Curious about cudaSetDoubleFor[Host/Device] Where does it apply?

I was looking through cuda_runtime_api.h and I noticed these 2 functions. Couldn’t find any reference to them anywhere and just thought I might get some ideas of what they do or when one might use them. Again, I’m just curious.

from the header:

extern __host__ cudaError_t CUDARTAPI cudaSetDoubleForDevice(double *d);

extern __host__ cudaError_t CUDARTAPI cudaSetDoubleForHost(double *d);