[petsc-users] Issue of mg_coarse_ksp not converge

Wenbo Zhao zhaowenbo.npic at gmail.com
Mon Oct 2 09:43:22 CDT 2017 

Mark,

Thanks for your reply.

On Mon, Oct 2, 2017 at 9:51 PM, Mark Adams <mfadams at lbl.gov> wrote:

> Please send the output with -st_ksp_view and -st_ksp_monitor and we can
> start to debug it.
>
> Test 1 with nonsmooth and preonly is OK
zhaowenbo at ubuntu:~/test_slepc/SPARK/spark$ make NCORE=1 runkr_nonsmooth
mpirun -n 1 ./step-41 \
   -st_ksp_type gmres  -st_ksp_view -st_ksp_monitor  \
   -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 0 \
   -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
   -st_mg_coarse_ksp_type preonly   -st_mg_coarse_ksp_monitor  \
   -eps_nev 1 -eps_ncv 10  -eps_monitor  -log_view > log_nonsmooth 2>&1

Test 2 smooth and preonly is not OK
zhaowenbo at ubuntu:~/test_slepc/SPARK/spark$ make NCORE=1 runkr_smooth
mpirun -n 1 ./step-41 \
   -st_ksp_type gmres -st_ksp_view -st_ksp_monitor  \
   -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 1 \
   -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
   -st_mg_coarse_ksp_type preonly   -st_mg_coarse_ksp_monitor  \
   -eps_nev 1 -eps_ncv 10  -eps_monitor -log_view > log_smooth 2>&1
makefile:43: recipe for target 'runkr_smooth' failed
make: *** [runkr_smooth] Error 91

Test 3 nonsmooth and gmres is not OK
zhaowenbo at ubuntu:~/test_slepc/SPARK/spark$ make NCORE=1 runkr_gmres
mpirun -n 1 ./step-41 \
   -st_ksp_type gmres  -st_ksp_view -st_ksp_monitor  \
   -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 0 \
   -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
   -st_mg_coarse_ksp_type gmres  -st_mg_coarse_ksp_monitor
-st_mg_coarse_ksp_rtol 1.0e-6 \
   -eps_nev 1 -eps_ncv 10  -eps_monitor  -log_view > log_gmres 2>&1
makefile:59: recipe for target 'runkr_gmres' failed
make: *** [runkr_gmres] Error 91

log-files is attached.


You mentioned that B is not symmetric. I assume it is elliptic (diffusion).
> Where does the asymmetry come from?
>
>
It is a two-group diffusion equations, where group denotes neutron enegry
discretisation.
Matrix B consists of neutron diffusion/leakage term, removal term and minus
neutron scatter source term between different energies, when matrix A
denotes neutron fission source.

Diffusion term(Laplace operator) is elliptic and symmetric. Removal term is
diagonal only. However scatter term is asymmetry since scatter term from
high energy to low energy is far greater than the term from low to high.


