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foxhunt/docs
jgrusewski cf36091eeb spec+plan(dqn-v2): GPU drives, CPU reads (§4.C.6 revision)
User raised that the CPU-controller pattern (where CPU computes adaptive
values from ISV and writes back to ISV) violates the architectural
principle: GPU kernels should compute adaptive decisions; CPU-side code
is pure observation.

Replaces the AdaptiveController trait with read-only AdaptiveMonitor:
- No update() — CPU doesn't compute adaptive values.
- No write_output() — CPU doesn't write adaptive values to ISV.
- read() returns the GPU-computed value from ISV.
- diagnose() emits HEALTH_DIAG snapshot.
- observe() + fire_rate() track how often the GPU-computed value changes.

Reclassifies the 9 adaptive mechanisms:
- 6 reactive get GPU kernel + CPU monitor: atoms, gamma, kelly_cap, tau
  (Polyak EMA), epsilon, grad_balancer (last is already GPU-driven).
- 3 static get ISV constructor-write, no monitor: cql_alpha,
  conviction_floor, plan_threshold.

New ISV slots for GPU-written adaptive outputs (EPSILON_EFF, TAU_EFF,
GAMMA_EFF, KELLY_CAP_EFF) and CPU-born inputs (EPOCH_IDX, TOTAL_EPOCHS),
plus slots for the 3 static configs.

Rationale:
- Unified adaptive machinery, no CPU-side special cases.
- Per-sample granularity available (Expected SARSA τ in c51_loss_kernel
  is already the exemplar — reads ISV q_gap + health per sample).
- Zero CPU→GPU config transfer in any path.
- ISV is single source of truth for every adaptive value.

Plan 1 Tasks 8-17 restructured:
- Task 8 creates AdaptiveMonitor trait (not AdaptiveController).
- Tasks 9, 10, 11, 13, 14, 17: GPU kernel + monitor pairs.
- Tasks 12, 15, 16: static ISV writes only.

Follow-up commits will revert Batch A (d76849f31) and Batch B (4189da563)
which implemented the old CPU-compute pattern, then re-implement under
this design.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-24 16:20:24 +02:00
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