Dear Jean-Paul, Thanks for your answer! Still, I am not sure if I understand the code. The main issue seems to be that both blocks in every if else path are the exactly the same. For instance,
if (apply_dirichlet_bc == true) > VectorTools::interpolate_boundary_values > <http://dealii.org/developer/doxygen/deal.II/namespaceVectorTools.html#a9f3e3ae1396811f998cc35f94cbaa926> > (dof_handler_ref, > boundary_id, > Functions::ZeroFunction<dim> > <http://dealii.org/developer/doxygen/deal.II/classFunctions_1_1ZeroFunction.html> > (n_components), > constraints, > fe.component_mask > <http://dealii.org/developer/doxygen/deal.II/classFiniteElement.html#ace1f6cf0a9f0eb472be4df56743851aa> > (x_displacement)); > else > VectorTools::interpolate_boundary_values > <http://dealii.org/developer/doxygen/deal.II/namespaceVectorTools.html#a9f3e3ae1396811f998cc35f94cbaa926> > (dof_handler_ref, > boundary_id, > Functions::ZeroFunction<dim> > <http://dealii.org/developer/doxygen/deal.II/classFunctions_1_1ZeroFunction.html> > (n_components), > constraints, > fe.component_mask > <http://dealii.org/developer/doxygen/deal.II/classFiniteElement.html#ace1f6cf0a9f0eb472be4df56743851aa> > (x_displacement)); > What is the use of having if-else in this situation? Also, in your answer you mentioned that in the second call (iteration == 1), only homogeneous constrains will be built. I also cannot see this from the code. Perhaps this part is interacting with some other part of the code in a way I cannot see? Thanks for the help, Lucas Campos On 28 August 2017 at 17:03, Jean-Paul Pelteret <jppelte...@gmail.com> wrote: > Hi Lucas, > > So it sounds as if you've already worked out what's happening here. We > consider 3 cases, namely what to do for newton iteration equal to 0, equal > to 1, and greater than 1. > > For iteration == 0 and iteration == 1, the early return on line 2468 > <https://github.com/dealii/dealii/blob/master/examples/step-44/step-44.cc?utf8=%E2%9C%93#L2468> > is not satisfied and we have to build some dirichlet constraints. Which > constraints are build is governed by the iteration number: if it is equal > to zero, then apply_dirichlet_BC > <https://github.com/dealii/dealii/blob/master/examples/step-44/step-44.cc?utf8=%E2%9C%93#L2471> > is set true and we build non-homogeneous constraints (the "if" case). On > the next visit to this function (iteration == 1) this flag is set to false > and we build only homogeneous constraints (the "else" case). At subsequent > iterations we use the early return that I previously mentioned to make no > further changes to the existing constraint matrix. This is because it is > already filled with the homogeneous constraints, which is what we want for > all newton iterations > 0. > > Does this make sense? > > Regards, > Jean-Paul > > On Monday, August 28, 2017 at 4:14:31 PM UTC+2, Lucas Campos wrote: >> >> > This calculation does not happen anyway, because of the early return in >> line 2466. >> >> Just a minor correction for the previous sentence: The guard on line 2466 >> will be true only on the second iterations. The else paths will still be >> taken at least once. >> >> On Monday, 28 August 2017 16:02:01 UTC+2, Lucas Campos wrote: >>> >>> Dear all, >>> >>> First of all, thanks for the great library! I spent the last few days >>> reading your (very!) extensive >>> documentation and I think it will be really useful for me in the near >>> future. >>> >>> Right now I am struggling a bit on understanding some things on step-44. >>> Most pressing right >>> now is that, in Section Solid::make_constraints of the tutorials, we >>> have >>> >>> > However, since we are dealing with an iterative Newton method, it >>> should be noted >>> > that any displacement constraints should only be specified at the >>> zeroth iteration >>> > and subsequently no additional contributions are to be made since the >>> constraints >>> > are already exactly satisfied. >>> >>> However, reading the code underneath, the code under the if-else blocks >>> are the same (around >>> line 2490 of step-44.cc). That is to say, we would run the same >>> computation whether the condition >>> is true or false. This calculation does not happen anyway, because of >>> the early return in line 2466. >>> If we disregard this early return, would this code be wrong, or is there >>> something I am not seeing? >>> >>> Bests, >>> Lucas >>> >> -- > 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 a topic in the > Google Groups "deal.II User Group" group. > To unsubscribe from this topic, visit https://groups.google.com/d/ > topic/dealii/TSUwtKqcotY/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > dealii+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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. 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