Hi Nathaniel, Maybe a look at LinearOperator <https://dealii.org/9.6.0/doxygen/deal.II/classLinearOperator.html>? This class can wrap linear combinations of the operators as a new linear operator with storage of a few std::function members, lightweight and easy to use.
Regards, Chengjiang Yin 在2025年8月20日星期三 UTC+8 05:21:25<Nathaniel Shaffer> 写道： > Howdy, > > I am implementing a matrix-free shift-and-invert eigensolver for Ax = λBx, > where A and B are both symmetric positive-definite MatrixFreeOperators. In > the inverse iteration, I need to do a linear solve with the matrix M = A - > σB. Since I can't just pass A - σB into, say, SolverCG::solve(), I need to > make a new operator for M, call it ShiftedOperator. I'm aware of two > strategies to do this, assuming A and B already exist. > > 1. Derive a new class from MatrixFreeOperators::Base and implement > apply_add() and calculate_diagonal() methods. > > 2. Create a new class, not derived from anything, that just stores const > references to A and B and implements a vmult() method in order to meet the > requirements of SolverCG::solve(). > > In both cases, the actual work is being forwarded to the A and B > operators, and the new ShiftedOperator just combines those results as > needed. Are there strong technical reasons to prefer one approach over the > other? If I only need M for this linear solve, is there added value in > having the full MatrixFreeOperator functionality? Perhaps I've overlooked > something about preconditioning? > > Cheers, > Nathaniel > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/dealii/63703ec3-bd40-4673-9263-2df985f74777n%40googlegroups.com.
