[petsc-users] How do constraint dofs work?

[Alexis Marboeuf]

Hello,

I intend to contribute to the Petsc documentation, especially on PetscSF and PetscSection objects. I'm writing an example where I solve a linear elasticity problem in parallel on unstructured meshes. I discretize the system with a finite element method and P1 Lagrange base functions. I only use Petsc basics such as PetscSF, PetscSection, Mat, Vec and SNES objects and I need to implement Dirichlet and/or Neuman boundary conditions. PetscSectionSetConstraintDof and related routines allow to define which dofs are removed from the global system but are kept in local Vec. I don't find much more information about constraint dofs. Can someone explain me how it works? In particular, do I have to manually add terms related to inhomogeneous Dirichlet boundary condition in the RHS? Am I missing something?

Regards,
Alexis Marboeuf

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