[petsc-users] Is there efficeint method for matrix with one extremely small eigen value?

[Jed Brown]

On Wed, 06 Apr 2011 17:06:40 +0200, Umut Tabak <u.tabak at tudelft.nl> wrote:
> On 04/06/2011 04:50 PM, Jed Brown wrote:
> > On Wed, 06 Apr 2011 16:37:26 +0200, Umut Tabak <u.tabak at tudelft.nl> 
> > wrote:
> >> Just curious, are not the other negative eigenvalues problematic as 
> >> well?
> >
> > Negative eigenvalues do not pose any particular problem to Krylov 
> > methods like GMRES. Conjugate gradients does require that the matrix 
> > be SPD, but petsc-dev detects when a matrix is negative definite and 
> > still does the right thing. 
> 
> Also with cg type methods? if yes, how?

http://petsc.cs.iit.edu/petsc/petsc-dev/rev/cae94ca39fcb