One-shot diagnostic to answer the SP13 root question: does the data have
predictable directional signal at the bar level?
Wires the existing `aux_next_bar_loss_reduce` kernel (which already had a
4-strip shmem reduction emitting `[dir_acc, pos_pred_frac, pos_label_frac]`
into a 3-float output) end-to-end:
- `gpu_aux_heads.rs`: launcher takes `dir_acc_out_ptr`, allocates 4×AUX_BLOCK
shmem to back the four parallel reductions.
- `gpu_dqn_trainer.rs`: adds `aux_nb_dir_acc_buf` (3 f32 device buffer),
threads it through the loss-reduce launch, exposes `read_aux_dir_acc()`
accessor for once-per-epoch DtoH readback.
- `training_loop.rs`: pins `aux_w = 1.0` (instead of the ISV-driven 0.05–0.3
clamp) so the supervised aux head dominates the loss; emits a new
`HEALTH_DIAG[ep]: aux_dir_acc accuracy=… pos_pred_frac=… pos_label_frac=…`
line per epoch.
Verdict thresholds:
* dir_acc > 55% by ep 5 ⇒ data has signal, DQN failing to use it
* dir_acc ≈ 50% throughout ⇒ data lacks signal at this timescale
* dir_acc 60–70% ⇒ strong signal we're not using
EXPERIMENT BRANCH — revert this commit after the investigation reads back the
5-epoch table from smoke logs. All five touch points are tagged
"SP13 data-investigation" / "EXPERIMENT" for clean revert.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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