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

[Fande Kong]

Thanks Jose,

I like this change.

Fande

On Mon, Oct 23, 2017 at 10:03 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Oct 23, 2017 at 11:18 AM, Jose E. Roman <jroman at dsic.upv.es>
> wrote:
>
>> Changed. Hope it is clear now.
>> https://bitbucket.org/slepc/slepc/commits/511900656a27a161c1
>> df6fe2e42fd8d66d071800
>
>
> Great, that is much clearer.
>
>   Thanks,
>
>      Matt
>
>
>>
>> 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/
>>
>>
>
>
> --
> 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/ <http://www.caam.rice.edu/~mk51/>
>
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