[petsc-users] Solving NON-Diagonally dominant sparse system

[Kaushik Kulkarni]

Thank you for the inputs.
I tried Barry' s suggestion to use SuperLU, but the solution does not
converge and on doing -ksp_monitor -ksp_converged_reason. I get the
following error:-
240 KSP Residual norm 1.722571678777e+07
Linear solve did not converge due to DIVERGED_DTOL iterations 240
For some reason it is diverging, although I am sure that for the given
system a unique solution exists.

Thanks,
Kaushik

On Tue, Apr 11, 2017 at 1:04 AM, Xiaoye S. Li <xsli at lbl.gov> wrote:

> If you need to use SuperLU_DIST, the pivoting is done statically, using
> maximum weighted matching, so the small diagonals are usually taken care as
> well. It is not as good as partial pivoting, but works most of the time.
>
> Sherry
>
> On Mon, Apr 10, 2017 at 12:07 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>    I would suggest using ./configure --download-superlu and then when
>> running the program -pc_type lu -pc_factor_mat_solver_package superlu
>>
>>    Note that this is SuperLU, it is not SuperLU_DIST.  Superlu uses
>> partial pivoting for numerical stability so should be able to handle the
>> small or zero diagonal entries.
>>
>>     Barry
>>
>> > On Apr 10, 2017, at 1:17 PM, Kaushik Kulkarni <kaushikggg at gmail.com>
>> wrote:
>> >
>> > Hello,
>> > I am trying to solve a 2500x2500 sparse matrix. To get an idea about
>> the matrix structure I have added a file matrix.log which contains the
>> output of MatView() and also the output of Matview_draw in the image file.
>> >
>> > From the matrix structure it can be seen that Jacobi iteration won't
>> work and some of the diagonal entries being very low(of the order of 1E-16)
>> LU factorization would also fail.
>> >
>> > C​an someone please suggest what all could I try next, in order to make
>> the solution converge?
>> >
>> > Thanks,
>> > Kaushik
>> > ​
>> > --
>> > Kaushik Kulkarni
>> > Fourth Year Undergraduate
>> > Department of Mechanical Engineering
>> > Indian Institute of Technology Bombay
>> > Mumbai, India
>> > https://kaushikcfd.github.io/About/
>> > +91-9967687150
>> > <matrix.log><matrix_pattern.png>
>>
>>
>


-- 
Kaushik Kulkarni
Fourth Year Undergraduate
Department of Mechanical Engineering
Indian Institute of Technology Bombay
Mumbai, India
https://kaushikcfd.github.io/About/
+91-9967687150
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