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 > ------------------------------------------------------------------------------ Time is money. 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