[petsc-users] SLEPc Eigenvalue problem - Zero Pivot

[Jose E. Roman]

Are you calling EPSSetFromOptions in your source code? 
Is your A-matrix also singular with a nullspace in common with B?
You can try with MUMPS as explained in section 3.4.1 of the users manual.
Also check that your matrices are the same as in Matlab.
Jose


El 14/05/2015, a las 08:52, venkatesh g escribió:

> Hi Jose, all,
> 
> I tried that too, it is telling the same error of "Detected Zero pivot in LU factorization". 
> My matrix B in AX=lambda BX has large no. of zeros and is singular. 
> 
> Is there another way ? 
> 
> Venkatesh
> 
> On Wed, May 13, 2015 at 9:02 PM, Jose E. Roman <jroman at dsic.upv.es> wrote:
> 
> El 13/05/2015, a las 17:28, venkatesh g escribió:
> 
> > Dear All,
> >
> > I am having a block matrix Eigenvalue problem AX = lambda BX
> >
> > My B is singular, it is a block matrix and only one block has non-zero values.
> >
> > Matlab Eigs is giving the result.
> >
> > I am using option: "./ex7 -f1 A1 -f2 B1 -st_type sinvert"
> >
> > Result is: Detected zero pivot in LU factorization.
> >
> > The ex7 is an example from SLEPc.
> >
> > Pls advice what to do ?
> >
> > cheers,
> > Venkatesh
> >
> >
> 
> If you know where your wanted eigenvalues are, set the target value, for instance:
> ./ex7 -f1 A1 -f2 B1 -st_type sinvert -eps_target 0.5
> 
> Jose
> 
>