[petsc-users] "Must select a target sorting criterion if using shift-and-invert"

[Jose E. Roman]

Changed. Hope it is clear now.
https://bitbucket.org/slepc/slepc/commits/511900656a27a161c1df6fe2e42fd8d66d071800

Jose

> El 21 oct 2017, a las 14:27, Matthew Knepley <knepley at gmail.com> escribió:
> 
> On Sat, Oct 21, 2017 at 2:20 AM, Jose E. Roman <jroman at dsic.upv.es> wrote:
> This was added in 3.8 to check the common case when people incorrectly sets shift-and-invert with EPS_SMALLEST_MAGNITUDE. To compute smallest eigenvalues with shift-and-invert the correct way is to set target=0 and which=EPS_TARGET_MAGNITUDE. See for instance
> http://slepc.upv.es/documentation/current/src/eps/examples/tutorials/ex13.c.html
> 
> Jose, one thing we are trying to do in PETSc now is to give the options to fix a problem (or at least representative options)
> directly in the error message. Or maybe a pointer to the relevant manual or tutorial section. This gives users a hand up.
> 
>   Thanks,
> 
>      Matt
>  
> 
> Jose
> 
> 
> > El 21 oct 2017, a las 1:51, Matthew Knepley <knepley at gmail.com> escribió:
> >
> > On Fri, Oct 20, 2017 at 7:43 PM, Kong, Fande <fande.kong at inl.gov> wrote:
> > Hi All,
> >
> > I am trying to solve a generalized eigenvalue problem (using SLEPc) with "-eps_type krylovschur -st_type sinvert". I got an error message: "Must select a target sorting criterion if using shift-and-invert".
> >
> > Not sure how to proceed.  I do not quite understand this sentence.
> >
> > You need to know how to choose the shift. So for instance you want the smallest eigenvalues, or the closest to zero, etc.
> > I don't know the options, but they are in the manual.
> >
> >    Matt
> >
> >
> > Fande,
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> > -- Norbert Wiener
> >
> > https://www.cse.buffalo.edu/~knepley/
> 
> 
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/