[Rd] Listing of LAPACK error codes

[Jason Riedy]

And Orlando Döhring writes:
> Is there a listing for the error codes from Lapack routine 'dsyevr'?

The HTML-ized LAPACK functions are at http://www.netlib.org/lapack/explore-html/
although they may lag behind releases a little bit.  The page for
dsyevr.f is:
  http://www.netlib.org/lapack/explore-html/dsyevr.f.html

And the LAPACK mailing list is at lapack at cs.utk.edu, although as
with all such projects, responses may be a *long* time in coming.

> Especially I am interested about the meaning and handling of error codes 1
> and 2.

The high-level drivers like DSYEVR dispatch to different internal
routines depending on what was requested.  That makes documenting the
error codes a little painful...

For some of the routines involved, INFO.eq.1 or 2 implies 1 or 2
entries didn't converge, either when reducing a tridiagonal to
diagonal, in bisection, or in inverse iteration.  For another, but
only if you're requesting the ilo-th through ihi-th eigenvalues, 2
would imply non-monotonic arithmetic, and I would be *very*
surprised.

So likely something somewhere didn't converge.  Picking parameters
that *always* converge for eigenvalues is an open problem.

Have you tried this on different platforms, or with different BLAS?
Can you release the data that causes the problem?

Jason