DLAHQR convergence problem

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DLAHQR convergence problem

Postby yokimi » Wed Jul 16, 2014 8:41 pm

Hi LAPACK developers,
I encountered a convergence problem of DLAHQR in V.3.5.0. However V.2.0 converged for the same problem.
I found a difference between two versions as shown below.

Version2.0
NH = IHI - ILO + 1
ITN = 30*NH
DO 130 ITS = 0, ITN

Version3.5.0
PARAMETER ( ITMAX = 30 )
DO 140 ITS = 0, ITMAX

ITN and ITMAX are the maximum number of QR iterations.
Modified V.3.5.0, where ITMAX is changed to ITMAX*NH, converged for the same matrix.
Is this a bug or intentionally changed?

Regards,
yokimi
yokimi
 
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Joined: Wed Jul 16, 2014 1:48 am

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