GPU Clusters and Schedulers
A GPU on a shared cluster isn't just requested and used the way a local one is — a scheduler decides which physical devices a job gets, renumbers them from the job's point of view, and (on Kubernetes) treats them as an indivisible resource unless something extra is configured. Getting any of this wrong tends to look like a correctness bug — a job silently touching the wrong device, or "no GPUs available" on a node that clearly has some — rather than an obvious scheduling error.