[SciPy-user] Using umfpack to calculate a incomplete LU factorisation (ILU)

Nils Wagner nwagner@iam.uni-stuttgart...
Tue Mar 6 14:11:34 CST 2007


On Tue, 06 Mar 2007 21:34:14 +0200
  Neilen Marais <nmarais@sun.ac.za> wrote:
> I'm trying to get an incomplete LU factorisation of a 
>sparse matrix using
> scipy.linsolve.splu. It's using umfpack as far as I can 
>tell. I'm telling
> it to drop elements using the drop_tol keyword argument, 
>though it seems
> to be having no effect:
> 
> In [135]: splu(A, drop_tol=1.0).nnz
> Use minimum degree ordering on A'+A.
> Out[135]: 6894814
> 
> In [136]: splu(A, drop_tol=0.00001).nnz
> Use minimum degree ordering on A'+A.
> Out[136]: 6894814
> 
> In [137]: splu(A, drop_tol=1000).nnz
> Use minimum degree ordering on A'+A.
> Out[137]: 6894814
> 
> In [138]: splu(A, drop_tol=10000000000.).nnz
> Use minimum degree ordering on A'+A.
> Out[138]: 6894814
> 
> In [139]: splu(A, 
>drop_tol=100000000000000000000000.).nnz
> Use minimum degree ordering on A'+A.
> Out[139]: 6894814
> 
> In [140]: splu(A, drop_tol=0.000000000000000001).nnz
> Use minimum degree ordering on A'+A.
> Out[140]: 6894814
> 
> Am I doing or understanding something worng? I'm using a 
>recent SVN build:
> 
> In [19]: scipy.version.version
> Out[20]: '0.5.3.dev2827'
> 
> Any help, or pointers to better routines better suited 
>to ILU generation
> welcomed!
> 
> Thanks
> Neilen
> 
> -- 
> you know its kind of tragic 
> we live in the new world
> but we've lost the magic
> -- Battery 9 (www.battery9.co.za)
> 
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Neilen,

You might be interested in ILUPACK

http://www.math.tu-berlin.de/ilupack/
  
Nils


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