From my reading of the SuiteSparse: In order to use one of the direct solvers, the CSC sparse matrix is converted to an internal type,
Sparse. Unfortunately, at that point the memory used for the matrix is duplicated because SuiteSparse uses its internal storage to operate on the matrix.
If this is true, it really becomes a prohibiting factor when dealing with large systems of coupled linear algebraic equations. What is the solution? I don’t know, but I suspect that a true Julia-only solver would need to be written.