If you have compiled GPU-compatible operators (which requires a
Nvidia GPU and CUDA), you can call the function rkeops_use_gpu()
to specifically run computations on GPU.
It is recommended to use default GPU (i.e. device = -1 or 0) and
manage GPU assignment outside R by setting the environment variable
CUDA_VISIBLE_DEVICES.
Note: The default behavior in rkeops is to use CPU computing, thus
calling the function rkeops_use_gpu() is mandatory to run
computations on GPU.
To disable GPU computing, run rkeops_use_cpu().