From: Vikram Garg <vikram.v.garg@gm...>  20120829 02:26:08

Well, if you use lu, then there should be no 'residual' provided the matrix is invertible. On Tue, Aug 28, 2012 at 9:24 PM, 蔡园武 <yuanwucai@...> wrote: > Good idea, man, but I don't think changing preconditioner can control > the residual error. > > 2012/8/29 Vikram Garg <simulationist@...>: > > 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 > > > > > >  > Cai Yuanwu 蔡园武 > Dept. of Engineering Mechanics, > Dalian University of Technology, > Dalian 116024, China >  Vikram Garg http://users.ices.utexas.edu/~vikram/ http://www.runforindia.org/runners/vikramg 