[petsc-users] left and right preconditioners

[hxie at umn.edu]

Hi,

Thanks. That is not easy for me. I will move the right preconditioner to 
the left which will lead to a similar preconditioned system with almost the 
same eigenvalues. Is there any example to do the multiplicative composite 
preconditioners on different preconditioner matrices from the original 
matrix?

Bests,
Hui 


------------------
Barry Smith bsmith at mcs.anl.gov
Sun May 23 13:13:59 CDT 2010

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   The PETSc Krylov methods are not coded to take directly both a left and 
right preconditioner. Therefor the way to use both left and right 
preconditioning together is to "fake" it by using a Mat that actually 
applies right preconditioner followed by the operator followed by the left 
preconditioner.

    Take a look at src/ksp/pc/impls/eisen/eisen.c and mimic that code. 
(basically copy all the subroutines and in that file and modify each one to 
your specific needs.)

    Barry

On May 23, 2010, at 1:01 PM, hxie at umn.edu wrote:

> Hi,
> 
> I want to use both left and right preconditioners for a linear system. 
> Both the preconditioners are based on part of the matrix. How can I 
> implement it? I can construct the preconditioner matrices. Thanks.
> 
> Bests,
> Hui