ER-ACE criterion simplification

[AlbinSou]

As mentioned in continual learning baselines repo, I simplified the ER-ACE criterion so that it does not track the old and current classes anymore but only considers classes in the current batch as current classes. That way the method does not have to be aware of the stream structure, as it is done in the paper. The results are not changed drastically, sometimes better sometimes worst but not a big difference overall.

[coveralls]

Pull Request Test Coverage Report for Build 4342486641

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.008%) to 73.78%

---

Files with Coverage Reduction	New Missed Lines	%
avalanche/training/supervised/er_ace.py	1	60.4%

Totals
Change from base Build 4164094425:	0.008%
Covered Lines:	13850
Relevant Lines:	18772

---

💛 - Coveralls

[AntonioCarta]

Thanks