Path (B) Commit B — load-bearing semantic change for the SP19 multi-
horizon reward augmentation. At fxcache-write time, blend 1-bar / 5-bar
/ 30-bar log-returns into `tgt[1]` (`preproc_next`) using equal-thirds
weights with `1/sqrt(N)` vol-scale correction:
blended = (1/3) * r_1
+ (1/3) * r_5 / sqrt(5)
+ (1/3) * r_30 / sqrt(30)
The vol-scale correction applies INSIDE the blend (before weighting) so
each horizon's log-return is at unit-volatility-equivalent under
random-walk assumption — drops naturally into the existing `tgt[1]`
preprocessing pipeline (consumed in `experience_kernels.cu:1556` and
`cuda_pipeline/mod.rs:508`) without double-scaling.
Producer trim: valid range shrinks by `LOOKAHEAD_HORIZON_MAX = 30`
bars since `r_30` needs `close[i + WARMUP + 30]`. Walk-forward fold
construction is dataset-relative, so trimming at producer time shifts
every fold's tail by 30 bars — one-time cost per fxcache regen.
Both producer call sites (`precompute_features.rs` for the
feature-precompute binary, `data_loading.rs` for the DBN-fallback
in-process path) change atomically per `feedback_no_partial_refactor`.
Kernel consumers are unchanged — only `tgt[1]`'s value composition
differs from the consumer's perspective.
ISV slots [507..510) (allocated in Commit A) are NOT consumed at
producer time — `precompute_features` runs BEFORE training so the
ISV bus isn't initialised when the blend happens. Producer hardcodes
1/3 each via `SP19_HORIZON_BLEND_WEIGHTS`. Future Path (A) refactor
would bump TARGET_DIM to carry per-horizon log-returns and read
ISV at training-step time; for the empirical hypothesis test
("does multi-horizon blend lift WR?") equal-thirds is sufficient.
fxcache schema invalidation: `FXCACHE_VERSION` 8 → 9. Existing
`.fxcache` files (1-bar-only `preproc_next`) fail validation at load
and trigger Argo's ensure-fxcache regen step. First L40S run after
this commit takes ~10-15 min longer for the regen — one-time cost,
expected.
Touches:
- crates/ml/examples/precompute_features.rs: SP19_HORIZON_BLEND_WEIGHTS
constant + LOOKAHEAD_HORIZON_MAX trim + blend in tgt[] writer +
early-bail-out check on minimum dataset size.
- crates/ml/src/trainers/dqn/data_loading.rs: same blend +
trim in DBN-fallback path; `last sample targets itself` block
removed (the trimmed range guarantees feature-vector and target
lengths match without a sentinel last row).
- crates/ml/src/fxcache.rs: FXCACHE_VERSION 8 → 9 + v9 docstring entry.
- crates/ml/tests/multi_horizon_reward_blend_test.rs (NEW): CPU-only
oracle behavioural test — 4 cases including known returns, trim
contract, zero-close short-circuit, constant-price blend.
- docs/dqn-wire-up-audit.md: Concerns subsection appended to the
SP19 Commit B entry already drafted in Commit A (pre-existing
test_fxcache_empty + test_dqn_checkpoint_round_trip flakiness
documented for Invariant 7).
Verification:
SQLX_OFFLINE=true CUDA_COMPUTE_CAP=86 cargo check --workspace clean
cargo test -p ml --test multi_horizon_reward_blend_test 4/4 pass
cargo test -p ml --test fxcache_roundtrip_test test_fxcache_f32_roundtrip passes (TARGET_DIM unchanged)
cargo test -p ml --lib ... 13 baseline failures (pre-existing); zero new regressions
bash scripts/audit_sp18_consumers.sh --check exit 0
Pre-existing test_fxcache_empty failure: hand-crafts a 64-byte header
but the actual header is 72 bytes; reader bails early on
"failed to fill whole buffer" instead of "bar_count=0". Test setup
bug, NOT a regression. Pre-Commit B failure count: 13. Post-Commit B
failure count: 13 (the test_dqn_checkpoint_round_trip test is flaky
and toggles independently of this change — verified by stashing and
re-running 3× pre-Commit B).
Atomic-refactor invariant satisfied: Commit A (slot reservations) +
Commit B (producer-side blend) land on the same branch with no L40S
dispatch between. Per task instruction the branch stays unpushed
pending user review.
DBN-fallback path: applied identically in `data_loading.rs:497-528`.
Both producers use the same `SP19_HORIZON_BLEND_WEIGHTS` constant and
the same `LOOKAHEAD_HORIZON_MAX = 30` trim.
Vol-scale correction site: applied inside the blend (before weighting)
in BOTH producers. The existing `tgt[1]` preprocessing pipeline does
NOT double-scale — `experience_kernels.cu:1556` and
`cuda_pipeline/mod.rs:508` consume `tgt[1]` as a unit-scale log-return
exactly as before the blend was added; the blended value drops in
without further scaling.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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