Re: nullspaces

Subject: Re: nullspaces

From: "Matthew Knepley" <knepley@xxxxxxxxx>

Date: Tue, 9 May 2006 08:35:35 -0500

Cc: "Matthew Knepley" <petsc-maint@xxxxxxxxxxx>

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Yaron Kretchmer

yaronkretchmer@xxxxxxxxx

Hi all

I have a matrix representing electrical currents (KCL). In my design, there are some elements which are totally isolated from the rest of the circuit, which means that they form the matrix's nullspace.

My questions are:

*) Can I use Petsc to derive the nodes which compose the nullspace

We do not have QR type algorithms in PETSc, but you could use LAPACK or
PLAPACK for dense matrices.

*) Can I then remove them from the KSP? If so, how?

You can use the MatNullSpace architecture to remove these components from a solve.

Matt

Thanks much

Yaron

References:

nullspaces
- From: Yaron Kretchmer