Documentation for PISM, the Parallel Ice Sheet Model

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petscoptions [2012/07/21 23:33]
Ed Bueler created from kspdiverged
petscoptions [2012/07/21 23:43]
Ed Bueler done for now with separate PETSc solver options FAQ page
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 +====== PETSc options appropriate to SSA solves in PISM ======
 +
 +Jed Brown, [[http://​www.mcs.anl.gov/​petsc/​petsc-2/​miscellaneous/​index.html|a PETSc developer]] and an original PISM author, gave this example of comparing which were the efficient solvers for a saved, invertible linear system that came from an SSA solve. ​ This example, which uses 8  MPI processes, mostly shows that no method of these is outstandingly better than another. See also the page on [[kspdiverged|diagnosing and resolving "KSP diverged"​ errors]].
  
-Jed's original example included an example of comparing which were the efficient solvers for another invertible system that was invertible, using 8  MPI processes: 
 <​code>​ <​code>​
 # Additive Schwarz with overlap 1 # Additive Schwarz with overlap 1
-$ time mpiexec -n 8 ./ex10 -f ~/​pism-run/​SSAFD_ksperror_y-4141.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu+$ time mpiexec -n 8 ./ex10 -f SSAFD_ksperror.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu
 Number of iterations =  19 Number of iterations =  19
 Residual norm 92.3905 Residual norm 92.3905
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 # Umfpack instead of PETSc subdomain solves, slightly faster # Umfpack instead of PETSc subdomain solves, slightly faster
-$ time mpiexec -n 8 ./ex10 -f ~/​pism-run/​SSAFD_ksperror_y-4141.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack+$ time mpiexec -n 8 ./ex10 -f SSAFD_ksperror.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack
 Number of iterations =  19 Number of iterations =  19
 Residual norm 92.3905 Residual norm 92.3905
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 # More overlap, a little better # More overlap, a little better
-$ time mpiexec -n 8 ./ex10 -f ~/​pism-run/​SSAFD_ksperror_y-4141.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack -pc_asm_overlap 2+$ time mpiexec -n 8 ./ex10 -f SSAFD_ksperror.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type asm -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack -pc_asm_overlap 2
 Number of iterations =  14 Number of iterations =  14
 Residual norm 139.529 Residual norm 139.529
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 # No overlap, slower and less robust # No overlap, slower and less robust
-$ time mpiexec -n 8 ./ex10 -f ~/​pism-run/​SSAFD_ksperror_y-4141.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type bjacobi -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack+$ time mpiexec -n 8 ./ex10 -f SSAFD_ksperror.petsc -ksp_type gmres -ksp_norm_type unpreconditioned -ksp_pc_side right -pc_type bjacobi -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack
 Number of iterations =  32 Number of iterations =  32
 Residual norm 153.677 Residual norm 153.677
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 sys     ​0m0.916s sys     ​0m0.916s
  
-unpreconditioned ​norm, less accurate¬†+preconditioned ​norm, less accurate¬†
-$ time mpiexec -n 8 ./ex10 -f ~/​pism-run/​SSAFD_ksperror_y-4141.petsc -ksp_type gmres -ksp_norm_type preconditioned -ksp_pc_side left -pc_type bjacobi -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack+$ time mpiexec -n 8 ./ex10 -f SSAFD_ksperror.petsc -ksp_type gmres -ksp_norm_type preconditioned -ksp_pc_side left -pc_type bjacobi -sub_pc_type lu -sub_pc_factor_mat_solver_package umfpack
 Number of iterations =  18 Number of iterations =  18
 Residual norm 30777.5 Residual norm 30777.5
petscoptions.txt · Last modified: 2012/07/21 23:43 by Ed Bueler
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