Add warp-cooperative CUDA kernel for DQN experience collection that
exploits H100's improved warp shuffle throughput. On sm_90+, 32 threads
(1 warp) cooperate on each dot product via __shfl_xor_sync butterfly
reduction, cutting per-thread register pressure from ~5.5KB to ~200B
and enabling full occupancy on 132 SMs.
Key additions:
- 6 warp-cooperative device functions in common_device_functions.cuh:
distributed/broadcast matvec (clean + NoisyNet), warp RMSNorm,
warp_reduce_sum_all
- 4 TILE_LAYER_WARP_* macros using __syncwarp() for warp-level sync
- 3 warp forward passes: standard dueling, NoisyNet, C51 distributional
(distributed heavy layers + broadcast atom layers for softmax)
- Full warp kernel: dqn_full_experience_kernel_warp with lane-0
simulation, strided state scatter, warp-shuffle curiosity gather
- Host-side compute capability detection (sm_major >= 9) with
automatic fallback to standard 256-thread kernel on older GPUs
- cuCtxSetLimit(STACK_SIZE, 16KB) for standard kernel safety
874/874 tests pass, 0 clippy warnings.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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