On Thu, Jul 23, 2020 at 12:43 PM Daniel Arndt <d.arndt.m...@gmail.com> wrote:
> However, I have two more related questions. BTW, I am a newbie in C++ >> programming. So my questions may seem absurd. >> >> 1. Now that we have a vector holding all nodal point coordinates, and >> another vector holding all nodal point values of the solution. How do we >> access every nodal point coordinates, and at the same time, the associated >> nodal point value within the same loop? >> >> Can you clarify in a short pseudocode example what you are trying to > achieve? > We need to update function v based on solution u in the following loop. for ( x in vector_of_nodal_points ) v(x) = f(x, u(x)) where v(x) and u(x) are the nodal point value for functions v and u, respectively, and f() is some function depending on function u as well as the location of the nodal point. So in this case, we need to access nodal point coordinates and nodal point values of the solution in the same loop. > >> 1. In addition to nodal point values of a solution, are the partial >> derivatives (or gradient) of the solution at each nodal point available in >> deal.ii? >> >> That's basically what DataPostprocessor is doing. In general, you can > loop over all cells and calculate the derivatives locally. Have a look at > FEValuesBase::get_function_gradients ( > https://www.dealii.org/current/doxygen/deal.II/classFEValuesBase.html#ad1f4e0deb5d982e8172d82141c634a67 > ). > > Well, the above function calculates the gradients of a finite element at the quadrature points of a cell, not at the nodal points of a cell. Such a need arises in the following situation. for ( x in vector_of_nodal_points ) v(x) = g(x, u(x), grad u(x)) -- Stay put, practice social distancing, and be safe! Best, --Xuefeng Li, (504)865-3340(phone) Like floating clouds, the heart rests easy Like flowing water, the spirit stays free Loyola University New Orleans New Orleans, Louisiana (504)865-2051(fax) -- 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/CAO2HPGV-p6f7Tp_C%3DcTS9tNTva9gnm3cT8-JHjkviS7bXFxJXQ%40mail.gmail.com.