[petsc-users] Questions about MatConvert BAIJ to AIJ

[Barry Smith]

   As I think I said earlier: ILU will behave differently with BAIJ and AIJ format. With BAIJ it uses a point block factorization (doing an ILU treating each block in the matrix as a single point (and doing a dense factorization for the inverse) while AIJ ignores the block size and just uses a point ILU. So in general the convergence with BAIJ vs AIJ and ILU will be different; usually BAIJ will converge better but it need not.

   Barry

> On Mar 18, 2015, at 1:23 PM, Chung-Kan Huang <ckhuangf at gmail.com> wrote:
> 
> Sorry I didn't state my problem more accurate.  The entries in the input matrixes and vectors​ are correct -- they have right values and correct nonzero structure.
> The KSP was setup so I can solve the lienar systems for an unsteady state convective problem.
> I use KSPBCGS + PCILU and so far I only try sequential on a very small problem.
> I wonder if blocked ilu is actually used in  MATBAIJ2MATAIJ case.
>  
> Thanks,
>  
>