A paper studying and dissecting Java implementation will be published next week in ICSOFT 2020 Conference, it passed peer review and such (the public launch is on July 7th).
Full repo implementation with some tuned approach on Java implementation and an algorithm (that we name it Compact) were measured and the numbers show a significant improvement.
https://github.com/ciplogic/elprep-study
Full paper content is there:
https://github.com/ciplogic/elprep-study/blob/master/paper/elprep-study.pdf
NB. This is the follow up paper resulting out of Issue #2