[petsc-users] Setting GAMG options C code

[Harshad Sahasrabudhe]

Hello,

I am using PCGAMG+KSPBCGS for shift and invert spectral transformation in
SLEPc. I optimized the options that I need for GAMG using command line:

-st_ksp_type bcgs
-st_pc_type gamg
-st_pc_gamg_agg_nsmooths 1
-st_mg_levels_ksp_type chebyshev
-st_mg_levels_pc_type jacobi
-st_mg_levels_ksp_max_it 8
-st_pc_gamg_threshold 0.01

How can I set these options inside my production code? Is okay to use
PetscOptionsSetValue
for setting the options as following?

          ierr = PetscOptionsSetValue(NULL, "-st_mg_levels_ksp_type",
"chebyshev");
          chkerr(ierr);
          ierr = PetscOptionsSetValue(NULL, "-st_mg_levels_pc_type",
"jacobi");
          chkerr(ierr);
          ierr = PetscOptionsSetValue(NULL, "-st_mg_levels_ksp_max_it",
"8");
          chkerr(ierr);
          ierr = PetscOptionsSetValue(NULL, "-st_pc_gamg_threshold",
"0.01");
          chkerr(ierr);

Thanks!
Harshad