
tests/loggers/test_all.py::test_logger_created_on_rank_zero_only[TestTubeLogger]
which means that it is next test that is hanging:
tests/loggers/test_base.py::test_logger_collection

[c00k1ez]

As I understand, it is not connected with my changes, right? So, what should i do now?

[SkafteNicki]

Yes, it does not seem to be related to your PR (sometimes tests just fails)

[awaelchli]

check master, it comes from there :) not your fault @c00k1ez

[c00k1ez]

Ok 👌

[c00k1ez]

Added fix for Issue 1 from #2724.
@SkafteNicki can you please add reviewers?

[pep8speaks]

Hello @c00k1ez! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-09-13 14:00:31 UTC

[SkafteNicki]

Overall LGTM, just smaller comments

[c00k1ez]

Thanks 👍
Resolved all small issues.