Wenbo


> On Mon, Oct 2, 2017 at 9:39 AM, Wenbo Zhao <zhaowenbo.npic at gmail.com>
> wrote:
>
>> Matt,
>> Thanks for your reply.
>> For the defalt option doesnt work firstly( -st_ksp_type gmres -st_pc_type
>> gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 1), I tried to test
>> those options.
>>
>> Wenbo
>>
>> On Mon, Oct 2, 2017 at 9:08 PM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Mon, Oct 2, 2017 at 8:30 AM, Wenbo Zhao <zhaowenbo.npic at gmail.com>
>>> wrote:
>>>
>>>> Matt
>>>>
>>>> Because I am not clear about what will happen using 'preonly' for large
>>>> scale problem.
>>>>
>>>
>>> The size of the problem has nothing to do with 'preonly'. All it means
>>> is to apply a preconditioner without a Krylov solver.
>>>
>>>
>>>> It seems to use a direct solver from below,
>>>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/
>>>> KSP/KSPPREONLY.html
>>>>
>>>
>>> However, I still cannot understand why you would change the default?
>>>
>>>   Matt
>>>
>>>
>>>>
>>>> Thanks!
>>>> Wenbo
>>>>
>>>> On Mon, Oct 2, 2017 at 5:09 PM, Matthew Knepley <knepley at gmail.com>
>>>> wrote:
>>>>
>>>>> On Sun, Oct 1, 2017 at 9:53 PM, Wenbo Zhao <zhaowenbo.npic at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Matt,
>>>>>> Thanks for your reply.
>>>>>> It DOES make no sense for this problem.
>>>>>> But I am not clear about the 'preonly' option. Which solver is used
>>>>>> in preonly? I wonder if 'preonly' is suitable for large scale problem such
>>>>>> as 400,000,000 unknowns.
>>>>>> So I tried 'gmres' option and found these error messages.
>>>>>>
>>>>>
>>>>> I mean, why are you setting this at all. Just do not set the coarse
>>>>> solver. The default should work fine.
>>>>>
>>>>>   Thanks,
>>>>>
>>>>>     Matt
>>>>>
>>>>>
>>>>>> Could you give me some suggestions?
>>>>>>
>>>>>> Thanks.
>>>>>>
>>>>>> Wenbo
>>>>>>
>>>>>>
>>>>>> On Mon, Oct 2, 2017 at 12:34 AM, Matthew Knepley <knepley at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> On Sun, Oct 1, 2017 at 6:49 AM, Wenbo Zhao <zhaowenbo.npic at gmail.com
>>>>>>> > wrote:
>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I met some questions when I use PETSC/SLEPC to solve two-group
>>>>>>>> neutron diffusion equations with finite difference method. The grid is
>>>>>>>> 3*3*3, when DOF on each points is 2. So the matrix size is 54*54.
>>>>>>>> It is generalized eigenvalue problem Ax=\lamda Bx, where B is
>>>>>>>> diagonally dominant matrix but not symmetry.
>>>>>>>> EPS is set as below,
>>>>>>>>  ierr = EPSSetProblemType(eps,EPS_GNHEP);CHKERRQ(ierr);¬
>>>>>>>>  ierr = EPSSetWhichEigenpairs(eps,EPS_LARGEST_REAL);CHKERRQ(ierr);¬
>>>>>>>>
>>>>>>>> Krylovschur is used as eps sovler. GAMG is used as PC.
>>>>>>>> I tried agg_nsmooths and mg_coarse_ksp_type. Only non-smooths and
>>>>>>>> preonly is OK.
>>>>>>>>
>>>>>>>
>>>>>>> Why are you setting the coarse solver. This makes no sense.
>>>>>>>
>>>>>>>    Thanks,
>>>>>>>
>>>>>>>     Matt
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Test 1
>>>>>>>> $ make NCORE=1 runkr_nonsmooth
>>>>>>>> mpirun -n 1 ./step-41 \
>>>>>>>>    -st_ksp_type gmres  \
>>>>>>>>    -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 0
>>>>>>>> \
>>>>>>>>    -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
>>>>>>>>    -st_mg_coarse_ksp_type preonly   -st_mg_coarse_ksp_monitor  \
>>>>>>>>    -eps_nev 1 -eps_ncv 10  -eps_monitor  -log_view > log_nonsmooth
>>>>>>>> 2>&1
>>>>>>>>
>>>>>>>> Test 2
>>>>>>>> $ make NCORE=1 runkr_smooth
>>>>>>>> mpirun -n 1 ./step-41 \
>>>>>>>>    -st_ksp_type gmres  \
>>>>>>>>    -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 1
>>>>>>>> \
>>>>>>>>    -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
>>>>>>>>    -st_mg_coarse_ksp_type preonly   -st_mg_coarse_ksp_monitor  \
>>>>>>>>    -eps_nev 1 -eps_ncv 10  -eps_monitor -log_view > log_smooth 2>&1
>>>>>>>> makefile:43: recipe for target 'runkr_smooth' failed
>>>>>>>> make: *** [runkr_smooth] Error 91
>>>>>>>>
>>>>>>>> Test 3
>>>>>>>> $ make NCORE=1 runkr_gmres
>>>>>>>> mpirun -n 1 ./step-41 \
>>>>>>>>    -st_ksp_type gmres  \
>>>>>>>>    -st_pc_type gamg -st_pc_gamg_type agg -st_pc_gamg_agg_nsmooths 0
>>>>>>>> \
>>>>>>>>    -st_ksp_view  -mata AMAT.dat -matb BMAT.dat \
>>>>>>>>    -st_mg_coarse_ksp_type gmres  -st_mg_coarse_ksp_monitor
>>>>>>>> -st_mg_coarse_ksp_rtol 1.0e-6 \
>>>>>>>>    -eps_nev 1 -eps_ncv 10  -eps_monitor  -log_view > log_gmres 2>&1
>>>>>>>> makefile:59: recipe for target 'runkr_gmres' failed
>>>>>>>> make: *** [runkr_gmres] Error 91
>>>>>>>>
>>>>>>>> Log files were attched.
>>>>>>>> The matrix file were also attched as AMAT.dat and BMAT.dat.
>>>>>>>>
>>>>>>>> Is it correct? Or something wrong with my code or commad-line?
>>>>>>>>
>>>>>>>> Thanks!
>>>>>>>>
>>>>>>>> Wenbo
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> 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
>>>>>>>
>>>>>>> https://www.cse.buffalo.edu/~knepley/
>>>>>>> <http://www.caam.rice.edu/%7Emk51/>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> 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
>>>>>
>>>>> https://www.cse.buffalo.edu/~knepley/
>>>>> <http://www.caam.rice.edu/%7Emk51/>
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> 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
>>>
>>> https://www.cse.buffalo.edu/~knepley/
>>> <http://www.caam.rice.edu/%7Emk51/>
>>>
>>
>>
>
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