chrF not compatible with chrF++, Moses and NLTK for sentence-level smoothing

[ozancaglayan]

Created a new issue for this problem, to detach it from #121
See the comment: #121 (comment)

To summarize, sacreBLEU applies effective order smoothing whereas others smooth with small value eps. The fix is already in my branch for sacreBLEU 2.0.0. The problem is to agree on whether we accept changing behavior for sentence-level chrF for >=2.0.0.

[martinpopel]

Yes, I vote for being compatible with the chrF++ implementation of chrF by default. We can keep the effective-order smoothing as a non-default option, or drop it (for chrF).