[Trilinos-Users] BlockKrylovSchur: number of required Ritz vectors splits a complex conjugate pair.

Michael Junge junge at iam.uni-stuttgart.de
Thu Nov 27 23:45:45 MST 2008

Hi Heidi,
Yes you are right, a was using a modified version of the BKS in order to 
track the residuals in each iteration step. I modified my code as 
described, now it works just great!
Thanks a lot for your help!


Thornquist, Heidi K wrote:
> Hi Mike,
> Yes, it is easy to resolve this type of problem. The 
> Anasazi::BlockKrylovSchur class is only an iteration, so this type of 
> situation is normally handled by the solver manager class 
> (Anasazi::BlockKrylovSchurSolMgr).
> If you look at lines 596-613 of the BlockKrylovSchurSolMgr.hpp file, 
> you will see a block of code that gets the Ritz values and index from 
> the BlockKrylovSchur class, determines whether a conjugate pair is on 
> the boundary, and if necessary it modifies the number of Ritz pairs 
> the BlockKrylovSchur class computes by calling “setNumRitzVectors”. 
> From the error you received, it looks like you are working with a 
> modified code because the original solver manager should have caught 
> this problem and addressed it. So, you will want to have something 
> like the block of code in the BlockKrylovSchurSolMgr.hpp file to 
> address this situation.
> I hope this helps!
> Thanks,
> Heidi
> On 11/25/08 10:48 AM, "Michael Junge" <junge at iam.uni-stuttgart.de> wrote:
>     Hi,
>     when running the Block Krylov Schur solver of the trilinos package
>     8.0.3
>     for an unsymmetric eigenvalue problem, I get the error message
>     "Anasazi::BlockKrylovSchur::computeRitzVectors(): the number of
>     required
>     Ritz vectors splits a complex conjugate pair."
>     after the 6-th iteration.
>     Is there any possibility to cope with this error? Can I instead of
>     throwing this exception
>     lower the variable numRitzVecs_ by one and proceed without any
>     subsequent error?
>     Any suggestions to resolve this error are greatly appreciated.
>     Michael

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