[mcstas-users] [McStas 2.7] Pol_FieldBox with tabled magnetic field

[Erik B Knudsen]

Dear Nicola,
Thank you for the report. This ought to work, but I will take another 
look at the instrument you kindly supplied, and report back.

The first warning message about macros and whitespace can safely be 
ignored. I merely means, that strictly speaking, the generated code does 
not quite adhere to the c99-standard, in that some macros do not end up 
having correct whitespace.

...but for the real issue - hang on and I will report back soon.
cheers
Erik

On 13/12/2020 17:22, MARTIN Nicolas wrote:
> Dear McStas users,
> 
> I am currently trying to simulate the effect of a guide field on the 
> beam polarization of a SANS instrument, using McStas 2.7 on Windows 10 
> 64 bits.
> 
> To that end, I calculate this field analytically on a regular 3D grid 
> and export the output in an ASCII text file.
> 
> This file is then used as the argument of a /Pol_FieldBox/ component.
> 
> 
> My test instrument is compiling well, besides the following warning message:
> 
> 
> C:\mcstas-2.7\lib\tools\Python\mcrun\..\mccodelib\..\..\..\optics\Pol_FieldBox.comp: 
> At top level:
> 
> C:\mcstas-2.7\lib\tools\Python\mcrun\..\mccodelib\..\..\..\optics\Pol_FieldBox.comp:76:19: 
> warning: ISO C99 requires whitespace after the macro name
> 
> ((double *)field_parameters)[2]=Bz;
> 
> 
> Note that this doesn't prevent me from accessing the "/Start 
> simulation/" window of the /mcgui/.
> 
> Although McStas seems to read the content of my field file correctly 
> (number of points and step sizes are OK), I get the following error 
> message when trying to perform the simulation:
> 
> Opening input file 'fieldbox.dat' (Table_Read_Offset)
> interpolator_load: Axis 0: step=0.004, unique values=12220, from file 
> 'fieldbox.dat'.
> interpolator_load: Axis 1: step=0.004, unique values=1110, from file 
> 'fieldbox.dat'.
> interpolator_load: Axis 2: step=0.004, unique values=100, from file 
> 'fieldbox.dat'.
> interpolator: file 'fieldbox.dat' with 12221 points. Space is 3D, Field 
> is 3D. Using method 'kdtree'.
> interpolator_interpolate: ERROR: invalid interpolator method  from file 
> 'fieldbox.dat'.
> 
> The result is exactly the same with the "/flipfield.dat/" file (provided 
> in the "/\\mcstas-2.7\lib\data/" folder).
> 
> 
> My instrument and field files are attached to this e-mail.
> 
> 
> Has anyone already encountered this interpolator issue? Any clue to fix it?
> 
> Should I arrange my input data in a different way? Use a different 
> number of decimal places?
> 
> 
> Many thanks in advance for your help, kind regards,
> 
> Nicolas
> 
> _______________________________
> Dr. Nicolas MARTIN
> Laboratoire Léon Brillouin
> UMR12 CEA-CNRS
> Bât 563 CEA Saclay - p. 105
> 91191 Gif-sur-Yvette Cedex
> France
> _/E-mail:/_ nicolas.martin at cea.fr <mailto:nicolas.martin at cea.fr> / 
> nicolas.martin84 at gmail.com <mailto:nicolas.martin84 at gmail.com>
> 
> _______________________________________________
> mcstas-users mailing list
> mcstas-users at mcstas.org
> https://mailman2.mcstas.org/mailman/listinfo/mcstas-users
> 

-- 
Erik Bergbäck Knudsen, Research Engineer         | DTU | morituri
NEXMAP, DTU Fysik, DK-2800 Kgs. Lyngby, Denmark  |<>-<>|    te
phone: (+45) 2132 6655                           |<>-<>| salutant