Open source project that needs performance optimizations

Yes, I think it is worth evaluating what available at:

https://cran.r-project.org/web/views/HighPerformanceComputing.html

and as a thesis to tackle a "real-life" use case where R language and some of those High Performance Computing packages
are used to solve problems about.
Or you may implement a new R package to provide solution to a performance optimization scenario of your interest.

Also consider what available at:

http://www.teraproc.com/front-page-posts/r-on-demand/


Best,

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GG