You are integrating using two quadrature points per direction. Can you raise that to (2*fe.degree+1)?
L. > On 11 Apr 2019, at 10:58, bobspar...@gmail.com wrote: > > Dear all, > > First of all, thanks for the awesome library. I am starting to learn deal.II, > and it is great! The documentation has been extremely helpful so far. > > I am trying to solve the time dependent elastic equation, and there we > naturally have a mass matrix-like for the velocities. To build this mass > matrix, I adapted the function Diffusion::assemble_system from step-52. > However, in my problem the mass matrix has zero determinant, therefore, it is > not invertible. Is there some mistake in the construction of the mass matrix, > or something I am missing? > > I have sent attached a minimal source code that reproduces this error, the > output of a single run, and a file containing the mass matrix. > > I am running deal.II 9.0.0 installed via candi in Ubuntu 18.04. > > Kind regards, > Bob > > -- > 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. > <matrix.txt><output.txt><minimal.cc> -- 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.
