[petsc-users] A qustion of PETSc

[Matthew Knepley]

On Tue, May 22, 2012 at 5:17 AM, w_ang_temp <w_ang_temp at 163.com> wrote:

> Hello
>      I am a beginner of PETSc.I find the petsc-users lists is very useful,
> however I do not know how to ask a question in it. So can you tell me? And
> below is what I want to ask.
>     I am solving Ax=b with PETSc. And I only use it in a fortran
> subroutine to get x ,then the main function of my program use x to do other
> things. The question is that: when the process is 1(mpiexec -n 1),the
> result of my program is ok, but when the process is more than 1 the result
> is wrong.
>

"Wrong" is not an acceptable description. I suspect that you do not
understand that only part of a Vec
is stored on each MPI process. First, get the book Using MPI, and then read
the PETSc manual
section on vectors.

  Thanks,

     Matt


>     So where could be wrong? Can you give me some hints on how I can
> debug? Thanks.
>                                   Jim
>
-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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