Hi guys, I am trying to solve a singular matrix that results from the discretization of a Poisson equation with Neumann boundary conditions. In this case the null space consists of a constant vector. According to the manual MatNullSpaceCreate should be used to construct the null space. Since the constant functions are not needed when providing basis vectors, I am wondering what I should put as basis vectors? My code is now:
PetscInt zero=0 MatNullSpaceCreate(PETSC_COMM_WORLD,PETSC_TRUE,zero,???,&nsp); KSPSetNullSpace(ksp,nsp); If anybody knows what I should put at the question marks, that would be of great help. Thanks! Ben
