set default fac = 1 in addSubMatrix
add node-to-node topology
fix matrix assembler
add operator< for MeshItem
add getDictionary()
data_id must be unique
save progress for sparsity generation stuff. TODO generateMeshItemConnectivity()
add getData() and write() in Vector
add solve() in DenseDirectLinearSolver using Gauss
add applyKnownSolution() for dense matrix and vector
fix LinearSystemAssembler
temporally revert the change. data_id becomes non-unique during numbering in current codes.
temporally set MatrixType is dense matrix. CRSMatrix requires sparse pattern
add tests for Mat and LinearSystem