updated on June 18 2016

maintained by Julien Langou, U. Colorado Denver and Julie Langou, U. Tennessee




bug 159 DSTEMR - consolidates bugs 113 and 126


  • Present in LAPACK 3.6.0

  • Assigned to Osni.

  • Osni: We have a new subroutine to replace the subroutine causing us trouble.  We will be sitting together (OM and Prof. Parlett) tomorrow to discuss how this will behave.

  • I expect the new version of the subroutine will fix bug 113

  • 02/10/16 Osni: The bug has been traced to the factorization(s) performed by dlarrf.

  • The current implementation of dlarrf can lead to NaNs or element growth (this is expected) but the tests to deal with these cases are not working properly.

  • Beresford and I have experimented changing a few things in dlarrf, which fixes this bug and also bug 126, but we know that a more robust strategy needs to be devised. 

  • 2/11/16: We were able to trace the issue down here to the factorizations. We have some tests to cope with extreme growth in elements and NaNs,

  • but these tests are not robust. So we end up with linearly dependent eigenvectors when eigenvalues are close to each other.

  • 5/9/16: (Osni) We had a meeting in Berkeley (Prof. Parlett, Jim, Osni, I Dhillon) Some safeguards were removed over the years thinking we did not need them;

  • perhaps they must come back (this was the focus of our discussion). For some matrices, the vectors that are returned are not orthogonal the way we would

  • like them to be---the level of orthogonality is not ideal for nearly multiple eigenvalues. Prof Parlett and I will sit together to determine the best strategy for future LAPACK release.

bug 158 problem with DC SVD least squares


  • Present in LAPACK 3.6.0

  • Bug reported by Alexander Kobotov in 2015 to Julien

  • Problem of size ~22K with a large number of singular values close to 1.

  • dlasd7 fails to merge two sets of (very close) singular values together into a single sorted set, and subsequently dlasd4 (secular equation solver) fails to converge.

  • See email to LAPACK team

  • Assigned to Osni.

bug 130 :: Ambiguous lapacke interfaces to Cosine/Sine decomposition - 2 Trans parameters

bug 126 :: DSTEMR - misbehaviour of DLARRF

  • CONFIRMED on Jun 24th 2015

  • Present in LAPACK 3.5.0

  • Bug reported by Miroslav Ilias on Jun 27th

  • Link: http://icl.cs.utk.edu/lapack-forum/viewtopic.php?f=2&t=1820

  • Assigned to Osni

  • 02/10/16 Osni: The bug was originally thought to be related to splitting but is rather a misbehavior of DLARRF (in the presence of very tight eigenvalues); see bug 113.

  • SEE BUG 113 for all updates (will be closed along with 113)

bug116 :: ZGGEV fails but Matlab works

bug0061 :: zgehrd.f is overflowing


  • bug report by Victor Liu on Tuesday August 03rd, 2010

  • zgehrd.f is overflowing the maximum size in bytes of the largest array that

  • can be put on the stack with gfortran (⇒ leads ,e.g., to non-reproducible and uncorrect execution

  • of zgeev in multithreaded context

  • lapackers involved in the bug fix process: Julie and Julien Langou and Mathieu Faverge

  • bug fix by Victor Liu on Wednesday August 04th, 2010

  • Assigned to Julien (UC Denver) on Feb 11th 2015

  • see forum topic 1930

  • two outstanding issues: (1) how do we go to fix this?, (2) more LAPACK subroutines might be concerned.