From: Vikram Garg <simulationist@gm...>  20120829 02:07:14

Yuanwu, To set the lu preconditioner type just add the following to the command you use to execute: pc_type lu . If you want to use some other kind of preconditioner you can just change lu to whatever type you want (ilu, jacobi etc) I believe the default is jacobi. Warning: If your problem sizes are really large then lu might take a while. Just try it out first and then you can try ilu if its too slow. Thanks. On Tue, Aug 28, 2012 at 9:02 PM, 蔡园武 <yuanwucai@...> wrote: > 2012/8/29 Vikram Garg <simulationist@...>: > > Hey Yuanwu, > > Can you tell us what kind of linear solver options > you > > are using (the method, preconditioner options passed at runtime) ? > > I used the default option. (I don't know what's the default?) > #EquationSystems > n_systems()=1 > System #0, "homogenization_elastic_3D_plate" > Type "LinearImplicit" > Variables="u" "v" "w" > Finite Element Types="LAGRANGE" "LAGRANGE" "LAGRANGE" > Approximation Orders="FIRST" "FIRST" "FIRST" > n_dofs()=648 > n_local_dofs()=648 > n_constrained_dofs()=198 > n_local_constrained_dofs()=198 > n_vectors()=13 > n_matrices()=1 > DofMap Sparsity > Average OnProcessor Bandwidth <= 84 > Average OffProcessor Bandwidth <= 0 > Maximum OnProcessor Bandwidth <= 144 > Maximum OffProcessor Bandwidth <= 0 > DofMap Constraints > Number of DoF Constraints = 198 > Average DoF Constraint Length= 1 > > > If you > > are using the same stiffness matrix (K) and just changing the rhs (F), > > That's just what I'm doing. > > > then > > you might actually be better of just using the LU preconditioner for one > > load and reusing it for the others. > > How to set it in my code? Can you give me a simple example? > Thanks for your answer! > > > > > Thanks. > > > > On Tue, Aug 28, 2012 at 8:45 PM, 蔡园武 <yuanwucai@...> wrote: > >> > >> Hi, guys, > >> I have a LinearImplicitSystem, solved with a sequential of different > >> force vectors (rhs). > >> Actually I defined different 'Fe' assemble function using a 'loadcase' > >> indicator. In main function, I set the 'loadcase' value, call > >> system.solve(), then es.reinit(), set a new 'loadcase' value, and > >> solve() again. > >> But I found that for some 'loadcase', the solver converged badly, like: > >> > >> loadcase1: Linear solver converged at step: 10736, final residual: > >> 2.00331e21 > >> loadcase2: Linear solver converged at step: 8549, final residual: > >> 2.10685e21 > >> loadcase3: Linear solver converged at step: 8, final residual: > 1.38269e07 > >> loadcase4: Linear solver converged at step: 0, final residual: 0.463112 > >> loadcase5: Linear solver converged at step: 0, final residual: 0.463112 > >> loadcase6: Linear solver converged at step: 0, final residual: 0.463112 > >> > >> In loadcase3, Linear solver converged at step 8, final resudual is not > >> small enough. It's very strange that the loadcases after this didn't > >> run? (converged at step 0?) The results are wrong and unbelievable. > >> But if I solve loadcase3 after all the other loadcases, then loadcase > >> 4,5,6 will be all right. Don't know why? > >> > >> Can I mannually control the final resudual tolerance? I did set a > >> parameter in es: > >> es.parameters.set<unsigned int> ("linear solver maximum > >> iterations") = 20000; > >> es.parameters.set<Real> ("linear solver tolerance") = TOLERANCE; > >> > >> Thanks for your help！ > >>  > >> Cai Yuanwu 蔡园武 > >> Dept. of Engineering Mechanics, > >> Dalian University of Technology, > >> Dalian 116024, China > >> > >> > >> >  > >> Live Security Virtual Conference > >> Exclusive live event will cover all the ways today's security and > >> threat landscape has changed and how IT managers can respond. > Discussions > >> will include endpoint security, mobile security and the latest in > malware > >> threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > >> _______________________________________________ > >> Libmeshusers mailing list > >> Libmeshusers@... > >> https://lists.sourceforge.net/lists/listinfo/libmeshusers > > > > > > > > > >  > > Vikram Garg > > PhD Candidate > > Institute for Computational and Engineering Sciences > > The University of Texas at Austin > > > > http://users.ices.utexas.edu/~vikram/ > > http://www.runforindia.org/runners/vikramg > > > > > >  > Cai Yuanwu 蔡园武 > Dept. of Engineering Mechanics, > Dalian University of Technology, > Dalian 116024, China >  Vikram Garg PhD Candidate Institute for Computational and Engineering Sciences The University of Texas at Austin http://users.ices.utexas.edu/~vikram/ http://www.runforindia.org/runners/vikramg 