Hello all, I have a "small" linear of the type M x = y where M = [ A B; C A^T] and x = [x1 x2], y = [y1 y2]. The block-matrix M is small enough to be directly inverted with a sparse direct solver like SparseDirectUMFPACK. I have a couple of questions concerning the "assembly" process for M.
I have A, B and C already assembled as SparseMatrix<double>, and I am thinking of using the BlockMatrix class, that is, to have M as a BlockMatrix with 4 blocks (organized as a 2x2 grid). Trouble is, I cannot seem to find the transpose operation for a SparseMatrix to create the "A^T" block... my guess that can be avoided somehow but I cannot see how to do that in the context of the BlockMatrix classes. If I were to use an iterative solver (GMRES) instead of UMFPACK, could I have "M" to be some generic matrix type (derived from SparseMatrix<double>) for which I override the vmult operation to do what I want? Or is this not a good approach? thanks for helping! -- Mihai
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