From jason at acm.org  Wed Mar 25 20:07:21 2009
From: jason at acm.org (Jason Riedy)
Date: Wed, 25 Mar 2009 15:07:21 -0400
Subject: [Rd] Listing of LAPACK error codes
In-Reply-To: <d3c1ff960903250629t7fcc5befn48f2bd25b2f54846@mail.gmail.com>
	("Orlando =?utf-8?Q?D=C3=B6hring=22's?= message of "Wed, 25 Mar 2009
	13:29:56 +0000")
References: <d3c1ff960903250629t7fcc5befn48f2bd25b2f54846@mail.gmail.com>
Message-ID: <87eiwl1kwm.fsf@sparse.dyndns.org>

And Orlando D?hring 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



[Rd] Listing of LAPACK error codes
Jason Riedy