[petsc-users] Issue of mg_coarse_ksp not converge

[Matthew Knepley]

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/~mk51/>
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