On 11/20/18 2:27 PM, 'Maxi Miller' via deal.II User Group wrote: > how exactly can I understand that? I have to generate a second matrix, which > then will be added to the sparse matrix, but (due to the vector > multiplication) will be a full matrix, something I would like to avoid.
No, you don't generate a matrix. You just store the vectors. Let's say these vectors are x_k and y_k and that the second matrix has the form \sum_k y_k x_k^T Then you implement the vmult function of your "matrix-like" class as void BroydenOperator::vmult (Vector<double> &dst, const Vector<double> &src) const { dst = 0; for (unsigned int k=0; k<n_vectors; ++k) { const double xk_dot_src = x[k] * src; dst.add (xk_dot_src, y[k]); } } This implements the *action* of the matrix without ever storing the elements of the matrix. Take a look at step-20 or step-22 to say more examples of operators for which we don't know the matrix entries. Best W. -- ------------------------------------------------------------------------ Wolfgang Bangerth email: bange...@colostate.edu www: http://www.math.colostate.edu/~bangerth/ -- 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 dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.