[Trilinos-Users] drop tolerance and ILU IFPACK

[Lucia Mirabella]

Thank you Mike and Erik.

I think that in this case, the example code in 
packages/belos/example/BlockCG/BlockPrecCGEpetraExFile.cpp (trilinos 
release 8.0.7) was misleading, in suggesting the use of drop tolerance 
parameter for ILU preconditioner. Anyway, I will use your suggestion to 
detect other unused parameters.

Thanks,

Lucia



Heroux, Michael A wrote:
> Lucia,
>
> As Erik mentioned, drop tolerance is not used by Ifpack_ILU.  One way 
> to detect this kind of problem, and problems of misspelling parameter 
> names, is to check for unused parameters in your list using the 
> unused() method.  The following example (look at the very end of the 
> program) shows how this can be done.
>
> http://trilinos.sandia.gov/packages/docs/r9.0/packages/teuchos/doc/html/ParameterList_2cxx__main_8cpp-example.html#a68
>
> Best regards,
>
> Mike
>
>
> On 10/29/08 1:38 PM, "Lucia Mirabella" <lucia at mathcs.emory.edu> wrote:
>
>     Thank you very much, Mike: I solved that problem implementing your
>     last
>     advice.
>
>     However, I have another one: in my code I am using an ILU
>     preconditioner, following the example that I've found in a BlockCG
>     example (BlockPrecCGEpetraExFile.cpp).
>
>     "
>     std::string PrecType = "ILU"; // incomplete LU
>     int OverlapLevel = 1;
>     Prec = Teuchos::rcp( Factory.Create(PrecType, &*B_rcp,
>     OverlapLevel) );
>     ifpackList.set("fact: drop tolerance", drop_tol_IFPACK);
>     "
>
>     In particular, I am testing the effect of the ILU drop tolerance
>     on the
>     sparsity of L and U factors and on the CPU time and iteration for
>     solving the linear system. The problem is that even changing a lot the
>     drop tolerance (from 1e-9 to 10!), I cannot see any effect.
>
>     Do someone know what this is due to?
>
>     Thanks again,
>
>     Lucia
>
>
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