Enable curiosity module by default (weight 0.0→0.1) to satisfy the
three-way gate (dueling + target + curiosity) that was blocking the
GPU experience collector CUDA kernel. This eliminates the 30-40% CPU
experience collection phase that was the main GPU idle bottleneck.
Additional changes:
- BatchSample API: train_step/compute_gradients now accept
Option<BatchSample> instead of Option<Vec<Experience>>, preserving
PER importance-sampling weights and indices through pre-sampling.
- Async PER pre-sampling: train_step_single_batch and
train_step_with_accumulation now pre-sample from the replay buffer
using a READ lock before acquiring the WRITE lock for GPU training.
This separates CPU sampling (~250μs) from GPU forward/backward (~3ms).
- Delete dead EpochPrefetcher: the binary (train_baseline_rl.rs) already
implements fold prefetching with background thread + mpsc channel +
GPU double-buffering, making the trainer's EpochPrefetcher redundant.
- Hyperopt DQN bounds: curiosity_weight min 0.0→0.01 so PSO can never
fully disable curiosity (which would re-gate the GPU collector).
10 files changed, -195 net lines. 2497 tests pass, 0 clippy warnings.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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