Dear all, I am working on the resolution of a non-linear problem via SNES with a large null-space (at least 70% of the equations are trivial). In a nutshell I have a mesh with active and non-active nodes, and the non-active nodes introduces the null-space.
So far I've dealing with it using NGMRES but I want to use a scheme based on NR. However, despite removing the null-space using PETSc's in-build functions the linear solver (KSP+PC) diverges at the first iteration. However, If I remove the non-active nodes and use the same solver (SNES+KSP+PC), which failed before, now I can solve the non-linear system. Any clue? I’m missing something? Thanks, Miguel
