Hey Yuanwu,
Can you tell us what kind of linear solver options
you are using (the method, preconditioner options passed at runtime) ? If
you are using the same stiffness matrix (K) and just changing the rhs (F),
then you might actually be better of just using the LU preconditioner for
one load and reusing it for the others.
Thanks.
On Tue, Aug 28, 2012 at 8:45 PM, 蔡园武 <[email protected]> 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:
> 2.00331e-21
> loadcase2: Linear solver converged at step: 8549, final residual:
> 2.10685e-21
> loadcase3: Linear solver converged at step: 8, final residual: 1.38269e-07
> 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
>
>
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--
Vikram Garg
PhD Candidate
Institute for Computational and Engineering Sciences
The University of Texas at Austin
http://users.ices.utexas.edu/~vikram/
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