vitess codes

[Kristian Nielsen]

> Date: Fri, 16 Jun 2000 11:54:17 +0200
> From: Geza Zsigmond <zsigmond at hmi.de>

Hi Geza,

Ok, I now have a first version of an automatic translation of McStas
components into VITESS modules. It seems to work quite well, but I will
need some help from you in testing it.

I found that the most convenient way to give you the translation program
is to make it part of McStas. I have therefore made a special "ALPHA"
version of McStas available for download at

    http://neutron.risoe.dk/mcstas/support/geza/mcstas-1.31A.tar.gz

Installation in any Linux system should be really simple (just the
single command "./configure && make install" should be sufficient). Note
that the translated McStas components should compile without problems on
Windows also; if not let me know and I will fix it.

Once installed, the new McStas command "mcstas2vitess" will read a
McStas component and automatically translate it into a corresponding
VITESS module. For example:

    cp /usr/local/lib/mcstas/samples/V_sample.comp .
    mcstas2vitess V_sample.comp

This will produce a number of files:

 - V_sample_VITESS.instr, a McStas instrument definition that implements
the corresponding VITESS module.
 - V_sample_VITESS.c, the instrument definition translated into ANSI C
(this could be compiled separately on Windows).
 - V_sample_VITESS, the compiled, executable VITESS module.
 - V_sample_VITESS.tcl, TCL code to be added the the VITESS file
vitess.tcl.

Optionally, the user may include a file V_sample.vif in the current
directy that mcstas2vitess will read. This file should consists of one
or more lines each with three words seperated by spaces. For example

    reflections -P string

The first word is the name of a parameter of the McStas component, the
second is the corresponding VITESS option name, and the third is either
`string' (for a string parameter) or `double' (for a numeric parameter,
which is the default). Parameters not listed in a .vif file will be
given suitable default VITESS option names and assumed to be numeric.

> The Tcl thing was made rather complicated (all compressed into the
> Vitess.tcl file) but in the next future we try to make it more
> accessible for the user, that is we want that the user can generate his

Actually, it turns out to be not so bad, and I sorted it out quite
easily even without knowledge of Tcl/Tk. My translator ouputs a comp.tcl
file which can be included in the vitess.tcl file. Only two more changes
in the vitess.tcl file are necessary: Add the translated module name to
the `AvailableSET' variable, and add a line giving the module executable
name in the `generateVitessCommand' function.

About the help-info I am not sure how to include that. I think VITESS
uses HTML documentation? In that case, we can just copy the HTML
generated automatically for all McStas components by the McDoc program
(see http://neutron.risoe.dk/mcstas/mcdoc/components/).

There is a significant difference between McStas and VITESS: In VITESS,
position and rotation of components is handled inside each module
(though you can also use the `frame' modules I guess). In McStas all
position and rotation is handled in the main engine outside the
components. The translation program adds position options (-x, -y, and
-z) to every translated module. Maybe there should also be automatic
rotation options for all modules? It is easy to implement but I think
you have more experience with this in VITESS and you should decide how
and if it should be done.

-----------------------------------------------------------------------

Anyway, I hope that you and the other VITESS people will now try the
translation program and see if you can get it to work. Please feel free
to ask any stupid questions that may come up if you have problems, and I
will try to help.

I tried myself to use some of the sample components of McStas in a
VITESS simulation, but I had difficulties sorting out how to get the
rotation of the crystal (theta and 2*theta) correct. I also tried
working from the VITESS crystaltest example, but for some reason that
did not work at all in the VITESS version I have (1.02).

Once you manage to run a successful VITESS simulation using an
automatically translated McStas component, we should announce it on the
SCANS mailing list. I think that would be taken as a great success of
the SCANS network.

 - Kristian.

--
Kristian Nielsen        kristian.nielsen at risoe.dk
Risø National Laboratory
Condensed Matter Physics and Chemistry Department
Tel. +45 4677 5515   Fax +45 4677 4790
Encryption PGP key http://neutron.risoe.dk/kn.txt