tried -ksp_gmres_restart 5000, with residual as below
Linear solver converged at step: 53, final residual: 1.5531e-05 begin solve: iteration #54 Linear solver converged at step: 54, final residual: 1.55013e-05 begin solve: iteration #55 On Thu, May 29, 2014 at 6:01 PM, Vikram Garg <[email protected]> wrote: > Try using a higher number of restart steps, say 500, > > -ksp_gmres_restart 500 > > Thanks. > > > On Thu, May 29, 2014 at 7:00 PM, walter kou <[email protected]> wrote: > >> output from the -ksp_monitor_singular_value ? >> >> 250 KSP Residual norm 8.867989901517e-05 % max 1.372837955534e+05 min >> 1.502965355599e+01 max/min 9.134195611495e+03 >> >> >> >> On Thu, May 29, 2014 at 5:54 PM, Vikram Garg <[email protected]> >> wrote: >> >>> Try the following solver options: >>> >>> -pc_type lu -pc_factor_mat_solver_package superlu >>> >>> >>> What was the output from the -ksp_monitor_singular_value ? >>> >>> >>> Thanks. >>> >>> >>> On Thu, May 29, 2014 at 6:52 PM, walter kou <[email protected]> >>> wrote: >>> >>>> Hi Vikram, >>>> >>>> How to try using just lu or super lu? I am pretty ignorant in playing >>>> with proper ksp options in the command line. >>>> >>>> Could you point out any introductory materials on this? >>>> >>>> Thanks so much. >>>> >>>> >>>> >>>> >>>> On Wed, May 28, 2014 at 11:54 AM, Vikram Garg <[email protected]> >>>> wrote: >>>> >>>>> Hey Walter, >>>>> Have you tried using just lu or super lu ? You >>>>> might also want to check and see whats the output for >>>>> -ksp_monitor_singular_value and increase the gmres restart steps. >>>>> >>>>> Thanks. >>>>> >>>>> >>>>> On Mon, May 26, 2014 at 1:57 PM, walter kou <[email protected]> >>>>> wrote: >>>>> >>>>>> Hi all, >>>>>> I ran a larger case: with elements = 200, and found for each >>>>>> calculation in >>>>>> the iteration, system.final_linear_residual() is about 0.5%. >>>>>> >>>>>> 1) Is the system.final_linear_residual() r = b -A X* (X* is the >>>>>> solution) >>>>>> ? right? >>>>>> >>>>>> 2) It seems final residual is too big, and the equation is not solved >>>>>> well >>>>>> (here |b| is about 1e-4). Does anyone have suggestion in playing with >>>>>> solvers of Ax=b? >>>>>> Here my case is on nonlinear elasticity, and A is almost symmetrical >>>>>> positive definite (only components influenced by boundary conditions >>>>>> will >>>>>> break the symmetry). >>>>>> >>>>>> >>>>>> Also, following the suggestion of Paul, I use -ksp_view and find my >>>>>> solver >>>>>> information is as below: >>>>>> >>>>>> KSP Object: 4 MPI processes >>>>>> type: gmres >>>>>> GMRES: restart=30, using Classical (unmodified) Gram-Schmidt >>>>>> Orthogonalization with no iterative refinement >>>>>> GMRES: happy breakdown tolerance 1e-30 >>>>>> maximum iterations=250 >>>>>> tolerances: relative=1e-08, absolute=1e-50, divergence=10000 >>>>>> left preconditioning >>>>>> using nonzero initial guess >>>>>> using PRECONDITIONED norm type for convergence test >>>>>> PC Object: 4 MPI processes >>>>>> type: bjacobi >>>>>> block Jacobi: number of blocks = 4 >>>>>> Local solve is same for all blocks, in the following KSP and PC >>>>>> objects: >>>>>> KSP Object: (sub_) 1 MPI processes >>>>>> type: preonly >>>>>> maximum iterations=10000, initial guess is zero >>>>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000 >>>>>> left preconditioning >>>>>> using NONE norm type for convergence test >>>>>> PC Object: (sub_) 1 MPI processes >>>>>> type: ilu >>>>>> ILU: