[Trilinos-Users] AztecOO: not enough memory for ILUT

Heroux, Michael A maherou at sandia.gov
Wed Feb 27 13:23:34 MST 2008


Can you tell me what parameter values you are setting for ILUT?  Also, are you performing any local reordering for the preconditioner, e.g., RCM ?


On 2/27/08 11:28 AM, "Tiziano Passerini" <tiziano.passerini at polimi.it> wrote:

Good morning,

I downloaded and compiled Trilinos 8.0.5 and now I'm using AztecOO to
solve a linear system A * x = b coming from finite element spatial
discretization of Navier-Stokes equations. It's not exactly a big
system (200k unknowns) but still I have some unexpected troubles.

I'm running AztecOO on a single processor (no MPI support); I use
gmres solver, with the builtin domain decomposition preconditioner and
subdomain solver ILUT.

Actually my matrix A is ill conditioned, and I played a little with
AztecOO solver params to get convergence in a reasonable number of
iterations. I increased the size of the krylov space, added row
scaling to the matrix and most of all I increased ILUT fill-in. This
is the point, since for large values of ILUT fill-in I got

"ERROR: not enough memory for ILUT. Decrease fill-in or increase drop

However, I'm running my job on a server with 32 GB RAM and 64 bit cpu,
and my job aborts after filling less than 3 GB RAM.

Is that an expected behaviour?

Thanks in advance for any suggestion.

Tiziano Passerini

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