[Trilinos-Users] drop tolerance and ILU IFPACK

[Boman, Erik G]

Try PrecType = "ILUT". I think ILU only works with level-of-fill, not drop tolerance. It would have been nice to have a single class for both ILU variations, or at least give a warning for incorrect use.

Erik

-----Original Message-----
From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-users-bounces at software.sandia.gov] On Behalf Of Lucia Mirabella
Sent: Wednesday, October 29, 2008 12:39 PM
To: trilinos-users at software.sandia.gov
Cc: Heroux, Michael A
Subject: [Trilinos-Users] drop tolerance and ILU IFPACK

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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