This repository is just a backup of the directory source/src_ri from ABACUS.
It would be deleted after my refactor.
However,
the author, @PeizeLin, may need to refer to it in the future.
Besides,
I regard his codes as some kind of artwork or masterpiece, how am I willing to delete them?
So I decide to upload the backup onto Github.
See?
So much to play with in C++11.