[petsc-users] Values of a column in a parallel matrix

[Barry Smith]

> On Mar 20, 2017, at 6:07 PM, Daralagodu Dattatreya Jois, Sathwik Bharadw <sdaralagodudatta at wpi.edu> wrote:
> 
> Hey all,
> 
>  I am using  AIJ matrix to solve Laplace problem in finite element framework. To apply Neumann boundary conditions I need to obtain values of first and last few columns and subtract it with the corresponding right hand side vector. I understand that MatGetColumnVector andMatGetValues are not collective. Is there any other alternative petsc calls to achieve this in parallel? 

  Hmm, I think you mean non-zero Dirichlet boundary conditions. In that case the recommended approach is calling MatZeroRows() or if you want to preserve symmetry MatZeroRowsColumns(). There are also MatZeroRowsLocal() and MatZeroRowsColumnsLocal() and a few other variants.

  Barry


>   
> Thanks,
> Sathwik