Gauss elimination on Petsc matrices

[Barry Smith]

On Fri, 22 Jun 2007, Toby Young wrote:

> 
> Dear Petsc-dev;
> 
> Sorry to bring this up again.
> 
> I am trying to fit Dirchlet boundary conditions on a matrix and retain
> a symmetric matrix after this operation and have run into some difficulty.
> 
> Let me pose my question in another way: Is there a Gaussian elimination in
> the form of an LU decomposition (for example) implemented in Petsc?

   yes, there are a wide variety of LU solvers in PETSc both sequential and 
parallel. Take a look at 
http://www-unix.mcs.anl.gov/petsc/petsc-as/documentation/linearsolvertable.html
The simpliest usage sequential is simply -ksp_type preonly -pc_type lu

   Barry


 
> > It would be more useful in my case to assemble the system, apply boundary
> conditions and then solve; not apply boundary conditions while assembling
> the matrix as has been helpfully suggested.
> 
> Thank you for your useful comments on this up-to-now.
> 
> Best,
> 	Toby
> 
> -----
> 
> Toby D. Young (Adiunkt)
> Department of Computational Science
> Institute of Fundamental Technological Research
> Polish Academy of Science
> Room 206, ul. Swietokrzyska 21
> 00-049 Warszawa, POLAND
> 
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