[petsc-users] Convergence is different with different processors

[w_ang_temp]

I use the two commands in the same project. The first is divergent while the second is convergent.
nohup mpiexec -n 4 ./ex4f -ksp_type bcgs -pc_type bjacobi -ksp_rtol 1.0e-5 -ksp_converged_reason >out.txt &
nohup mpiexec -n 8 ./ex4f -ksp_type bcgs -pc_type bjacobi -ksp_rtol 1.0e-5 -ksp_converged_reason >out.txt &
So what is the reason?
Thanks.                    Jim





>> 2013-02-07 13:16:51，"Matthew Knepley" <knepley at gmail.com> 写道：

>> On Thu, Feb 7, 2013 at 12:11 AM, w_ang_temp <w_ang_temp at 163.com> wrote:

>> Hello,
>>     I use the same project, but I find that when different number of processors is choosed,
>> the convergence is different. For example, when the processors are 4, it is divergent; when
>> the processors are 8, it is convergent.
>>     So what is the reason?



>It is likely that your preconditioner changed.


  > Matt
 
>>     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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