out-of-place factorization >>>>>> 0 levels of fill >>>>>> tolerance for zero pivot 2.22045e-14 >>>>>> using diagonal shift to prevent zero pivot >>>>>> matrix ordering: natural >>>>>> factor fill ratio given 1, needed 1 >>>>>> Factored matrix follows: >>>>>> Matrix Object: 1 MPI processes >>>>>> type: seqaij >>>>>> rows=324, cols=324 >>>>>> package used to perform factorization: petsc >>>>>> total: nonzeros=16128, allocated nonzeros=16128 >>>>>> total number of mallocs used during MatSetValues calls =0 >>>>>> not using I-node routines >>>>>> linear system matrix = precond matrix: >>>>>> Matrix Object: () 1 MPI processes >>>>>> type: seqaij >>>>>> rows=324, cols=324 >>>>>> total: nonzeros=16128, allocated nonzeros=19215 >>>>>> total number of mallocs used during MatSetValues calls =0 >>>>>> not using I-node routines >>>>>> linear system matrix = precond matrix: >>>>>> Matrix Object: () 4 MPI processes >>>>>> type: mpiaij >>>>>> rows=990, cols=990 >>>>>> total: nonzeros=58590, allocated nonzeros=64512 >>>>>> total number of mallocs used during MatSetValues calls =0 >>>>>> not using I-node (on process 0) routines >>>>>> >>>>>> >>>>>> >>>>>> /********************************************************* >>>>>> Thanks, >>>>>> >>>>>> Walter >>>>>> >>>>>> >>>>>> On Thu, May 22, 2014 at 12:18 PM, Paul T. Bauman <[email protected]> >>>>>> wrote: >>>>>> >>>>>> > >>>>>> > >>>>>> > >>>>>> > On Thu, May 22, 2014 at 12:11 PM, walter kou <[email protected] >>>>>> >wrote: >>>>>> > >>>>>> >> OK, but libMesh calls a library, defaulting to PETSc if it's >>>>>> installed. >>>>>> >> Which library are you using? >>>>>> >> >>>>>> >> PETSc-3.3 >>>>>> >> >>>>>> > >>>>>> > I recommend checking out the PETSc documentation ( >>>>>> > http://www.mcs.anl.gov/petsc/petsc-as/documentation/) and >>>>>> tutorials. But >>>>>> > you'll want to start with -ksp_view to get the parameters PETSc is >>>>>> using. >>>>>> > >>>>>> >>>>>> ------------------------------------------------------------------------------ >>>>>> The best possible search technologies are now affordable for all >>>>>> companies. >>>>>> Download your FREE open source Enterprise Search Engine today! >>>>>> Our experts will assist you in its installation for $59/mo, no >>>>>> commitment. >>>>>> Test it for FREE on our Cloud platform anytime! >>>>>> >>>>>> http://pubads.g.doubleclick.net/gampad/clk?id=145328191&iu=/4140/ostg.clktrk >>>>>> _______________________________________________ >>>>>> Libmesh-users mailing list >>>>>> [email protected] >>>>>> https://lists.sourceforge.net/lists/listinfo/libmesh-users >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Vikram Garg >>>>> Postdoctoral Associate >>>>> Center for Computational Engineering >>>>> Massachusetts Institute of Technology >>>>> http://web.mit.edu/vikramvg/www/ >>>>> >>>>> http://www.runforindia.org/runners/vikramg >>>>> >>>> >>>> >>> >>> >>> -- >>> Vikram Garg >>> Postdoctoral Associate >>> Center for Computational Engineering >>> Massachusetts Institute of Technology >>> http://web.mit.edu/vikramvg/www/ >>> >>> http://www.runforindia.org/runners/vikramg >>> >> >> > > > -- > Vikram Garg > Postdoctoral Associate > Center for Computational Engineering > Massachusetts Institute of Technology > http://web.mit.edu/vikramvg/www/ > > http://www.runforindia.org/runners/vikramg > ------------------------------------------------------------------------------ Time is money. 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