On Thu, May 22, 2014 at 11:52 AM, walter kou <[email protected]> wrote:
> The amount of relative change in terms of ||delta U|| is about 1.0e-6 for
> my case with only 8 nodes. That's why I doubt I may not setup the solver
> correctly.
>
>
> If an iterative solver, what's the tolerance?
>
> Are you asking how I solved x in Ax=b?
>
Yes.
>
> I just assembled the system:
> {system.matrix->add_matrix (Ke, dof_indices);
> system.rhs->add_vector (Fe, dof_indices);}
> then called system.solve, where system is a
> <TransientLinearImplicitSystem>.
>
OK, but libMesh calls a library, defaulting to PETSc if it's installed.
Which library are you using?
> I did use the tolerance for the loop of iteration solver. it was 1.0e-5
> for the delta U, and the n-iteration-number = 1000;
>
This explains why you see 1.0r-6 in \Delta U - your tolerance was 1.0e-5
(as stated above)
> The above mainly shows the difference of the first
> iteration/calculation(Ax=b) between one processor and two processors.
>
Right, the residual difference was < 1.0e-10 difference (small) and within
tolerance on \Delta U.
> By the way, What is the typical parameter setup I should use for the
> iterative solver?
>
Entirely problem dependent.
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