Add `solve_upper_triangular` to `CsrMatrix`
This allows a sparse matrix to be used for efficient solving with a dense LU decomposition.
Add CscBuilder
For partial construction of Csc matrices
Start working on actual LU factorization
Complete basic version of sparse LU factorization
Reformat to compile in old version
Add LU tests
Add upper triangular solve
Complete tests of Sparse LU factorization
The CSC matrix API mirrors the CSR matrix API. However, there
are subtle differences throughout (both in the available
methods and the implementation) that I believe makes any attempt
to avoid the duplicate effort futile.
julianknodt
Andreas Longva
Hantao Hui
Anton