parallelism

The backbone question of every frontier-lab infra loop. The answer that scores is organized around what each strategy communicates and how often, not just what it splits.

A reported DeepMind research-engineer question. The winning answer opens with a memory budget in bytes, not a list of parallelism buzzwords, here's the full arithmetic and the layout it forces.

A real infra-loop question that candidates fumble by guessing. The correct map, TP on NVLink, PP and DP across the scale-out fabric, falls out of three traffic profiles, and the reasoning is the answer.