preconditioner for matrix-free linear system

[Barry Smith]

"PETSc's powerful preconditioners" are constructed from knowledge  
about the
matrix entries; if you do not provide any information about the matrix  
entries it cannot
construct any preconditioners. You need to provide the matrix as a  
PETSc  AIJ or BAIJ Mat
in order to use those preconditioners.

   Barry



On Apr 14, 2009, at 1:04 PM, Yongcheng Zhou wrote:

> hi there,
>
> I want to link my own package with PETSc in order to make use of its
> various preconditioners.  I am using
> matrix free method, so that I can directly refer the large matrix
> saved in my own format. The connection
> works OK without preconditioners, but runs into trouble when most of
> the preconditioners is called.
> For example, I got this message when using PCICC preconditionder:
>
> Matrix format shell does not have a built-in PETSc direct solver!
>
> So my question is how to utilize PETSc's powerful preconditioners for
> my matrix-free application.
>
> Thanks,
>
> Rocky