[petsc-dev] Matrix Free Conjugate Gradient

[Jed Brown]

http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatShellSetOperation.html

Note that without an assembled matrix, you'll generally need to write your
own preconditioner, which you can do using PCShell.


On Fri, Nov 30, 2012 at 11:24 PM, Hesameddin Ilatikhameneh <
hilatikh at purdue.edu> wrote:

> Hello,
>
> We have a very large system (100M variables) which we want to minimize its
> energy. We are using Petsc extensively for matrix operations.
> I know that it is theoretically possible to use conjugate gradient method
> without storing Jacobian matrix (which is very huge in this case) since the
> conjugate gradient needs Jacobian times a vector not Jacobian itself.
>
> I read your manual about matrix free methods but I couldn't find where I
> can determine that function to Jacobian times a vector.
>
> I appreciate your help.
>
> Thanks
> Hesam
>
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