LAPACK Archives

[Lapack] question about ZHGEQZ for 2x2 block


I am working on GGEV code. But I found ZGGEV failed to converge in one
sample. I found it is similar to what has been reported in this
mailing-list. Do we have any update for this problem?

With more debug print output, I think ZHGEQZ failed to converge because it
can't get eigenvalue for the 2x2 block. There is a difference between
DHGEQZ and ZHGEQZ.  DHGEQZ has special code to handle the 2x2 block but
ZHGEQZ doesn't. Is there any special consideration about this in C/ZHGEQZ?
As what I found in debug output, the implicit sweep doesn't change the 2x2
block (H is 2x2 and T is 2x2 upper triangular) even with exceptional shift.
So it failed to converge.

Best Regards!
Peng HongBo
-------------- next part --------------
An HTML attachment was scrubbed...

<Prev in Thread] Current Thread [Next in Thread>

For additional information you may use the LAPACK/ScaLAPACK Forum.
Or one of the mailing lists, or