Jaekwang, It seems that you are missing constraints.distribute(solution); after solving the linear system. The constrained dofs are set to zero during assembly and this call is necessary to get the correct values for these in the solution as well. You might want to have a look at https://www.dealii.org/8.4.1/doxygen/deal.II/group__constraints.html or step-6.
Best, Daniel -- 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.