[Ifeffit] FEFF report: Hard tests failed in fovrg.

Kevin Jorissen kevinjorissenpdx at gmail.com
Wed Aug 7 14:27:21 CDT 2013

Hi Bruce,

thanks for your answer.

I'm glad that we seem to be in agreement about the main point, which is
that a FEFF9L is the best way forward (integrates with analysis tools; has
all improvements and bugfixes; free).  I'll fire up developer communication
about this (including you).

Thank you for bringing the $$ problem to my attention; I did not know that
it was a problem for a large number of users.

As for the original question, the algorithm "fovrg" had some problems
(meaning that it would fail; not that it would produce bad results), as
explained by John Rehr in the 2005 message cited by the OP.  The needed
improvements are exactly those changes made in later versions.  That is why
I am more drawn to a FEFF9L than to fitting some of the improvements into
the old FEFF6L, but I will discuss it with the other developers.

I have not tried to make the OP's files work in FEFF6L.  I would look at
the RGRID/AFOLP/FOLP/POTENTIALS cards first.  I'll give this a try later
myself, but it's possible that there is no solution within FEFF6L.

Let me finish by reiterating that people are welcome to contact us directly
with FEFF questions, as we may not see all messages reported here.



On Wed, Aug 7, 2013 at 11:58 AM, Bruce Ravel <bravel at bnl.gov> wrote:

> Kevin,
> Thank you for your email.  I apologize if I expressed myself in a way
> that was too mean-spirited in my earlier email, but the basic point
> was true.  The "hard test in fovrg" question has been asked
> repeatedly.  Your response today is, by my memory, the first we've
> seen on this topic, from your group, and on this mailing list.
> I have a few comments.
>  1. The original question remains unanswered.
>  2. A lot of people use the software stack at the top of which Artemis
>     sits.  For many of those people a $250 or $500 expense is
>     completely out of reach.  Not a few.  Lots.  We have users who are
>     impoverished grad students.  We have users who are researchers in
>     developing countries.  To be so blithe about a $500 expense is
>     unfair to those people.
>  3. Feff6 is unambiguously not dead.  Feff6L is the only version (the
>     *ONLY* version) I am allowed to package with my software.  That
>     not only makes it alive -- it makes it the de-facto version for
>     many people.
>  4. Is Feff9L a thing?  I would be thrilled to put Feff6L out of our
>     misery and replace it with something that post-dates Windows 95.
>     I agree that it has been discussed, but no one has ever asked me
>     to take a look at such a thing.  Perhaps I flatter myself, but I
>     would think that I would be involved somehow, given that one of
>     the main reasons to make Feff9L is to see it included in a package
>     with Artemis.
> So, let me end this on a positive note by reaching out to you with
> some actionable questions:
>   1. What should I tell my users who ask about the hard test failure
>      in fovrg that is not a solicitation to spend money on Feff9?
>   2. Can I take a look at Feff9L?
> Cheers,
> B
> On 08/07/2013 02:29 PM, Kevin Jorissen wrote:
>> Dear Ifeffit community,
>> a short reaction from the FEFFgroup.
>> 1/  It's true that we don't follow up on the ifeffit ML 100%.  Important
>> issues usually do get through to us.  We highly value the ifeffit
>> community.  We can also be contacted directly for problems that are FEFF
>> related rather than iFEFFit related ( contact
>> <http://www.feffproject.org/**feffproject-contact.html<http://www.feffproject.org/feffproject-contact.html>>
>> ).  We'll likely
>> ask you for the feff.inp file that generates the problem.
>> 2/  We're glad that FEFF6 is so successful.  Meanwhile FEFF6 is about as
>> old as Windows95, and development is now focused on FEFF9
>> <http://www.feffproject.org/**feffproject-feff.html<http://www.feffproject.org/feffproject-feff.html>>,
>> which has 15-20
>> years of improvements over FEFF6.  It's a big improvement for anyone
>> running FEFF calculations.  It costs $500, or $250 upgrade from any paid
>> version of FEFF.
>> 3/  The OP posted 5 input files.  4 of these run without problems in
>> FEFF9.  The last has I atoms (Z=53) at a spacing of 0.8A, and doesn't
>> run out of the box.  I expect the same result from FEFF8.
>> 4/  There has been some effort to bring a "FEFF9lite" to the analysis
>> codes, analogous to the FEFF6lite discussed here.  We would be very
>> happy to see that effort succeed.
>> 5/  FWIW the fovrg routine was retired in 1996 and replaced by a
>> relativistic version called "dfovrg".  The "hard error" does not exist
>> anymore.
>> 6/  We're a small team; we apologize for all the 'bothering' we don't
>> get around to.  We do care about supporting our users and put a lot of
>> energy into support.  Please reach out ot us when you need us.
> --
>  Bruce Ravel  ------------------------------**------ bravel at bnl.gov
>  National Institute of Standards and Technology
>  Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2
>  Building 535A
>  Upton NY, 11973
>  Homepage:    http://xafs.org/BruceRavel
>  Software:    https://github.com/bruceravel
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