Reply To: Multi-GPU usage issue
It looks to me as if only one MPI task is launched per node in your SLURM script. You can try to include a #SBATCH --tasks-per-node=8 setting.
If your application case calculates the number of cuboids w.r.t. the number of MPI processes (this is the case for OpenLB’s example cases) you do not need to manually change this to 8.
Edit: Enabling handling of more than one GPU by a single process would be a nice addition and require setting the active device via CUDA as you indicated. However this is not included in OpenLB 1.5 – there we assume that each process that hold a GPU-based block lattice has access to exactly one default GPU (as configured via the visible device environment variable)