Re: FLUKA-VMC Interface discontinued

From: Fluka Scientific Committee <>
Date: Sun, 28 Mar 2010 21:10:26 +0200 (CEST)

Answer of FSC to the message of Federico Carminati about discontinuining
the fluka-vmc interface:

Dear Federico,
                 thank you for your answer, that confirms indeed what
the FSC has found, namely that the FLUKA VMC interface is not
intended, and therefore not suitable, for a general use. That is also
why you were asked since the beginning to keep it within the ALICE
experiment, and that is why we were alarmed when we had signals that
other users were downloading the interface from the VMC site and
starting to use it for general purposes. The most alarming issue was
that one of the reasons why VMC was becoming popular is its supposed
easyness of use. Nothing can be less true. As detailed below, only a
very expert user may handle it safely outside the primordial ALICE
scope. For these reasons the FSC decided to continue the support for
ALICE and to discontinue it for all other users.

For what concerns bug reporting, we contacted you a first time in
November (as long as 4 months ago) and many times since, last one in
February. We always asked for a meeting with you or other developers,
since you (not us) are the expert on VMC, we are the experts on FLUKA,
therefore a fruitful debugging can only be done together. We are still
available for such a meeting.

Going to the details: About adding input cards: again this
demonstrates that the interface is not aimed for general purpose, to
such an extent that the only way to access the code capabilities is to
circumvent the interface. This is not at all evident for the general
user, who is usually confident in the performances of the VMC tool. In
addition, many of the cards are re-written runtime by the interface
itself, with the result that even the experienced FLUKA user will not
obtain what he wanted. Moreover, some of the FLUKA input options
would completely destroy the subsequent event-by-event analysis: think
to biasing for instance. Therefore, for what concerns the general
user, the VMC interface hides many of the FLUKA capabilities,
hides many of the problem-dependent settings, and may even screw
them up. Again, its use should be limited to the application for
which it has been built.

Without entering in a detailed point-by-point analysis of your message,
let us touch only a couple of examples for technical and physics issues
which illustrate what said above:

Technical examples:
Point 3): not with the VMC standard handling of the LOW-MAT card. This is
a typical example where the interface will prevent even the expert user
from doing what he likes/needs
Point 15): This is an example of why we should sit together, and why there
will always be misunderstadings when interfaces are built by people different
from code developers. Nowhere in the interface the FLUKA parameter which
forces a definite isotope is set. We thought it was a lack of a feature,
but from your answer we realize is probably a bug of the interface.
Point 17): not with the VMC standard handling of random seeds. By the way,
the RANDOMIZE card is always superseded runtime, and its use is at
odds with the macro. Of course, the expert user can change everything.

Physics example:
Point 12) Electro Magnetic Dissociation is not something relevant only for
a specific problem, rather it is important for cosmic rays as well and most
of all for all ion beams at LHC, ALICE included. This is an example how
critical decisions by the user are hidden by the interface
Point 13) the Birks' law cannot be applied a posteriori, it's a question
of physics. All the details of the energy deposition are needed to
compute it correctly

Concerning point 24) we are waiting for you since a long time.

About the gfortran version, ALICE got an expressly built gfortran
version in October 2009. Only at that moment the "-fPIC" problem
was discovered.

Finally, you write that you'll take no further action. However, we feel
once more important to urge you to come and discuss the problems we found
in the interface first of all in the interest of your experiment.

Since only a minority of the FLUKA users are interested in this discussion,
we would like to avoid to flood the list with further messages on this
topic. Whoever is interest in this discussion can contact us directly.

                 Best regards
            The Fluka Scientific Committee
Received on Mon Mar 29 2010 - 07:59:24 CEST

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