Ambraven 
Just a though but building a matrix from another matrix plus a line of ones or just getting a vector that sums all the rows of a matrix should be intuitive with any algebra crate.
tuxmain@Ambraven It can be done in gwrizienn without overhead, but it's not very ergonomic. example for building a matrix https://git.zoai.re/tuxmain/gwrizienn/src/branch/main/examples/ntwe.rs#L77-L83
I wanted to make nice functions for matrix concatenation, but const expressions were not powerful enough to check that the sizes sum up correctly.
Matrices are stored row-wise so row sum should be trivial. (create a vector then iterate on the rows)
