feat(per-horizon-cfc): wire Controller A + Phase 1→2 transition in trainer
Per spec §2.3 + §3.1 and Task 9 of the plan.
Adds two device kernels to bucket_transition_kernels.cu:
- tau_change_frobenius_kernel: ‖tau_t − tau_{t-1}‖_F² via block-tree
reduction (no atomicAdd per feedback_no_atomicadd)
- slack_factor_apply_kernel: (Q1, Q3) → (Q1/slack, Q3*slack) where
slack = sqrt(Q3/Q1), ISV-derived per feedback_isv_for_adaptive_bounds
Adds to PerceptionTrainer:
- TrainingPhase enum (Phase1Warmup / Phase2Routed)
- ControllerA state machine instance
- prev_tau_d device buffer + tau_change_d + tau_change_staged mapped-pinned
- bucket_warmup_cap_override CLI diagnostic field
- bucket_routing_metadata stored after transition fires
- heads_w_skip_compact_d (HIDDEN_DIM floats) populated by transition
- Cached function handles for the two new kernels
Per-step in step_batched (Phase 1 only):
- Launch tau_change_frobenius_kernel → mapped-pinned scalar shadow
- DtoD prev_tau ← tau_all_d for next step
- Sync + host scalar read
- controller_a.update(tau_change, bucket_warmup_cap_override)
- On trigger: stage tau into scratch buffer (avoids in/out aliasing in
tau_reorder_kernel), execute_transition writes routing metadata +
reorders tau_all_d + populates heads_w_skip_compact_d,
slack_factor_apply widens IQR bounds, invalidate CUDA Graph,
latch phase = Phase2Routed, log via tracing::info.
Phase 2 dispatch + Controllers B/C/D wiring deferred to Tasks 10–12.
In Task 9's transient state, the trainer enters Phase 2 but continues
Phase 1 dispatch path; the reordered tau_all_d still produces a valid
forward pass since CfC's per-channel decay math is order-invariant.
Per pearl_no_host_branches_in_captured_graph: transition fires OUTSIDE
the captured graph (cached graph invalidated → recaptured next step).
Per pearl_cudarc_disable_event_tracking_for_graph_capture: event tracking
is already disabled trainer-wide; recapture on next step is safe.
Per feedback_no_htod_htoh_only_mapped_pinned: host scalar read goes via
mapped-pinned DtoD shadow, not bulk DtoH.
CLI: --bucket-warmup-cap-steps added to alpha_train (Option<u64>,
diagnostic override of Controller A's ISV-derived cap).
Tests: 7 GPU oracle tests pass on RTX 3050 (5 existing + 2 new for
Frobenius + slack_factor). 33 ml-alpha lib tests pass. Workspace
cargo check clean modulo pre-existing cupti / sp15 / gpu_per_integration
errors unrelated to this task.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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