Dear Bruno and Wolfgang, Thanks a lot for your responses. Wolfgang kindly gave a concise and clear restatement of my question. So to my understanding it seems that as long as we have defined block vectors and matrices in setup_system properly, and have taken care of correct combinations of trial and test functions within the assembly, we can almost be sure that the rest is handled by deal.ii.
But may I ask about step-44 in which the shape functions (?) are addressed through system_to_component/base_index? Are these (steps 20 and 44,8) just two different approaches as explained in the Handling vector valued problems module? I was wondering when we might need to follow step-44 and for example evaluate i_group and j_group s within the assembly function? Thanks again, Ali On Wed, May 25, 2022 at 2:46 AM Wolfgang Bangerth <bange...@colostate.edu> wrote: > On 5/23/22 17:52, Ali Seddiq wrote: > > > > In step 20 as well as some other steps, terms are added up (in assembly) > to > > construct the building blocks of the system matrix and rhs. But again > how (or > > where) are they addressed in the case of a block matrix? > > In addition to Bruno's answer: If your question is "which block of the > matrix/rhs vector a certain term in the weak form ends up in", then the > answer > is "that depends on which variable the test and trial function belongs > to". > For example, in step-20, if you have a trial and test function that both > are > velocities (as indicated by the [velocity] extractor on the fe_values > object), > then the result of that term ends up in the top left block of the matrix. > Similarly for the other combinations. > > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/09c8d29a-9dbc-ca6b-5bf9-07a243098999%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 dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/CAGCqmDoaCUrz4kf3hg_NpvBgSDRGb5S9G8OPRCvrzdy4pbG3bg%40mail.gmail.com.
