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 petscoptions [2012/07/21 23:33]Ed Bueler created from kspdiverged petscoptions [2012/07/21 23:41]Ed Bueler 2012/07/21 23:43 Ed Bueler done for now with separate PETSc solver options FAQ page2012/07/21 23:41 Ed Bueler 2012/07/21 23:33 Ed Bueler created from kspdiverged 2012/07/21 23:43 Ed Bueler done for now with separate PETSc solver options FAQ page2012/07/21 23:41 Ed Bueler 2012/07/21 23:33 Ed Bueler created from kspdiverged Last revision Both sides next revision Line 1: Line 1: + ====== PETSc options appropriate to SSA solves in PISM ====== - 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: + 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. ​ 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 Line 12: Line 13: # 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 Line 21: Line 22: # 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 Line 30: Line 31: # 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 Line 38: Line 39: 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