This makes sense. What do you think is an appropriate data structure for the storage of the entries associated with the constrained dofs? A FullMatrix or a separate AffineConstraints?
Later, I have to somehow merge this data structure with the condensed system matrix since I have to solve a linear system with it. Best, Simon Wolfgang Bangerth <[email protected]> schrieb am Sa., 28. Okt. 2023, 21:15: > On 10/28/23 12:46, Simon wrote: > > > > After assembling and solving the linear system, I need the uncondensed > system > > matrix and right hand side to perform a sensitivity analysis. > > In particular, I need the rows and entries of the system matrix and RHS > > corresponding to constrained dofs. > > However, the constraints.distribute_local_to_global() function sets > these > > entries all to zero (except the diagonal value of the system matrix). > > My solution to deal with this is to basically copy my assembly function > and, > > instead of distributing the constraints with the constraints object -- > > constraints.distribute_local_to_global() -- > > I distributed them with the cell iterator -- > > cell-> distribute_local_to_global(), > > which does not care about the constraints. > > > > This solution is of course very inefficient as for efficiency and code > re-use. > > As I said, it is basically a copy of my assembly function, > > although most of the system matrix "is already there". > > > > So is there a more efficient way to recover the full system matrix based > on > > the condensed system matrix? > > No. If I tell you that a number x is a sum of two contributions a+b, there > is > no way for you to recover a and b from x. You have to store it somewhere. > > In your case, though, you don't actually need to compute the contributions > twice -- you can just compute it once and then both save the contributions > locally *and* distribute them to the global matrix. In fact, you only need > to > store contributions for constrained degrees of freedom, rather than for > all. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > 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 [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/ad4901fe-d57c-39b6-50f6-1bea81683fea%40colostate.edu > . > -- 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 on the web visit https://groups.google.com/d/msgid/dealii/CA%2BwBsdNs9B1Oowxm%3DLJaA1oJSwcq01uysSL9dp9%2B%2Bwnvui%3DsUw%40mail.gmail.com.
