Using real_t for toMatrix does not work with types that are not real_t

Within the file hog/operator_generation/kernel_types.py a generic field called mat is created and its dtype is set to real_t. This only works if everything is real_t, when you want to use other types, e.g. for mixed precision, compile errors occur, since real_t (usually float64) cannot be converted to a 'smaller' type.

cannot convert 'walberla::real_t*' {aka 'double*'} to 'const float*'

The question is, what is the desired behavior. I understand that the signature is given as real_t and maybe it is mathematically advised to even use float64, but this way it is not possible to experiment with different precisions.

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Code part of interest (kernel_types.py line 268 to 276) link-to-code:

# NOTE: The type is 'hyteg_type().pystencils_type', i.e. `real_t`
#       (not `self._type_descriptor.pystencils_type`)
#       because this function is implemented manually in HyTeG with
#       this signature. Passing `np.float64` is not ideal (if `real_t !=
#       double`) but it makes sure that casts are inserted if necessary
#       (though some might be superfluous).
mat = create_generic_fields( ["mat"], dtype=hyteg_type(HOGPrecision.REAL_T).pystencils_type )[0]