Running squential and parallel linear solver in the same code?

[Barry Smith]

 The "second" matrices in each run are the ILU factors on each process. So
long as the 0-35 row matrices are the same on each run you are all set.

  BTW: KSPSolve() does not generate an error if it does not converge. Run with
-ksp_converged_reason to see if it converged or not and why.

  Barry


On Wed, 24 Jan 2007, Ben Tay wrote:

> Hi Barry,
> 
> Thanks for your recommendation. I've managed to use mat_view to view the
> matrix. However, there's something which I don't understand. My linear eqns
> consist of 36 pts - so I see 36 rows - 0 to 35.
> 
> For the uniprocessor, I saw 0-35rows. These show the coefficients of my
> matrix. Then there's a repeat of 0-35 rows again. But what are these values?
> I don't understand.
> 
> For the 4 processors, I saw exactly the same 0-35rows. After that I saw 0-8
> rows repeated 4 times. The values are now different, even for the same 1st 0
> row. Some values are missing. I guess there's where my mistakes are.
> 
> Thank you.
> 
> 
> On 1/23/07, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > 
> > 
> > Ben,
> > 
> >   You can use -pc_type redundant -redundant_pc_type lu to solve the
> > linear system with a sequential LU to test if that improves the situation.
> > 
> > Likely your generation of the matrix on 2 processes is wrong, you can run
> > with -mat_view on a small problem with both 1 and 2 processes and see if
> > they are the same in both cases.
> > 
> > I don't think what you propose to do below makes sense,
> > 
> >   Barry
> > 
> > 
> > On Tue, 23 Jan 2007, Ben Tay wrote:
> > 
> > > Hi,
> > >
> > > In my MPI CFD code, I have to solve 2 linear eqns - momentum and poisson
> > > eqn. There's some error in the code and I don't know which one causes
> > the
> > > error. May I know if it is possible to solve 1 eqn in sequential mode
> > while
> > > the other in MPI to pinpoint the error since my code works ok in a
> > > sequential mode.
> > >
> > > I tried to use this for one of the eqn:
> > >
> > >
> > > call
> > >
> > MatCreateSeqAIJ(PETSC_COMM_SELF,size_x*size_y,size_x*size_y,9,PETSC_NULL_INTEGER,A_mat,ierr)
> > >
> > > call VecCreateSeq(PETSC_COMM_SELF,size_x*size_y,b_rhs,ierr)
> > >
> > > but there's error.
> > >
> > > Thank you.
> > >
> > 
> > 
>