Initialization of iterative solver

[Konrad Simon]

Dear deal.ii community,

I have a quick question: Suppose I know a vector that is close to the solution of my linear system. Is there a method to initialize an iterative solver with this vector?

Best,

Konrad

[Wolfgang Bangerth]

On 9/18/19 9:33 AM, Konrad Simon wrote:
>
> I have a quick question: Suppose I know a vector that is close to the
> solution of my linear system. Is there a method to initialize an
> iterative solver with this vector?

Yes, you just set the solution vector to your best guess before you pass
it to the solver. But you'll find that in practice, this rarely reduced
the number of iterations by any significant amount :-(

Best
W.

--
------------------------------------------------------------------------
Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

[Konrad Simon]

Yes, you just set the solution vector to your best guess before you pass
it to the solver. But you'll find that in practice, this rarely reduced
the number of iterations by any significant amount :-(

Many thanks, Wolfgang. Now, I also saw that in the source code of solver_cg.h. I really hoped that would speed up things a bit when solving time dependent problems.. Hm. 

Best,
Konrad