Matt Because I am not clear about what will happen using 'preonly' for large scale problem.
It seems to use a direct solver from below, http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPPREONLY.html Thanks! Wenbo On Mon, Oct 2, 2017 at 5:09 PM, Matthew Knepley <knep...@gmail.com> wrote: > On Sun, Oct 1, 2017 at 9:53 PM, Wenbo Zhao <zhaowenbo.n...@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 <knep...@gmail.com> >> wrote: >> >>> On Sun, Oct 1, 2017 at 6:49 AM, Wenbo Zhao <zhaowenbo.n...@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/> >>> >> >> > > > -- > 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/> >
