improve speed of Ax=b solve operations for matrices
perform checks similar to matlab: https://de.mathworks.com/help/matlab/ref/mldivide.html
for dense matrices:
- not square operator -> use QR or SVD
- implement check & solver for permuted triangular matrices
- not Hermitian -> LU solver
- all positive / all negative diagonal -> try cholesky
- default to LDL solver otherwise
for sparse:
- check for diagonality -> scale input
- check bandwidth < threshold -> banded solver
- implement check & solver for permuted triangular matrices
- not Hermitian -> LU solver
- all positive / all negative diagonal -> try cholesky
- default to LDL solver otherwise