[Trilinos-Users] drop tolerance and ILU IFPACK

[Heroux, Michael A]

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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