[pocl-devel] device pointer for NVIDIA + MPI systems

[Noah R. <noa...@gm...>]

Hi All,

    I'm trying to find a working method, or short-term hack of a working
method, to adapt my OpenCL application to run well on contemporary HPC
systems with NVIDIA GPUs. (i.e. Perlmutter at NERSC)

For this, I want or need to use GPU-side device pointers in the Message
Passing Interface (MPI) arguments for communication between nodes on the
supercomputer.

As far as I can tell, OpenCL provides no mechanism to obtain the
device-side memory pointer for either a cl_mem buffer object or SVM
allocation.
I would need this pointer to use with MPI calls.

In CUDA-based prototype codes, this type of MPI use to/from GPU memory is
straightforward because cudaMaloc() returns a device pointer that is
accepted in MPI_xyz() calls.

Has anyone tried something like this with POCL using the CUDA backend?
Or is there familiarity with the implementation that would suggest how to
get at this device pointer from a cl_mem object ?

Cheers,
-Noah