Spatially uniform DMI and subregions

[lang-m]

Specifying the value of D for DMI with a real number produces an error when subregions are defined for the mesh.

Example:

• mesh with two subregions fixed1 and fixed2 (to fix cells during minimisation)
• uniform DMI defined via mm.DMI(D=..., ...)
• Error message: Error thrown from inside "Oxs_ExtCreateAndRegister" --- Incomplete or incorrect initialization --- Oxs_Ext initialization error in construction of Oxs_DMI_T:dmi --- Oxs_Ext ERROR in object Oxs_DMI_T:dmi: First entry in D[0] sub-list, "main", is not a known region in atlas "Oxs_MultiAtlas:main_atlas". Second entry in D[0] sub-list, "main", is not a known region in atlas "Oxs_MultiAtlas:main_atlas". Known regions: universe fixed1 fixed2

[lang-m]

As a workaround specifying D with a dictionary, e.g. mm.DMI(D={'default': ..., 'fixed1': ...}, ...) is working.

At least one of the subregions must be specified explicitly in the dictionary. D={'default': ...} produces this error: Error thrown from inside "Oxs_ExtCreateAndRegister" --- Incomplete or incorrect initialization --- Oxs_Ext initialization error in construction of Oxs_DMI_T:dmi --- Oxs_Ext ERROR in object Oxs_DMI_T:dmi: Empty parameter list for key "D"

[lang-m]

The region "main" used for real D: https://github.com/ubermag/oommfc/blob/7265ef839073d9aaf3ff103fcd1cfff489b986c4/oommfc/scripts/energy.py#L189-L195 is only specified when the mesh has no subregions: https://github.com/ubermag/oommfc/blob/7265ef839073d9aaf3ff103fcd1cfff489b986c4/oommfc/scripts/mesh.py#L21-L25