Some other methods to be aware of

[ChrisRackauckas]

• https://www.math.purdue.edu/~xiaj/work/fasthss.pdf
• https://www.osti.gov/servlets/purl/15003389
• https://epubs.siam.org/doi/abs/10.1137/050639028

[dlfivefifty]

Note there are two different definitions of semiseparable matrices. These methods relate to the more general hierarchical versions which aren't supported yet.

There's a derelict package https://github.com/JuliaLinearAlgebra/HierarchicalMatrices.jl that is also connected.

[ChrisRackauckas]

https://github.com/bonevbs/HssMatrices.jl