[petsc-users] Problems with preconditioners, which one?

[Filippo Spiga]

  Dear Matthew,

Matthew Knepley wrote:
> Actually, I strongly disagree. Preconditioners are very problem 
> specific, and it is often impossible
> to prove which one will work for a certain problem. There are many 
> well-known results along these
> lines, such as the paper of Greenbaum, Strakos, and Ptak on GMRES. 
> Experimentation is essential.

In principle I agree with you: experimentations are essentials. But only 
if you know the "path", if you know what are you doing. Before wrote my 
first email, I tried to so something for two days: I checked the method, 
I checked the code, I tried to verify the problem in other ways. But my 
knowledge about the solvers and the library is limited so trying to 
continue to do experimentations would has been useless. Then I decided 
to consult experts (-:

-- 

Filippo SPIGA

«Nobody will drive us out of Cantor's paradise.»
      -- David Hilbert